Monday, February 11, 2013
Spark Plugs, Wires & Coils
A member of one of the Mustang forums asked me "What are your thoughts about performance plugs, wires, and coils? These are usually relatively cheap and obviously bolt-on. Advertisements always emphasize the gains achieved with these items."
This was my response...
Simple answer, they are lying to you.
Regarding spark plugs let us first examine what motivation Ford would have to choose to install plain ol' single electrode platinum plugs, rather than some other fancy magical multi-electrode, mystical "power" plug.
Answer: They have none.
Auto makers compete vigorously to attain the highest horsepower and fuel economy ratings, and have to pay a fine to the EPA for every vehicle produced that does not meet the CAFE requirements. If spending another $50 on spark plugs could provide such miraculous increases in HP and mpg it would be pretty stupid of them to not do it, wouldn't it? Also consider that Champion has been making spark plugs for over 110 years and with the exception of a small line of multi-electrode designs for specialty applications they do not make such plugs for general automotive use. If there were a better way to make a spark plug Champion would have sorted it out by now, or bought up the technology.
So, for nearly any but the most radical naturally aspirated build, and any modest boost (< 15 psi) setup, fine wire precious metal electrode plugs are the best selection. Fine wire plugs require 40% less voltage to ionise the gap and fire, and are much less prone to fouling--that is why automakers choose them. I run Champion stk# 3401 plugs in my '03 GT which turned out 262/305 rwHP/lb-ft with only modest bolts-ons and a highly optimised tune.
Plug Wires, Coils and Coil Packs:
A long long time ago, in a Galaxy far away (a 1964 Ford Galaxy) stock ignition coils sucked big time when combined with almost any sort of engine performance upgrade; as did the distributor, condenser and wires--and an entire industry was built around this, by companies like Accel, Mallory, MSD and others, to fill the gap (no pun intended).
Back then the grandiose claims made by aftermarket ignition component makers/vendors were actually and very largely true. But then along came emissions standards and the automakers could no longer afford to deliver vehicles with such poor ignition systems; and meet the standards. For a while the aftermarket stuff was often still superior, however as time went by and OEM distributorless wasted spark and COP ignition systems became commonplace the aftermarket claims became increasingly just that--claims based on something that was once true ( BTW, K&N lives on riding this same train).
Assuming that wire set/coil combination A can fire the plugs so as to initiate a solid combustion and flame-front, there is no reason to expect that wire set/coil combination B could cause engine output to increase. Beyond that distributorless technology (coil packs and long plug wires) for over the road vehicles are a far less than state-of-the-art systems. If I were doing a serious street build on a '96 to '98 Mustang with the EDIS system I would look into a COP conversion.
Now there is something serious to discuss.
The stock COPs are universally held as being superior to aftermarket units, and my own testing of COPs donated to my project supports that position. I found no aftermarket COP that surpassed the stock units in either energy output or durability, in fact a number of the aftermarket COPs were less durable:
The COP Tester shown is my own creation and uses a manually triggered MOSFET ignition driver firing circuit very similar to that in the PCM. The COP's output is connected to an adjustable air gap tester, and its output gauged by how large an air gap it can fire across:
Here is an Accel COP set up for testing:
Here are the results of testing four Accel COPs against four stock coils:
Note that the Ford OEM COPs consistently produced 55 kV, 5 kV more than the Accel COPs.
Here is a video of an Accel COP being tested, firing across a 15 mm (0.590") air gap.
If the rapid sequential full charge dump firing shown in the video were performed 10 to 12 times the COP will become so hot you could not hold it in your hand; if full charge dump is fired 20 times rapidly smoke will start to come from the COP and it will have been significantly compromised. 25+ such firings will burn the COP out completely. At some number of such firing this is true for any COP, from any maker. I did find that in general the stock COPs were more resistant to this treatment, some requiring as many as 30 rapid cycle firings to burn them out.
This is a real torture test as the COPs are not engineered or intended to ever do this. In normal use, making a spark across a piddly little 1.4 mm (0.054"), less than 5% of the COPs full charge is dissipated. Here's are oscilloscope traces of an Accel COP firing across a 0.054" and 15 mm gaps:
Note: I more aggressively and destructively tested the Accel COPs because a contributor sent me a set of eight (with three already burned out) and I have my own set of eight in which four had burned out over a five week period, with between 20k and 25k miles on them.
COPs have tremendous reserve capacity, so much that it is used at idle and up to 1200 rpm or so to fire each plug 3 times in rapid succession to provide a smoother burn and improve emissions. Here is what this looks like on an oscilloscope:
The high initial spike represents the coil's stored energy ionising the spark plug gap, this is a voltage spike of 16 to 20 kV (off the top of the trace). The short downward sloping line after the ionisation event is the plug actually firing at a sustained voltage of 4 to 6 kV. The triple firings are clearly seen at 1.33 ms intervals.
The torture test also reveals why COPs tend to fail soon after washing an engine or a coolant leak has flooded the plug wells. The COPs will be have been compromised by being subjected to near and full capacity discharges. Grossly worn plugs with large gaps, and boots that are arcing through can also weaken COPs; I recommend changing the COP boots at 100k miles.
So there you have it--see what happens when you ask a retired engineer a simple question?
Wednesday, June 20, 2012
Hydraulic vs. Cable Operated Clutch Actuation--Clearing Up the Myth:
I received an email asking about hydraulic clutch conversion in which the author asked questions indicating an unclear understanding of what could be accomplished by such a conversion. The most significant being that it could somehow magically reduce the pedal pressure and throw vs. the cable operated clutch--unfortunately it just ain't so.
First so that we can all be on the same page, here is a diagram of the clutch control group used on the 1994 through 2004 Mustangs:
The OEM cable clutch actuation mechanism has an overall mechanical advantage, from the pedal to the throwout bearing, very close to 10:1. I.e. 5 to 6 inches of pedal travel produces the 0.5 to 0.6 inches travel needed to disengage the clutch at the TOB. On my '03 with a RAM HDX clutch I found it requires 45 lbs of pedal pressure to accomplish this, or assuming 6.0 in of pedal travel, some:
45 lbs * 6 in = 270.0 in-lb of work at the pedal
Because of the 10:1 mechanical advantage that 45 lbs of pressure applied to the pedal creates 450 lbs of pressure at the TOB (ignoring friction in the actuating mechanism), and the 6.0" travel makes the TOB move 0.6".
450 lbs * 0.6 in = 270 in-lbs of work at the throwout bearing
Other clutches will of course require different amounts of work to actuate, however that the work applied at the pedal equals the work applied at the TOB is inescapable (again ignoring friction in the actuator).
AND, it doesn't matter how you get that work from your foot to the TOB. You could reduce the pedal travel to 3 in and increase the pressure to 90 lbs, or increase pedal travel to 12 in and reduce the required pressure to 22.5 lbs; it doesn't matter which, it will still take 270 in-lbs of work.
It also doesn't matter what sort of mechanism (I will one last time ignore frictional losses, but we'll get to that in a bit), a cable or hydraulic master/slave cylinders, you use to transfer the work.
OK, now let's look at hydraulic actuation of the clutch in our cars, using this kit from McLeod Racing),
McLeod does not provide full specs for their TOB however typically they provide maximum travel of 0.700", and a piston area of 1.25 in². It will still take the same 450 lbs of force to disengage the clutch, so we can calculate that we'll need the hydraulic pressure applied to the TOB to be:
450 lbs / 1.25 in² = 360 psi.
To make things simple for now let's work with a master cylinder having a 1.00 in² piston. Obviously with 1 in² pistion it would take 360 lbs of force to create 360 psi, and we would need a pedal with a 8:1 mechanical advantage to get back to the 45 lbs of force the cable clutch required:
360 lbs / 8 = 45 lbs
Now let's look at how far that pedal will need to travel. The same 0.6 in TOB movement is needed so we will need to move 1.25 in² * 0.6 in = 0.75 cubic inches of fluid. To move 0.75 in³ of fluid the 1 in² master cylinder piston will have to move 0.75 in. So, the pedal will move:
0.75" * 8 = 6 in I.e. right back where we started.
Pedal pressure could be decreased by increasing the pedal's mechanical advantage, at the obvious expense of having to move the pedal a longer distance, or by using a master cylinder wait a smaller pistion--let's take a look at this using a 0.75 in² piston (which is what McLoed includes in their kit shown above. This means that to create 360 psi will require a force of only 270 lbs be applied to the (smaller) piston:
270 lbs / 0.75 in² = 360 psi
However, to move the 0.75 in³ of fluid needed to move the TOB piston 0.6 in (which it has to to throw out the clutch), the 0.75 in² master cylinder piston would have to move 1.0 in. See what's happening here? Our 8:1 ratio pedal selected above will now only require 270 lbs / 8 = 33.75 lbs of force, but it will have to move 8 in!
