RE: My PCM tuning with PCMforLess.com - Process and Results
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 9:13:19 AM
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HummerMike
Posts: 376
Joined: 8/8/2006
From: Crown Point, IN
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Those are some pretty cool numbers. I'm very impressed.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 10:27:11 AM
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Ghostrider
Posts: 542
Joined: 9/18/2006
Status: offline
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quote:
ORIGINAL: ChevyHighPerformance
quote:
ORIGINAL: Dennis
God, Numbers, give me numbers..I love this kinda talk...gives me goose bumps 
Anyway, excellent report and very enlighening...Just curious, How did you measure the fuel consumption actually? Was it a mathimatical result, based on MAF-Airflow and O2 emissions readings?...I assume you were plugged in with a lap-top while perforing these road tests...This is all very intriguing as to your test bed..Cool beans man!
I didn't measure the gas flow directly. It was a mathematical calculation. I had to do some post processing of the data to get the posted numbers.
OBD2 stuff!! I wrote a few computer applications for this over the summer!
Did you use the stoichiometric MAF/14.7? You actually dont need data from the O2 sensors since the point of a computer controlled fuel system is to make sure 14.7 = A/F where A = air volume from MAF and F = fuel volume. The engine will automatically use the O2 data to control rich and lean conditions..all you care about for fuel flow is the MAF sensor. But the O2 sensors do make a difference. They need to be heated to 600 degrees in order to work so thats why when you start up your engine when its cold it sounds like its got a supercharger for a little bit because its bypassing the O2 data and running very rich until those sensors get heated up. The trick here that you showed is how the playing with long and short term fuel trim levels..aka cruise and acceleration trim rates. This is also why you should do all engine work and then get a PCM tune because lets say you put a K&N and exhaust system on, and get a HP boost from it. The extra HP will change your fuel usage and the engine will think it is outta whack. It will start playing with the fuel trim levels to basically de-tune itself until it sees the numbers it expects to see.
But you did a nice experiment with your numbers to actually show what these little computers are doing in our engines!!
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 11:26:16 AM
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ChevyHighPerformance
Posts: 159
Joined: 7/5/2006
Status: offline
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quote:
ORIGINAL: Ghostrider
quote:
ORIGINAL: ChevyHighPerformance
quote:
ORIGINAL: Dennis
God, Numbers, give me numbers..I love this kinda talk...gives me goose bumps
Anyway, excellent report and very enlighening...Just curious, How did you measure the fuel consumption actually? Was it a mathimatical result, based on MAF-Airflow and O2 emissions readings?...I assume you were plugged in with a lap-top while perforing these road tests...This is all very intriguing as to your test bed..Cool beans man!
I didn't measure the gas flow directly. It was a mathematical calculation. I had to do some post processing of the data to get the posted numbers.
OBD2 stuff!! I wrote a few computer applications for this over the summer!
Did you use the stoichiometric MAF/14.7? You actually dont need data from the O2 sensors since the point of a computer controlled fuel system is to make sure 14.7 = A/F where A = air volume from MAF and F = fuel volume. The engine will automatically use the O2 data to control rich and lean conditions..all you care about for fuel flow is the MAF sensor. But the O2 sensors do make a difference. They need to be heated to 600 degrees in order to work so thats why when you start up your engine when its cold it sounds like its got a supercharger for a little bit because its bypassing the O2 data and running very rich until those sensors get heated up. The trick here that you showed is how the playing with long and short term fuel trim levels..aka cruise and acceleration trim rates. This is also why you should do all engine work and then get a PCM tune because lets say you put a K&N and exhaust system on, and get a HP boost from it. The extra HP will change your fuel usage and the engine will think it is outta whack. It will start playing with the fuel trim levels to basically de-tune itself until it sees the numbers it expects to see.
But you did a nice experiment with your numbers to actually show what these little computers are doing in our engines!!
Yes and no. I measured fuel consumption in two ways. One was with the MAF and you want to monitor total airflow g/s or lb/min (not cylinder air mass even though they have the same units). In order to do this, all the Ltrims need to be learned to make sure you are running at 14.7:1 A/F and the MAF needs calibrated (it can't have and inaccurate peaks or valleys in its response). For relative fuel testing you don't need to divide by 14.7 because it's just relative, but if you want the absolute consumption you need the 14.7.
The another way I used is based on fuel pressure, MAP (manifold absolute pressure), and injector pulse width. The fuel presure and MAP give you the delta pressure across the injectors that let you calculate the flow based on injector on time.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 11:51:34 AM
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Ghostrider
Posts: 542
Joined: 9/18/2006
Status: offline
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quote:
ORIGINAL: ChevyHighPerformance
The another way I used is based on fuel pressure, MAP (manifold absolute pressure), and injector pulse width. The fuel presure and MAP give you the delta pressure across the injectors that let you calculate the flow based on injector on time.