But wait, we only want it to move 6 in so it will have to have a 6:1 ratio. Therefore to create the 270 lbs of force needed at the master cylinder piston will require 270 lbs / 6 in = ?
Yup, 45 lbs same as the cable...
OK with that settled let's look at the frictional losses of cable vs. hydraulic actuation. The cable is at a disadvantage in this regard, and at an increasing disadvantage as the operating force increases. However for all practical purposes with most Mustang clutches and modern cable construction (self-lubricating polymer liners and coatings) this disadvantage is negligible.
The only real advantage offer by a hydraulic actuator lies in the flexibility provided by not have to route and align a cable. The hydraulic tubing can turn corners, go over and around the block, headers, steering shafts and etc., without hassle. You could run it to the back bumper and back without measurably affecting pedal effort...
Saturday, April 28, 2012
Rigol DSA815 Spectrum Analyzer...
This is a place holder for my soon to be deilvered Rigol DSA815-TG spectrum analyzer...
• 9 kHz to 1.5 GHz Frequency Range
• Typical -135 dBm Displayed Average Noise Level (DANL)
• -80 dBc/Hz @10 kHz offset Phase Noise
• Total Amplitude Uncertainty <1.5 dB
• 100 Hz Minimum Resolution Bandwidth (RBW)
• EMI Filter & Quasi-Peak Detector Kit (optional)
• VSWR Measurement Kit (optional)
• Standard with Preamplifier and AM/FM Demodulation Function
• Plenty of measurement functions (optional)
• 1.5 GHz Tracking Generator (optional)
• 8 inch (800×480 pixels) high-definition display with clear, vivid,
and easy to use graphical interface
• Complete connectivity with standard interfaces such as LAN,
USB Host, USB Device and GPIB (optional)
• Compact size,light weight (9.4 lbs)
Saturday, January 07, 2012
Digital Torque Apapter
A couple days ago I visited Harbor Freight to buy a 20A
automotive fuse tester, which I did get, however my eye also fell
on this device:
It is their model 68283 Digital Torque Adapter and is one heck of a value for $39.99 (as of 1/30/2012). It uses strain gauge technology to measure deformation of the spindle--which is very much a precision made 1/2" square drive 3 inch extension--under applied torque, and then calculates and displays that torque using the known characteristics of the spindle and magnitude of the distortion. It's claimed accuracy is ±2.0% (it says ±4.0% in the online catalog, but ±2.0% in the manual), however per the calibration sheet and my own tests it is far more accurate than that specification--here is the supplied calibration sheet for my unit, s/n EL00624:
Note: This is intended to be used ONLY with
hand tool input--NOT powered wrenches, torque or otherwise.
I performed my own testing using dead weights of known mass and a 24" 1/2" drive breaker bar (22.75" moment arm), and found the device to be easily within ±0.5% at the points I tested using 20, 40 and 60 pound weights. For example, using the 20 pound weight which with the 22.75" arm should produce 37.92 lb-ft the digital adapter displayed 37.8 lb-ft--an error of -0.31%. With the 40 pound weight (actual torque 75.83 lb-ft) the display was 75.7 lb-ft, -0.18%; or pretty damned close top the 88.5 lb-ft calibration point.
Using the 60 pound weight (113.75 lb-ft actual) the readout was 113.9 for a +0.13% error--I was frankly quite surprised to find that my simple dead weight tests so well correlated to the calibration sheet.
The unit can be set to record the peak torque encountered, or to "trace" (track we Yanks would say) the applied torque (press the P/T button to toggle between the modes). In peak mode it saves the last 50 readings, they may be recalled by pressing the M button. Contrary to the way it is phrased in the manual the last peak torque value is the first displayed when the M button is pressed, an indicator label P01 is displayed briefly then the recorded torque. Pressing the M button again proceeds to P02, etc.
It can display the applied torque in units of lb-ft, kg-m and N-m. The display unit is set by simultaneously pressing the M and P/T keys, repeatedly, until the desired unit is displayed.
A preset torque target, from 29.5 lb-ft to 147.5 lb-ft can be entered into the instrument. Then when torque is first applied the LED will light up in green until 80% of the preset torque is attained when it will turn yellow. When the preset torque is reached the LED will turn red and a piezo "beep" will sound.
I also found in testing that the rated 29.5 to 147.5 lb-ft range is only the range over which the target value can be set. The device will actually measure from 4.0 to 29.0 lb-ft with quite good accuracy. Using a 6.7 pound weight on my 22.75" arm (12.7 lb-ft) the unit displayed 12.5, for an error of -1.6% which is not too shabby.
Perhaps the listed ±2.0% accuracy refers to this full operational range of 4.0 to 147.5 lb-ft?
Because of this level of accuracy, and that as a strain gauge based device such accuracy will be well maintained unless severely overloaded (the manual says that at 125% of full scale the LED will flash red and the alarm will beep), the instrument can be used as a standard against which to calibrate mechanical torque wrenches. Testing my HF 3/8" drive wrench I found it to easily meet its ±4/0% spec, as did my 1/2" drive MAC beam wrench and a very old Snap-On "clicker" I have had for years. When testing a 1/2" drive HF clicker I have used for at least 10 years I found it to be delivering 5 to 10 lb-ft more than its setting across its range. A couple twists of the calibration screw and retesting using the digital device brought it into spec.
Also, finding that it could measure and record peak torque values in the 4 to 29 lb-ft range, I was forced to use it to check the Torque Limiting Spark Plug Socket I reported on in the Fall. At that time I had checked its accuracy using a well-calibrated 1/4" drive and found it to release at 14.2 to 14.8 lb-ft when torque was applied in a rather slow buildup as I was pulling slowly and listening for the "click". This made the dynamic friction of internal ramp and ball more of a factor in its limiting the torque applied to the plug.
Using the digital adapter to record peak torque I was able to better simulate the rotational speed at which a mechanic might use the torque limiting socket. This revealed that with a normal sort of speed the limiter produced 14.2 to 14.5 lb-ft at the plug, and that with a quicker application (still within what a mechanic might actually do) this dropped 13.5 to 13.7 lb-ft. As most, maybe all, plug manufacturers recommend 13 to 15 lb-ft for tapered seat 14 mm plugs this entirely validates the socket's value.
My only negative comment is that the buttons are a bit small for my fat old arthritic fingers, but I can live with that...
Bottom line: I highly recommend the Harbor Freight Digital Torque Adapter, at $40 it is a steal!!!
Monday, October 31, 2011
Torque Limiting Spark Plug SocketI happened upon this tool while assisting a friend with his Beemer M3 and ordered one for testing and evaluation--to minimise the suspense here it is:
What it is, is a spark plug socket with a built-in torque limiter. It works because in the head is a a spring-loaded one-way ramp "ratchet" type device. The input to the tool (a standard 3/8" drive socket recess) is ground to have 4 ramps against which a spring-loaded ball acts. The pre-load on the ball is calibrated such that it climbs and then quite noticeably jumps (releases from) the ramp at a a calibrated input torque--in the case of the 16 mm (5/8") socket typically used with tapered seat plugs this torque setting is 20 Nm (Newton meters), or 14.75 lbft.
Note: This is intended to be used ONLY with hand tool input--NOT powered wrenches, torque or otherwise--I.e. it is not a torque stick.
While a bit higher than the 11-13 lbft recommended by Ford, it happens to be the torque most plug manufacturers specifiy and that I have been using for nearly 5 years on my 2003 Mustang GT and others with no issues--and it beats the crap out of not torquing the plugs at all.
In addition it is a very nice plug socket, long enough to keep the socket from canting in the plug bore. It also has the typical plug socket rubber gripping insert, and a somewhat atypical (meaning well designed) shallow 12-point drive socket to minimise the plug's cocking in the socket itself.
My initial tests proved it to release at 175 to 180 lbin (14.6 to 15.0 lbft) just at it's spec. I then ran it through 450 to 600 rapid cycles¹ using a Milwaukee drill/driver at 600 RPM and found it to continue to cycle at 170 to 178 lbin, 14.2 to 14.8 lbft. Letting it cool back to room temp got single releases in the 174 to 179 lbin (14.5 to 14.9 lbft) range.
Short story is I like it! It is accurate and convenient as heck! I got mine from Norwalk Tools--click here...
¹ - This is the equivalent of torquing a set of 8 plugs, 70 times in a minute or so...
Sunday, October 30, 2011
Dynabeads Inertial Wheel Balancing
These things are amazing and actually do a better job of balancing the wheeles than any machine balance I have ever had-- I will never pay to have a motorcycle tire machine balanced again...
Thursday, August 25, 2011
High Speed Oil Consumption
AN400 K3 crankcase ventilation system:
With the crankshaft whizzing around at 7000+ RPM I can envision a sizable quantity of churned up oil being pulled out via the PCV system. When the weather cools (99.7° here yesterday, 115.9° heat index) I plan on pulling it apart and seeing what I can see...
More about DRP Sliders and Ramp Plates
You can see that the bell on the '07 plate is 6 mm shallower than on the older plate, this does not allow the fixed and movable pulley faces to separate as much. limiting the lower (numerically higher) end of the CVT ratio range. Also visible is that the plate's fingers are 6 mm further inboard than on the older plate. This prevents the fixed and movable pulley faces from moving as close to one another as they can with the pre-'07 plate; limiting the high end of the CVT ratio range.
Here are a coupe of shots of the assembled movable face, with the 18g sliders installed and fully compressed. You can see that the bushing projects 14.65 mm with the 2007 plate, and 15.95 mm with the 2003 plate--this dimension is the farthest apart the pulley faces can be. Therefore with the '07 plate the lowest (numerically highest) attaiable gear ratio is higher than that available with the '03 plate.
On the road I had the same impressions as Ray, and went back to the original ramp plate.
I had about 250 miles on a set of 18g DRP sliders when I played around with the '07 plate, and was a bit dismayed when I opened up the variator and found that the ramp plate's fingers had chewed up the sliders, this despite my having considerably radiused the fingers' hooked ends. Here's a photo of the wear, you can see the flecks of plastic worn from the slider bodies on the seal.
DRP 18g sliders after 250 miles with lightly modified ramp plate:
So, I further ground away and nearly removed the "hook" from the fingers of the stock ramp plate as can be seen in the first photo above. This reduced the slider wear a bunch, here is a photo of them taken 1200 miles after my more aggressive modification of the ramp.
DRP 18g sliders after 1450 miles, 1200 with aggressively modified ramp plate:
This was taken just after opening up the variator. You can see the much improved contact patch, and what remains of the groove worn by the ramp fingers in the first 250 miles.
The ramp finger modification did result in an additional 100 RPM or so at higher speeds, here are the numbers before (top table) and after removing most of the "hook" from the fingers:
I can live with that...
Thursday, July 21, 2011
Quantitative Easing Explained
This is a wonderful explanation of how quantitative easing works--I.e. how we are getting screwed over by the Government's out-of-control spending binge.
Quantitative easing explained -- another MUST watch
Thursday, July 07, 2011
18g DRP Sliders and Speed vs RPM AnalysisI need to get one thing out of the way right up front--WOW!!!
Got 'em yesterday and installed this morning--I put 50 miles on them just now. Assuming the wear is reasonable and I do not experience the "rolling over" of the sliders that has been reported, I have got to place these on my Must Have list of mods. As has been reported by others the rate of acceleration from a stop does feel as though 100cc has been added to the engine, and at high speeds the reduction in engine speed makes things quite enjoyable. I did experienced one very minor downside at higher speeds, more about that below.
On initial take off with moderate to heavy throttle the engine will rev to 6k and as the CVT does it's thing the little beast accelerates quite briskly; noticably faster than with the OEM rollers. Keep the throttle rolled on 'til 55 (actual, 60 indicated) and then roll it back just a bit--the CVT behaves as though it was an automatic overdrive automobile tranny, the revs drop immediately to less than 5k while you settle in at 55mph or so. You can get that added 1k engine speed back by twisting the grip and get some decent 55 to 75 acceleration.
Here are the numbers, the upper table is with the OEM rollers, the lower with the sliders:
As indicated in footnote 1, I did not get a useful observation at 30mph with the sliders. Their cam-like profile makes RPM versus mph quite variable and load dependent at low vehicle speeds--this is a good thing though, making the bike much more controllable and at the same time more responsive at those lower speeds.
The downside I mentioned earlier is that top speed has been affected by the sliders. Because of the 11% higher effective CVT gearing (numerically lower) there is also 11% less torque at the rear wheel to push the bike. On my K3 this brought the usable top speed down from a solid 90 (real, 100 on the "clock") to 82 or so (again real mph). I got it to 85 per the GPS, but it took a good 20 to 25 seconds at WOT to get that last 3mph.
The good new is that it holds a solid 75 at 6650RPM (vs. 7500 with the OEM rollers) with room to spare; I have GIvi windscreen coming in on Tuesday, it will be interesting to see what impact that has.
As others have very well documented the installation process I only clicked a few pics, here's a shot of the rollers as removed:
Something that surprised me is that the working surface is smoother than it was when I pulled them 500 miles or so ago to break the sharp edges on the drive plate.
However after running just 500 miles with the plate fingers radiused 1/64" or so they seem to have smoothed out. Another observation (unscientific using the thumbnail test) is that the synthetic used stock rollers is much softer than the sliders. With a good force I can "catch" my thumbnail on the rollers; no way on the sliders, which I assume to be latest production as they came straight from Union Material.
Here's a closeup of one that I cleaned up, it is much smoother that it was just 500 miles ago:
Before installing the sliders I took the time to hone the plate fingers with a 320m grit aluminum oxide stone--when the 2007 plate I have ordered shows up in a week or so I will get some photos of how the sliders have fared, that should be another 350 miles or so from where I am now.
So there it is, at this point I am VERY pleased with the 18g sliders. Time will of course take it's course and ultimately "tell".
And, that's all I have to say about that...
Update, I just got back from another ride--got about 110 miles on 'em now.
GPS Mount & Engine RPM vs Speed
It's just a twisted up length of 1"x1/8" aluminum flat stock, sprayed with rattle-can "wrinkle" paint. I replaced the cover screws with M4 x 16mm stainless flat head socket caps. The GPS clip mount is one that had a broken inner clamping finger, Garmin had sent me replacement; I just center drilled it and used a M5 button head cap to mount it to the bracket:
Armed with this I set out to reverse engineer the CVT ratios at various vehicle speeds with the clutch locked up. Here is what I found:
Shown here are the tire dimensions (dia = 130 * 0.7 * 2 / 25.4 + 13 = 20.17"), circumference in inches and feet, and the revolutions per mile traveled (interestingly almost exactly 1000 revs/mile). Below that are the K3 AN400 drive ratios, the "primary" being 1:1 as the CVT is driven directly from the crankshaft.
In the table I have calculated the CVT driven sheave speed for each listed vehicle speed; this is the speed in MPH divided by 60 to get miles per minute, this divided by the tire revs/mile to get the tire RPM. The tire RPM is then multiplied by the final and secondary ratios the get the driven sheave RPM.
The engine RPM is that observed on the dash tach at the indicated speed (via GPS), at a steady state speed (with a very slight headwind).
The final column shows the calculated CVT ratio, determined by dividing the engine RPM by the calculated driven sheave RPM--this represents the CVT drive ratio at the selected speed. I found it interesting that there were all very near 1:1, as this is the natural point at which drive efficiency and belt life would be optimised.
One other issue I studied was the function of the cam/spring torque multiplier mechanism of the driven sheave. The cam spiral is such that the movable face moves inward toward the fixed face (pitch increases) when the movable face rotates anti-clockwise relative to the fixed face. You can see in this photo that the movable face has rotated as far as possible anti-clockwise, relative to the fixed face, and therefore the sheave's pitch is at its maximum:
But under what conditions would this happen?
It happens when the belt slips on the fixed face but does not slip on the movable face, which has less rotational resistance unless anti-clockwise to the extreme. So under high loads/hard acceleration, when the belt slips on the fixed driven face, the cam forces the faces together increasing the pitch of the driven sheave and pulling the belt deeper into the drive sheave--against the centrifugal force of the rollers--and increasing the CVT drive ratio--numerically higher, a "lower" gear.
BTW and FWIW, I bent up the bracket using a set of these from Grizzly. Had 'em from years and in addition to sheet metal I have bent 1/4" x 1" aluminum and 1/8" x 1" steel using a heavy duty 5" vise.
Tuesday, May 10, 2011
"calibrated" MAFs and why they suck...
They work by having the output voltage reduced relative to the airflow, either by mucking about with the signal conditioning electronics in the sensor, to report that less air is flowing than really is--or by placing a stock sensor in a larger diameter housing so that sampled flow represents a smaller portion of the total flow.
Both of these procedures result in the MAF "lying" to the PCM about how much air is being ingested by the engine; telling it that less air than is really flowing is coming in.
This is how they allow you to run larger injectors without changing the MAF curve or injector parameters in the tune.
For example, let's say you install 42lb/h injectors in a 2003 GT that cam with 21lb/h units, and install a MAF "calibrated" for the 42lb/h injectors--no changes to the tune are needed as the calibrated MAF lies to the PCM and tells it that 50% less air is flowing.
The PCM says OK and calculates an injector pulse that would create the target AFR based upon 21lb/h injectors (which it believes are still installed). This pulse will be 50% shorter than would be needed with 21lb/h injectors at the real airflow, however since the real injectors are 42lb/h the target AFR is achieved with no change to the tune.
But there is a fly in this ointment...
The PCM also uses incoming air flow, and how much the engine could consume at the current rpm¹, to calculate engine load. The calculated load is then used in nearly every other engine control operation performed by the PCM, in particular ignition timing and fueling.
But as the incoming air flow is incorrect (the "calibrated" MAF is lying to the PCM), the calculated load is also incorrect which is not good. Let's look at just a single example of how this incorrect load can really mess things up.
Here is the Spark Borderline Table from the stock tune for my '03 GT (I have added the 10° base timing to the table values to make things more clear).
This table defines the maximum spark advance to be allowed at various load and rpm combinations. If the PCM calculated advance is higher than the table value the table value will be used, if not the PCM's calculated value is used.
Note that at 40% load, at 5000 rpm, up to 42° advance will be permitted; however that at 80% load only 25° is allowed.
Now imagine that you are really running at 80% load, however your "calibrated" MAF is telling the PCM that 50% less air than is really flowing is coming in. The PCM says "Cool, 40% load, let me pump that timing up to oh, let's say 38°"
Guess what happens to your engine at 80% load and 38° advance? It ain't pretty...
Many other engine control calculations are load based (AFR based on ECT and load being one).
The bottom line is that the only reason, other than to mess with your tuner's mind, to buy a "calibrated" MAF is if you are not planning on tuning your engine properly (or at all) using a modern tuning system. They are legacy kludges that should all be gathered up and tossed into the dustbin of automotive history.
The truth is that any MAF that meets the engine's air flow needs, can be used with any injectors, and any tune--IF you have the MAFs actual transfer function and a tuning system that let's you enter that map into the tune...
Here is an excerpt from the Pro-M website that reveal's the desireability of proper tuning [emphasis aded]:
"As an added bonus, All Pro-M meters are supplied with a transfer function sheet. This is the air mass vs. voltage data for your particular mass air flow meter. This is invaluable information for anyone who desires to have their PCM professionally tuned. It allows the tuner to have the EXACT air mass vs. voltage data for your meter, resulting in a perfectly accurate reading by your PCM. No other method of calibration will provide you with this important information.
Lack of this information will result in a "tune" that is, at best, an educated guess."
So you see, here is the proof that calibrated MAFs are only for those who do not wish to properly tuner their engine...
¹ - This explanation is close enough for this discussion, however it is actually a bit more complex than this.
Thursday, April 21, 2011
SAE 5W-20 Oil Myth
This is presented as a more readable, re-formatting, of SynLube's SAE 5W-20 myth debunker page. Changes are minimal and only to improve structure, grammar, and readability--also the SynLube advertorial content has been omitted.
It is quite accurate in terms of the facts presented, and conclusions drawn.
SAE 5W-20 Motor Oil
Should you use it in your vehicle??
The answer is simple:
You get about 1% better fuel economy, but you get 30% shorter engine life !
The above statement is based on real life experience and is comparison to SAE 5W-30 Motor Oil.
Unfortunately, in order for you to fully understand that short answer, some lengthy explanation is in order...
The SAE (Society of Automotive Engineers) developed, in June 1911, the SAE J300 standard that specifies Engine Oil Viscosity Classification.
Before SAE came up with this scheme to classify oils by their relative viscosities (in plain terms that the motoring public could easily understand) there was no simple way to tell how oil would behave in automotive engine when hot. Back then oils had no W rating, which stands for Winter. Since cars were seldom driven in winter this was not a real problem. The roads were generally impassable and vehicles usually not capable of starting when temperatures approached freezing.
The original SAE viscosity ratings were based on
how quickly a specific quantity of motor oil
flowed through a test orifice when heated to operating temperature (specified as 100°C or 212°F).
The SAE Viscosity Number or Grade according to the initial SAE J300 standard was simply an average time in seconds that tested oil would take to flow through the test apparatus. Since SAE did not want to confuse the public with hundreds of numbers and the simple test yielded different times for different experimenters, it was decided to assign the grades in range steps rather than absolute test values.
Therefore the SAE Viscosity Number
according to the SAE J300 standard was
(and still is) an approximation and NOT an exact measure
- Any oil that took from 5 to 14 seconds to flow would be SAE 10;
- Oil that would take 15 to 24 seconds would be labeled as SAE 20;
- Oil that took 25 to 34 seconds would be SAE 30;
- And so on until SAE 50;
In the original SAE J300 specifications there was no SAE 5 or SAE 60 grade.
The science of Rheology was not well developed at that time, and automotive engineers were neither scientists nor physicists. Therefore it took several years before the SAE J300 staircase was translated from time measurement numbers in a crude instrument into a scientific viscosity values for viscosity expressed in Poise.
By then the J300 SAE Standard was also recognized, but not adapted by API (American Petroleum Institute) and hundreds of oil producers had thousands of cans of oil with SAE numbers already in the market place. So as not to confuse the motorists, who by then gotten used to buying motor oils identified by SAE numbers, the numbering system that by then did not relate to anything comprehensible was maintained.
As far as the author of this article could find the
oldest SAE numbering system for motor oil was as follows:
Flow Test time (seconds)
4.00 ( 2 - 5)
15 to 24
7.45 ( 6 - 8)
25 to 34
10.90 ( 9 - 12)
35 to 44
14.40 (13 - 16)
19.10 (17 - 21)
The last column is not part of the SAE J300 Viscosity Standard, but rather shows the average viscosity values (and the range) of oils that were typically sold within the specific SAE Grade.
The SAE Viscosity Numbers only indicated the
oil’s ability to flow at the test temperature of 100°C;
The SAE Viscosity Number did not in any way
imply suitability for any purpose or quality
or performance of the oil that carried such identification;
- The test was also performed ONLY on FRESH oil, so no durability or stability was ever implied;
During the early days of motoring, motor oils were pure petroleum oil produced with little to no enhancement during processing, nor did motor oils contain any additives. Therefore eventually oil marketers started to label all petroleum oils in the market place with the SAE Viscosity Numbering system numbers, so that consumers could quickly identify what viscosity the oil was when "at engine operating temperature".
This early specification was important for simple reason, oils sourced from different oil fields and different regions had vastly different viscosity index (which at that time was not yet well defined, although recognized by oil people).
Viscosity Index (VI) is nonscientific arbitrary value that simply represents the slope of inverse relationship of oil viscosity to temperature.
All petroleum will flow slowly at room
temperature, and much faster when heated up.
therefore as the temperature is increased viscosity is decreased;
This is known mathematically as inverse
relationship, I.e. if one value goes up (temperature),
then the other goes down (viscosity);
Some oils although they were thick at room temperature would flow as easily as water when hot, yet others that were not as thick at room temperature would not thin out as much. This means that two oils that appeared to have an identical viscosity at room temperature (which was usually the temperature at which the motorist would purchase or pour the oil into the engine), could have totally different viscosity when heated up.
The early automotive engineers even then
recognized the viscosity, as very important quality;
And above all the viscosity when at operating
temperature ("hot") was universally agreed
to be far more important quality than viscosity at ambient temperature;
This was especially important since one oil
sourced from Gulf Coast, could be thick
when cold, yet unable to protect the engine adequately when hot;
By contrast another oil from Pennsylvania, a lot
easier to pour when ambient,
could be just right for automotive engine when hot;
The example of the thick when cold and really thin when hot, was oil with low viscosity index:
VI of 0 – the thick black Gulf Coast aromatic crude would behave like this.
The second example of the not so thick when cold and not as thin when hot, would be the oil with high viscosity index.
VI of 100 (then thought to be the best possible) – the amber oil which came from the oil fields of Pennsylvania and consisting of the paraffin crude that made Pennzoil and Quaker State world famous.
Although viscosity index
was eventually defined by API, it was not of concern to SAE
and still today is not part of any SAE specification.
The actual viscosity at each extreme of engine operation is what automotive engineers agree on as most important specification-- it is this premise that led to the development of multigrade oils.
Over the 70 years that the SAE J300 Standard has existed, a number of shortcomings were discovered and the standard has been amended numerous times.
Although its evolution is of interest, the discussion of its exact detailed history is far beyond the scope of this article, here is in brief what has happened over the 70 years.
SAE 60 grade was added as the need for
thicker oil in aviation and heavy duty engines became apparent.
SAE W grades were added in 1952 as it became
apparent that engines could not be started in colder climatic
conditions with some SAE 30 oils. The W (Winter)
performance was originally defined as viscosity at 0°F or -11.8°C.
SAE 5W and later SAE 0W grades were
added as thinner economy oils needed to be defined.
Additional test specifications for winter
performance were added to W requirements as engines failed
mechanically in cold climates immediately after initial startup, due
to oil starvation.
SAE 15W and SAE 25W grades were added
to further narrow the performance definitions in winter climates.
- In 1970's minimum high temperature high shear specifications were added for performance at 150° C, when it became obvious that engines suffered from excessive wear or even seized at high speed high temperature operation such as long distance interstate driving or towing in hot summer climates.
So the changes to SAE J300 Standard were usually (until very recently) a reaction to fix an existing problem with lubricants that caused engine problems in service. This was generally due either to viscosity breakdown when hot or failure to flow when cold; in either case resulting in catastrophic engine failures.
The last few SAE J300 Standard changes were proactive. They were legislated jointly by the auto and engine manufacturers, as well as the lubricating oil producers, before problems in the field occurred, based on research tests in the laboratories--and therefore done in anticipation of problems.
Many of these specification changes were necessary because today’s cars equipped with electronic fuel injection and electronic ignition will start immediately at much lower temperatures, than vehicles made just a decade ago. Also, because of the proliferation of smaller engines with lower engine oil capacities that produce much more power that put oil under much greater mechanical as well as thermal stress.
The current SAE J300 Engine Oil Viscosity Classification Standard is tabulated below:
Revised DEC 1999 (yes,
this is the current standard as of 4-21-2011)
SAE Viscosity Grade
@ Specified Temp
@ Specified Temp
6,200 @ -35°C
|60,000 @ -40°C||> 3.8|
6,600 @ -30°C
|60,000 @ -35°C||> 3.8|
7,000 @ -25°C
|60,000 @ -30°C||> 4.1|
7,000 @ -20°C
|60,000 @ -25°C||> 5.6|
9,500 @ -15°C
|60,000 @ -20°C||> 5.6|
13,000 @ -10°C
|60,000 @ -15°C||> 9.3|
|> 5.6 < 9.3||
|> 9.3 < 12.5||
|>12.5 < 16.3||
|>12.5 < 16.3||
|>16.3 < 21.9||
|>21.9 < 26.1||
Based on our experience 99.8% of motorists have absolutely no idea what the SAE numbers on motor oil labels really mean. They assume that the simple recommendations in their vehicle owner’s manual are cast in concrete, and that the SAE viscosity of recommended motor oil can not be changed under any circumstances.
The fact that it is quite appropriate to either
increase or decrease the manufacturer's recommended
motor oil viscosity, if it is appropriate for your particular operating conditions and desired engine life.
Here are some real time, as well as laboratory tested, ultimate and unchangeable truths:
The ideal oil viscosity for motor oil used
in conventional piston engine operating at the "normal" engine
operating temperature is equivalent to SAE 30. (In range of 9
cP to 12 cP @ 100°C);
If you use thinner oil (SAE 20 or less),
under normal operating conditions there will be less resistance to
motion due to the lower viscosity, resulting in better fuel economy.
However, this gain in fuel economy does not occur without costs:
- Increase in oil consumption due to lower viscosity (can be offset by better seals);
- Increase in oil consumption due to higher volatility (can be offset by using synthetic oil);
Decrease in engine service life due to
increased boundary wear under some operating conditions
(this will cost more per mile driven or per engine operating hour);
If you use thicker oil (SAE 40 or greater)
under normal operating conditions there will be more resistance to
motion due to the higher viscosity, and therefore worsened fuel
economy. This loss in fuel economy is somewhat compensated for by:
- Decrease in oil consumption due to higher viscosity;
- Decrease in oil consumption due to lower volatility;
Increase in engine service life due to
reduced boundary wear and better separation of parts in relative
If the ambient or operating temperature is
increased from the ideal or normal (70°F/212°F) then the oil viscosity
must be increased to assure same level of protection and lubricating
oil film integrity;
It is not just better, but a must to use SAE 40 oil at 100°F ambient and SAE 50 at 120°F ambient.
If the load is increased such as when
towing, the oil viscosity must also be increased to assure the same
level of protection. (use SAE 50 when towing);
If the engine speed is increased such as
during long distance high speed driving in low ambient temperatures
(so that the bulk oil temperature is not increased) the oil viscosity
could be decreased--that is SAE 20 is preferred to SAE 30 oil (this
however works only for manual transmission vehicles where vehicle
speed and engine speed are proportional and higher RPM can be
maintained by more frequent downshifts if necessary);
If the load is decreased then the oil
viscosity can be decreased
(when an empty tractor/semi-trailer is driven at 70 MPH on Interstate, it is OK to use SAE 30 instead of the SAE 40 that is specified and appropriate when the Tractor is hauling a maximum load at 55 MPH);
The most important factor related to
long-term engine durability and component wear seems to be
the High-Temperature / High-Shear-Rate specification shown in the last column of the SAE J300 Standard;
For SAE 20 oil it is 2.6cP minimum;
For SAE 30 oil it is 2.9cP minimum;
For SAE 40 oil there are two specifications 2.9 cP the same as SAE 30,
and 3.7 cP the same as both SAE 50 and SAE 60 (but why?)
Well the first specification is for light-duty engines (cars that are not expected to last beyond 70,000 to 150,000 miles) and the second for heavy duty engines (that is engines which are expected to last up to 1,000,000 miles). That is why oils which are labeled as HD (Heavy-Duty) must satisfy the second SAE 40 specification of 3.7 cP.
[ed] The lower
viscosity number for multigrade motor oils may be changed (increased
on the lowest ambient temperatures at which you will start the engine. For most of the US and Canada 5W or 10W oils are fine,
however for warmer sections of the country 10W (or even 20W) may provide less wear at startup.
OK the final scoop on SAE 5W-20 and SAE 0W-20 oils:
For many years in the USA automotive manufacturers and importers have been subject to CAFE (Corporate Average Fuel Economy) standards that were passed by US Congress during fuel shortages of the 70's and fear of America running our of gasoline in just a few decades ([ed] which BTW, didn't happen). When enacted these laws forced US auto manufacturers to attempt to match the fuel economy of then popular Japanese Imports.
Car manufacturers get a hefty Federal fines for not meeting the CAFE MPG standards, for every 0.1 MPG by which they fail multiplied by the number of vehicles they sell. That is $5.50 per each 0.1 MPG by which the standard is missed multiplied by the number of vehicles sold in previous model year--which runs annually into millions of dollars.
Success in the car industry is measured ONLY by how many vehicles have been sold in last 10 days.
Therefore every 0.1 MPG by which you can raise fuel economy does matter, and manufacturers are quite willing to sacrifice engine durability. After all, the sooner you wear out your new car, the sooner you will buy another and that is positive impact on the 10 day sales statistics.
You will definitely get better mileage using SAE 5W-20 rather than SAE 5W-30 oil but not by much, optimistic estimates are less than 1%. The bad news is the about 30% reduction in engine life (from 100,000 miles or 10 years to 70,000 miles or 7 years) caused by the thinner oil.
Only manufacturers who have 3 years or 36,000 miles power train warranties currently recommend SAE 5W-20 oil to be used in their 2000 through 2006 model vehicles.
By contrast Mercedes-Benz that offered 4 years or 50,000 miles warranty not only specified SAE 5W-40 motor oil. And in the USA to assure that only that oil grade was used, provided periodic maintenance free to all its customers (free maintenance was offered by Mercedes-Benz from 2000 model years through 2004 model year, it was cancelled on 2005 model cars and SUV's)
All heavy-duty engine manufacturers recommend SAE 40, SAE 15W-40 or SAE 5W-40 oil.
The final choice is yours, you can get 1% better mileage or 30% longer engine life.
If you are leasing a vehicle, then the better mileage parameter is definitely more important as well as cost effective. You just do not care how long will engine last on a car that you will only operate for 24,000 to 36,000 miles. But how many gallons of fuel you will burn will make a difference.
SAE 5W-20motor oil is great–it yields better EPA numbers than SAE 5W-30 oil = better CAFE compliance = lower Federal Fines for not meeting minimal CAFE standards. It typically save the manufacturer about $15.00 per vehicle in CAFE fines;
SAE 5W-20motor oil increases oil consumption–more oil gets used, which is great for oil companies everywhere;
SAE 5W-20motor oil increases mechanical wear, reducing engine life–that way you will buy new car sooner;
Thursday, March 31, 2011
Mustang Rear Axle Gear Guesstimator
This is a thingy I put together a while back, a Rear Axle Ratio Guesstimator.
To use it just get going 40 to 50 mph in 4th gear (3rd for autos) and make note of the selected speed and rpm at that speed; then plug the numbers into the calculator. If you have non-stock rear tires that are of a different outside diameter than stock enter the tire size too.
Here's an example using my GT with 3.73 gears; 50 in 4th is just a bit over 2500 rpm:
It uses a fuzzy math algorithm, meaning that the input values for speed and rpm do not have to be dead on. It has proven to be pretty accurate...
Wednesday, March 02, 2011
Mustang Short Throw Shifters
I have received a number of PMs over the years asking me about short throw shifters, and the MGW shifter in particular--here is my response to the most recent. Aided by my chronic battle with insomnia it got rather verbose so I thought I'd post it for other's benefit.
"I just joined here and have been reading up on this MGW shifter for my car.(04 GT) this is my first stick car so i dont know a good shifter from a bad one.
would you mind explaining what makes the stock one suck and the mgw so much better? all the threads i see about it you seem to chime in with solid info so it seems you know alot about sticks in general.
thanks for any info."
The OEM shifter was designed to (1) minimise NVH (Noise, Vibration, and Harshness), and (2) be as cheap as possible to manufacture.
The first goal, NVH, was heavily (and overly IMHO) influenced by the Mustang V8's popularity and the general "pussification" of the motoring public that resulted in owner complaints regarding stiff and notchy shifting, and interior heat and noise.
To meet goal 1 there are rubber isolators between the shift knob and the business end of the OEM shift lever; resulting in a rubbery, vague, monkey-motion shifting experience--as compared to real sports and racing cars in which the goal to provide precise shifting takes precedence over any other consideration.
Goal 2 was met by fabricating the shifter from crimped together pressed steel plates, with a sloppy fitting pivot ball, and a rather long throw and wimpy centering springs (part of the afore-mentioned pussification).
The OEM shift assembly:
The after market responded with re-engineered versions of the stock design, made of better materials and machined parts, but still basically the same design as the OEM shift assembly--with the fulcrum point moved upward and a shorter lever to reduce the throw.
The Pro-50 (pronounced "pro five-oh") and Steeda Tri-Ax are examples of this genre.
The Steeda Tri-Ax shifter (the Pro-50 is similar but a bit more crudely machined):
MGW entered the market with a completely redesigned unit, sharing only the fact that it let's you shift gears with the OEM; and that the fulcrum has been raised and lever shortened as with the OEM style shifters listed above.
The MGW shifter:
A Word of Caution:
After market shifters, all of them, were designed to first be more precise (less slop and stiffer centering springs) and shorten the shift "throw". NVH considerations were trivial or non-existent.
Therefore all after market shifters will be noisier, notchier¹, hotter, and require more effort to shift gears²--just like real sports/race cars.
There are those who claim that the MGW is notchier and requires more effort as compared to the Pro-50 and Tri-Ax. I have never driven a car with either of those, however as the MGW has the shortest throw of them all it may very well be true.
I have further shortened the throw on mine by taking 3/4" or so off of the lever and the first thing my wife gripes about when she drives my car is how hard it shifts (and the pretty stiff after market clutch)--I never notice it, or the clutch, because that's how high-performance cars are.
If you think you may have a problem with this then you may want to see if you can arrange to drive a car with an after market shifter. As to the MGW, I would not trade mine for anything less than a 2004 Cobra, or maybe a mid-60's Jaguar XKE...
¹ - Notchiness is generated by the transmission's shift rod spring loaded ball and notch detents. A short throw shifter will make the locking action of the detents more noticable because the reduction in mechanical advantage, from the shift knob to the shift rods needed to make the throw shorter, will amplify the force required to overcome the detents' locking action.
² - That a short throw shifter will require more effort to shift is just fundamental mechanical principle. It takes a fixed amount of force and motion to actually move the transmission's shift rods, if you make the lever shorter (than stock, to shorten the "throw") then it will require less motion and more force (than stock) to move the shift rods. There is no escaping this and anyone who tells you otherwise is an ass.
As the range of motion required to move the shift rods is fixed there are only two ways to decrease the "throw" of the operatiing knob. You can raise the fulcrum and lengthen the lower end of the lever, or shorten the upper end of the lever, or a combination of the two as is done by most after market shifters.
I received a followup question asking why a strong centering spring is desireable.
"the only other thing i was wondering about was why you need good centering springs. i would think the less force against you pushing the shifter (into say reverse) the better for ease of shifting."
The strong centering springs work with you to improve shifting by minimising the need for you to "horse" the shift lever into gear, with the effect of a stronger spring being of most benefit in the 2-3 upshift..
Upshifting with a worthwhile centering spring:
- from 1st to 2nd you pull the straight lever back, with some side force to the left to work against the centering spring;
- from 2nd to 3rd just push the lever forward, and let the centering spring move the lever to the center, as you engage 3rd;
- From 3rd to 4th pull straight back;
- 4th to 5th push forward with side force to the right. This can require a bit of manipulation to move the lever through the neutral gate--however the 4-5 shift is not likely to be used in any racing situation.
The 5-4 and 4-3 downshifts benefit from a strong centering spring also, as the spring will force/keep the lever in the 3-4 path, in the center of the pattern.
With a weak or no centering spring the 2-3 upshift and 5-4 downshift would require that you move the lever sideways through the neutral gate, and get it centered on the 3-4 center path, and then move it forward or backward into gear--this is what mis-shifts are made of....
Wednesday, December 08, 2010
Lecroy 9450 FFT Configuration Tool...
Having used a Lecroy 9450A oscilloscope for several years I have yet to find a better all round general purpose digital 'scope in it's price range. $400 to $600 on eBay.
When equipped with the WP02 waveform processing option it can also function as a very competent spectrum analyzer with frequency resolutions ranging from 20μHz to 100MHz, and spans of 0.5mHz to 5GHz, these in a series of possible combinations based upon the timebase setting and selected number of sample points to be processed.
Here's a photo of my 9450A displaying the FM radio band spectrum as available here in Saint Augustine FL:
To gather this spectrum I wanted a 50kHz frequency resolution, and a 200MHz span.
Selecting the FFT frequency resolution is somewhat easy as it is the reciprocal of the timebase setting times 10:
Rearranging this to calculate the timebase setting from the desired resolution we get:
Not too bad...
However calculating the span requires that you know the sampling rate (a factor of timebase setting and RIS¹ or SS² mode), and the maximum number of sample points captured and number of points to be used in the FFT calculations:
While both span and resolution are displayed on the FFT setup screen, configuring the timebase and number of points to get the resolution and span you seek can be a lengthy trial and error process. I wrote the LecroyFFT.exe application presented here to eliminate the need to use the formulae presented above and/or the trial and error process.
It looks like this, here showing the needed time/division and points for the 50kHz resolution and 200MHz span used to capture the FM Band spectrum shown above:
You will also see that the capture characteristics for the needed timebase setting are displayed at the bottom of the dialog. Shown are the seconds/division, the RIS samples/second and record length, and the SS samples/second and record length.
To use the application just select the desired resolution from the list at the left, this will cause the needed timebase setting to be displayed (2μs above) and load the span list with the spans available for that timebase setting.
Next select the desired span (and RIS mode if desired and available--more about this below), the required number of points to be used in the FFT calculation will be displayed (8000 above).
That's it, now just set the indicated time/division on the 'scope, and set the required number of calculation points in the FFT configuration menu.
RIS mode is required for timebase settings of 1ns to 5ns, available for settings of 10ns to 5μs, and not available from 10μs to 5000s. The application will show messages indicating the availability of RIS mode.
There is only one application configuration option, so to keep things simple I just included it of the About dialog:
Checking the Confirm Exit box will cause the application to pop-up a dialog when you close it (via the standard Windows Close button). The dialog will ask if you wish to close or minimise the application, I added this because I found myself closing the app when all I wanted to do was minimise it. Some find this sort of thing annoying so I made it configurable.
You can download the application in a Windows installation package by clicking here.
¹ - RIS = Random Interleaved Sampling capture mode
² - SS = Single Shot capture mode
Sunday, August 15, 2010
Steve Wynn takes on Washington...
This is Steve Wynn, a casino resort/real-estate developer who has been credited with spearheading the dramatic resurgence and expansion of the Las Vegas Strip.
Here he talks about the Fall of America--listen to this fellow he is dead-on!
Steve Wynn takes on Washington -- May 29, 2010 -- a MUST watch
Saturday, August 07, 2010
I must start by stating that this write-up on gasoline octane ratings isn't my work, it’s something I found on the Internet in a news group. I have edited it to correct spelling and grammar, and improve readability however the informational content remains unchanged. I am hoping this information will be useful to others as it was to me. Despite its being perhaps 20 years old the theory hasn't changed.
The octane number of a gasoline IS NOT a measure of its hotness or coolness in the burning process, nor is it a measure of how powerful it is—it is simply a measure of how good the gasoline is at resisting detonation (knocking/pinging).
The internal combustion engine is, in the most simple of terms, a self-powered air/fuel pump.
It drives itself by creating pressure to push on a piston connected to a crankshaft via a connecting rod. The pressure is created by heating a cylinder full of air and fuel; and then igniting it with a spark causing the mixture to release energy and expand. The higher the pressure inside the cylinder, the more push there will be on the pistons and the higher the engine’s power output will be.
One goal of internal combustion engine engineers is to get the highest possible pressure without creating uncontrolled burning or even an explosion of the fuel mixture.
Detonation occurs after the fuel is ignited by the spark plug, but before the flame front has finished moving across the cylinder to burn all the fuel/air mixture; and should not be confused it with pre-ignition, which occurs when the fuel is ignited before the spark occurs. The reason detonation occurs relates to the nature of gasoline, which is a mixture of different hydrocarbon molecules; some of these molecules decompose (burn) more easily than others when heated under pressure.
As the fuel/air mixture is ignited by the spark plug, the flame front begins moving across the cylinder from the point of ignition. When detonation occurs the increasing the temperature and pressure of the remaining air/fuel mixture and causing it to decompose before the flame front reaches it. If this decomposition produces auto-ignition compounds (compounds that can and will start burning without a spark) the result is an uncontrolled overly-rapid burning of the remaining fuel. This uncontrolled burning generates an opposing pressure wave (relative to the intentionally triggered wave) in the cylinder and the opposing pressure wave and results in the piston getting a hammer blow instead of a steady push. The clicking and pinging (pinking to those on the other side of the pond) noises are the sounds of detonation.
These hammer blows of detonation can quickly destroy an engine.
There are three main sources of heat inside the cylinder which contribute to the decomposition of the fuel:
- Residual heat in the heads, cylinders and pistons;
- Heat produced by the ignition of the fuel itself (this depends on the nature of the fuel, and on the fuel/air mixture; rich mixtures burn a little cooler, lean mixtures burn hotter);
- Heat of compression before the spark. (compression of a gas raises its temperature, which we want to happen. However if the sum of residual heat, heat from combustion, and heat from compression exceeds the fuel’s decomposition limits then things go BOOM....
Using Higher Octane Fuels:
The benefit of higher octane fuels is that they are better at controlling their decomposition into auto-ignition compounds than lower octane fuels. They do this in several ways by interfering with and reducing the actual decomposition; or by chemically reacting with the decomposing gasoline so less auto-ignition compounds are formed. Octane numbers came about as a result of research carried out in the 1920s and 30s by Sir Harry Ricardo (The Internal Combustion Engine; 1925/35) and Kettering (of Kettering ignition system fame).
When Ricardo was asked to develop an engine for a British WW1 tank in 1916, he used a previously developed and quite ingenious variable compression test engine in his research.
- (Incidentally, this engine was extremely innovative for it's day, and was utterly reliable - so it also got used as a stationary generator engine by the British army for their field stations all over France, and by the British Navy for it's patrol boats, as well as about 12,000 tanks. The Army and Navy loved it because it would run on just about any liquid fuel—it would even run on a kerosene/gasoline mix if that was all they had! It was just as happy, but gave no extra power, on high grade aviation gasoline.)
Ricardo discovered that iso-octane (2,2,4 trimethylpentane) had a very high knock resistance, but that n-heptane (dipropyl methane) had a very poor knock resistance, and because these two compounds are very similar in other respects, they made a useful comparison point for gasoline. Ricardo assigned iso-octane to represent an anti-knock value of 100 and heptane to a value of 0.
So, the octane rating of any given fuel is based upon its anti-knock properties as compared to a mixture of iso-octane and heptane with the same anti-knock characteristics. I.e. a 91 Octane rating is equivalent to a mixture containing 91% iso-octane and 9% heptane.
In the late 1920s it was discovered that certain compounds of lead enhanced the anti-detonation characteristics of internal combustion engine fuels—gasolines could be doped with tetra-ethyl or tetra-methyl lead to enhance their octane numbers. This revolution in fuel design led to engines that could operate at higher compressions for better efficiency and increased power.
Another useful feature of lead in gasoline was that the burned lead products coated the exhaust valve seating area, greatly reducing a wear problem called valve seat recession (VSR) which results from the exhaust valve “eating” it's way into the head. With the less advanced softer cast iron heads of the day, this was a real bonus. VSR is not a significant problem with newer engines as they typically have hardened valve seat inserts.
Gasoline which is high in aromatics (sweet smelling hydrocarbon compounds) has a high natural octane rating, and so needs fewer additives to increase the octane rating—unfortunately however the aromatic compounds are also those most responsible for atmospheric pollution, so these compounds have been reduced in gasoline in many countries. This creates another dilemma, how to increase the octane rating without lead additives, and with reduced aromatic compounds in the fuel.
A number of other chemical compounds called oxygenates (compounds infused with oxygen) have been developed to enhance the natural octane number of gasoline. The most common one used is Methyl Tertiary Butyl Ether (MTBE), some other compounds include TAME, ETBE, Methyl Alcohol and Ethyl Alcohol (Gasohol). But since MTBE and the other oxygenates contain oxygen, cars using oxygenates fuels burn more fuel because there is less “fuel” in the fuel and this increases pollution anyway (Cleaner Burning Gasoline California EPA). California and other states have banned MBTE as an environmental hazard; ethanol is often used as a replacement.
Ricardo used the research method of measuring the octane number using a constant speed (1500 rpm) engine in laboratory conditions—this is the RON or Research Octane Number. The other method is called MON (the Motor Octane Number), which is measured using a harsher test regimen, more closely related to road conditions. MON is usually lower than RON. Often you may see the octane rating quoted as (R+M)/2. This means an average of the two methods was used to rate the fuel’s anti-knock characteristics—this method is often called pump octane in the US.
The bottom line is that using a higher octane gasoline than that for which an engine was designed and tuned WILL NOT increase its performance—all that is necessary is the octane rating needed to eliminate detonation, and you will find that the manufacturer’s recommended grade of fuel has been selected to exceed that need. There are of course exceptions to those recommendations, generally the result of one or more of the following conditions:
- Using higher octane fuel and retuning the engine to take advantage of same can increase power output, but only up to a point. Spark timing can be advanced on most modern engines that were originally tuned for 87 octane fuel by about 2° per unit increase in the octane—however when spark advance reaches the point that the peak cylinder pressure occurs to close after TDC power output will decline.
- At that point using a yet higher octane fuel will accomplish nothing.
- Extremely high operating temperatures resulting from constant high output demands and/or extreme ambient temperature;
- Increased compression ratio resulting from carbon build-up in the combustion chamber or piston crowns;
- Higher compression pressures brought about by forced induction (turbo or super charging) modifications. If the air/fuel mixture is introduced into the engine at higher than atmospheric pressure (which can never happen with a “normally aspirated” engine) then more gets in, at higher initial pressure
In conclusion, a fuel’s octane rating is ONLY a measure of that fuel's ability to CONTROL the burning process and to prevent detonation—it is not a result of its burning “hotter” or “colder”, or of its ability to produce more power, and is nearly entirely determined by the compression ratio of the engine in question.
Higher compression engines must run high octane fuel, and lower compression designs are able to run lower octane fuel. (that’s a “period”, as in the end of the story…)
 Higher compression produces higher final pressures after the fuel is burned, which produces more power. The heat generated by compression is easy to adjust in the design of an engine, as it is directly related to and engine’s compression ratio. Therefore, compression ratio directly links an engine design to the grade of fuel it will require.
 The British War Ministry had traditionally purchased fuel specified by specific gravity, Ricardo estimated some years later that it had an octane rating of about 45—his tank engine was limited to a compression ratio of about 3.5:1 to cope with this poor fuel!
 Carbureted engines do not adjust the air/fuel ratio on-the-run as do modern electronically controlled fuel-injected engines. They will run lean on oxygenated and ethanol fuels and their carburetors must be re-jetted to recalibrate the air/fuel ratio.
 Ethanol produces a whole new set of issues however, pure ethanol contains some 34% less energy than conventional gasoline (about 30% less than oxygenated gasolines) which means that an engine must burn more of it for equal power output—which means fuel economy is reduced. At mixtures of up to 10% ethanol this reduction is only 3% or so, however with E85 (85% ethanol) fuel the reduction is 27%.
Monday, August 02, 2010
FuelMaxx Fuel Maximizer Control Module (21st Century Snake Oil)
In a recent posting on the Mustang Forums a fellow asked about the FuelMaxx "performance chips" being sold on eBay, he was excited by the prospect of adding 30 HP and 4 MPG with just a $22 investment and was seeking advice from his fellow forum members as to the value of the unit--to their distinct credit the forum responded with a unanimous and overwhelming combination of LOL, OMG, and a couple of WTFs?
Having not debunked anything like this in more that a few years I said "What he heck?" and ordered one of the "Maximizer Modules". My first reaction upon seeing the eBay posting had been that is was one of what was once, in the early days of EFI, known as a "resistor trick"--upon receiving and analyzing the "module" I find no disappointment in my initial assessment.
The resistor trick worked by inserting a resistor in series with the intake air temperature (IAT) sensor, which made its apparent resistance higher, which in turn tricked the Engine Control Unit (ECU) into believing the intake air was cooler that it really was. This caused the ECU to add fuel and timing--which in the days of auto makers' solution to the EPA fuel economy ratings being to make the engine run lean--actually could add some horsepower. It also generally drove fuel economy down.
The FuelMaxx applies the resistor in parallel which confused me at first, more about this below.
Inside the FuelMaxx (a virtual view for now):
The module is a rather small plastic "project" box, approximately 2" x 1-1/2" x 7/8", it weighs a couple ounces; mostly because of the potting compound used to protect the "sensitive components" of the "internal electronics" from prying eyes--it is rather effective at that. The box has two wires of 18 gauge or so; one red one black; and a small bit of double sided tape on the back so that it might be "mounted" in the engine compartment. It is provided with a short bit of split wire loom, two 3M wire taps, and a nylon wire tie.
So that those with only modest interest don't have to read this whole entry, here's the bottom line.
The FuelMaxx device is a 3¢ 22kΩ resistor in a 15¢ plastic project box, the potting material probably cost more than the resistor, box, and wire.
Per the included instructions it is installed in parallel with the Intake Air Temperature (IAT) sensor. The IAT sensor is a negative temperature coefficient (NTC) thermistor, meaning that as the air temperature increases the electrical resistance of the IAT decreases. At 68°F it's resistance is 37.30kΩ and at 86°F it is 24.27kΩ.
By wiring the FuelMaxx 22kΩ resistor in parallel with the IAT its effective resistance is reduced as shown in the following table, and according to this formula:
The reduction in effective resistance makes the PCM (Powertrain Control Module) believe the incoming air is warmer than it really is, which as I said above confused me at first. However it came to me that by telling the PCM the intake air is warmer it will inject less fuel. While the adaptive learning system will counteract this to some extent in closed-loop mode, this could perhaps support the increased fuel economy claim (I said "perhaps", it [the FuelMaxx] is still a rip-off and a kludge).
Thinking it through further I realised that most modern engines run a bit rich in open-loop mode. Emissions standards do not apply to WOT operation, and in order to run the donkey-piss 87 octane fuel the Feds have imposed upon us having the mix rich provides a hedge against detonation. Most (maybe all) "canned" tunes for the Mustangs lean out the commanded AFR in the Stabilised Open Loop Fuel Table. This could (perhaps) support their increased performance claim--however +30HP is a crock.
Here's what the FuelMaxx looks like:
Here's what the opened up backside looks like:
While I have not yet taken on the task of releasing the magic smoke from it's confines, I first performed simple resistance and capacitance tests.
The device's resistance and capacitance are 21.83kΩ and 0.000nF, respectively:
Both of which fully convinced me that what's inside is no more than a 22kΩ resistor. Nonetheless to go a step further, and assure the faithful that they did indeed get screwed, I performed a network analysis bode plot to determine the device's transfer function.
A bode plot is produced by passing an AC signal though the device under test (DUT) and examining the relationships (generally amplitude and phase shift) of the input and output signals.
To perform this test I used the network analysis capability of Velleman's PCSU1000 oscilloscope, and their PCGU1000 function generator. These are both USB connected PC-based instruments, that can be fully controlled by the host computer. When paired up and controlled by Velleman's PCLab2000 software it is possible to perform a completely automated network analysis--this capability is WFC for a couple of instruments that cost less than $600 for the pair!
This is the instrument and DUT (Device Under Test, aka FuelMaxx) configuration:
Here's what I found when scanning the device's response form 10Hz to 10kHz:
The blue trace is the FuelMaxx's frequency response, that it is a flat line indicates a purely resistive load. No other electrical component would display a straight line in this test.
The brown trace is that of a 1.9¢ (I buy in bulk) 22kΩ resistor.
The green trace is the that of a simple RC (Resistor/Capacitor) filter using the 22kΩ resistor and a 0.005μF capacitor. I did this to illustrate that if there were any other electronic components inside of this "thing" the bode plot would not be a straight line.
Note: The very slight amplitude drop and phase shift at the right end of the FuelMaxx and resistor plots are due to stray capacitance in the micro-clip test leads I used for this "quicky" test--you can see that both the FuelMaxx and 22k resistor have the same curves. The shift caused by just adding the 0.005μF cap is far greater.
I plan on breaking apart the potting to see if I can get a view of what's in there, however this will likely be a somewhat destructive process--we'll see what we can see...
Wednesday, July 21, 2010
Delta Force Tuning - Special Forces Tuning system
The Delta Force Tuning Special Forces (SF) tuning system is intended as competition for the various hand held tuners offered by other manufacturers; and it does that quite nicely by offering much more flexibility, the ability to have five tunes loaded into the interface, and to tune two vehicles at any point in time--with no limitations as to how many times you can change vehicles.
There are three Windows® based applications that make up the system:
- the MultiLoader utility, used to download the stock tune and upload custom tunes to your car;
- the Special Forces tune editor, used to create and edit custom tunes;
the Bullet utility, seldom used but which allows you to
purchase and add "bullets",
to allow tuing more than two vehicles;
I do not intend this to be, nor is it, comprehensive documentation of the SF system. It is rather an overview of what Special Forces is and what it can do; with the primary focus on the Special Forces editor. SF is a great entry level tuning system, far superior to any of the hand held systems in its price range, however it is important to understand that it is just that--an entry level system. Please read the Final Comments section below for more.
Special Forces, unlike the hand helds, creates complete customised tunes based upon your responses to a series of questions and selections related to your vehicle's configuration. Your input is processed and applied to your car's stock tune to create a base custom tune, made with known (and safe) performance improvements.
The base tune settings (most, not all, see my SFScrape.exe application for more about this) are saved to an encrypted file that can be reloaded into the SF editor and fine tuned. Fine tuning consists of applying modifiers to the timing and fueling settings.
Any number of base and "fine tuned" tunes may be created, as stated above any five of these may be loaded/reloaded/overwritten into the interface and be available for flashing to the PCM.
How does it work?
This is the initial screen, you elect to either open an exisitng, or create a new, tune;
Here I have elected to create a new tune, and have entered the
Computer Box Code;
The box code is obtained from your stock tune, which when downloaded from your car into the DF interface will be saved to a folder named Original Files, located in the Delta Force Tuning data folder. The filename will be in the format sssss.bbbb.pcm where sssss is the tune's strategy code and bbbb is the box code.
You would make the other selections according to your car's configuration.
The next screen let's you describe your fuel system;
The selections are self explanatory, with many/most common values available in the drop down lists.
Next are MAF related selections, again most common devices will be
available from the drop-downs;
Now you will define your exhaust and ignition configuration;
And in the last a number of general modifications and settings;
Clicking [End] will open a dialog asking that you provide a name
for the newly created base tune;
Enter a name for the tune and click [Save], SF will let you know the tune has been saved, and exit.
That's it your new custom base tune has been created!
Once a base tune has been defined you can re-open it for fine tuning.
To do so, launch Special Forces and elect to Load a Saved Tuning File
from the initial screen (see above), a typical Windows file open dialog
will be opened;
Select the tune you wish to edit and click [Open].
The Tell Us About the Automobile dialog, and all the others shown
above will be availablle, and in addition you will have access to the
fine tuning page;
Here you can select modifying values for fueling and ignition timing.
When you have made these selections click [End], you will be
asked for a name for the tune--use a different name that describes the
That's it, click [Save] and you will have created and stored a fully customised tune. The next steps would be to use the MultiLoader utility to save the tune to the USB connected OBD2 interface, and then connect the interface to your car's OBD2 port and flash the tune. I am not going to document that here as full instructions are included in the package you will receive.
What about automatic transmissions, forced induction, and nitrous?
Glad you asked...
The options for automatic transmission tuning are comprehensive;
If you are running forced induction or nitrous (one or the other, not
both) these options will be available;
Special Forces excels at what it was designed to do, this being a superior alternative to the hand held systems in its price range, however like them it is also an entry level system. What this means is that it can provide good tunes for what would be considered "bolt-on" engines, with that classification including packaged supercharger, turbo, and nitrous kits, assembled by the many reputable and knowledgable after market performance vendors.
It is NOT suitable for heavily modified "built" engines, custom assembled power adders using non-standard or unmatched components, or for serious high performance tuning. Its "big brother" Delta Force Commando is.
So if you have a heavily modifed engine, or are one of those like myself that wants complete access and control of your engine's tuning, I strongly recommend that you skip over Special Forces and purchase the Commando system right up front.
Commando comes with the Special Forces editor so that you can easily create tweaked initial tunes and then load those tunes into Commando for full access to every one of the tune file's scalar values, tables, and functions.
Commando has no competition in its price range.