Interesting...did you get fuel pressure from the OBD port? I could never seem to get the code right for it and figured the sensor wasnt on the network.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 2:35:11 PM
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ChevyHighPerformance
Posts: 159
Joined: 7/5/2006
Status: offline
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quote:
ORIGINAL: Ghostrider
quote:
ORIGINAL: ChevyHighPerformance
The another way I used is based on fuel pressure, MAP (manifold absolute pressure), and injector pulse width. The fuel presure and MAP give you the delta pressure across the injectors that let you calculate the flow based on injector on time.
Interesting...did you get fuel pressure from the OBD port? I could never seem to get the code right for it and figured the sensor wasnt on the network.
Nope.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 5:13:55 PM
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lotus4s
Posts: 48
Joined: 8/21/2006
Status: offline
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quote:
ORIGINAL: Alvin@pcmforless.com
We've noticed with some of our customers that it takes a few weeks to see an increase in gas mileage. Not because of the tune, but because they have been getting right foot happy with the new power
That is a distinct possiblility....
_____________________________
06 H3 Superior Blue, lux/adventure, sunroof, oem ucp & rock rails, 35" Cooper STT's, DOI winch bumper, gobi stealth rack and PIAA 1500xt's, dvd
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/14/2006 6:00:31 PM
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HummerGuy
Posts: 6679
Status: offline
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I received mine today and installed it. Instead of taking an hour like last time (because it was the first time), it only took me 15 minutes to swap them out. Piece of cake! It started right up without a problem. I'm running 93 octane and that's what it's tuned for.
It will be interesting to see what the manual transmission results are. I'm going to read all this technical data you guys wrote about and ask some questions, because I really want to learn about this stuff.
I'm taking about 100 mile trip tonight, so that should be plenty to feel if there is a difference. I will post later (LATE) tonight and let you guys know.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/15/2006 12:03:16 AM
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Linus Gump
Posts: 960
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In one of my more technical engine theory classes I learned that power is equal to pressure in the cylinder (atmospheric pressure at WOT on a non pressurised engine) times the length of stroke times the area of the piston times the number of times per minute, or number of cylinders; or simply: POWER=PLAN. Also there is a specific fuel consumption for a given power output within a specific amount of time, figured: SFC= lbs. fuel/bhp/hour, where SFC is the specific fuel consumption, which equals the number of pounds of fuel consumed divided by the brake horse power divided by one hour. It would seem to me that all you would need to do is determine the difference in manifold pressure from an idle to WOT. Then, based on standard atmospheric conditions of 59F deg and a barrometric pressure of 29.92" hg @ sea level, you could determine any power setting and fuel consumption between the minimum manifold pressure at an idle all the way to maximum manifold pressure at max RPM.
In a basic aerodynamics class I learned about coefficient of drag. Coefficientof drag is equal to drag divided by dynamic pressure times area, or: Cd=D/q*A.
So it would be possible to find the coefficient of drag for the vehicle, and determine how much power is required to maintain a given speed. Then take this drag information and determine what power setting, or throttle position, would be required to maintain it, or to accelerate to it. When drag equals the power being produced, then you have a constant speed. Any more power than this will be used for acceleration. Using this power requirement as the BHP in the fuel consumption formula and figuring the lbs fuel used to produce that power from the air/fuel ratio will give you the specific fuel consumption for that power setting, and thus be able to figure the fuel consumption for that speed.
My question is, why couldn't you figure all of this stuff at your desk instead of driving around and trying different things to determine the best comprimise between fuel economy and power? Wouldn't it be chaper? I know nothing about programming a computer, so maybe I am missing something here. I do realise that on paper things would be figured for the specific conditions given, such as the standard atmosphere, but shouldn't the basic program of the PCM compensate for the differences of the actual conditions compared to the standard?
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/15/2006 11:39:09 AM
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Ghostrider
Posts: 542
Joined: 9/18/2006
Status: offline
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quote:
ORIGINAL: Linus Gump
In one of my more technical engine theory classes I learned that power is equal to pressure in the cylinder (atmospheric pressure at WOT on a non pressurised engine) times the length of stroke times the area of the piston times the number of times per minute, or number of cylinders; or simply: POWER=PLAN. Also there is a specific fuel consumption for a given power output within a specific amount of time, figured: SFC= lbs. fuel/bhp/hour, where SFC is the specific fuel consumption, which equals the number of pounds of fuel consumed divided by the brake horse power divided by one hour. It would seem to me that all you would need to do is determine the difference in manifold pressure from an idle to WOT. Then, based on standard atmospheric conditions of 59F deg and a barrometric pressure of 29.92" hg @ sea level, you could determine any power setting and fuel consumption between the minimum manifold pressure at an idle all the way to maximum manifold pressure at max RPM.
In a basic aerodynamics class I learned about coefficient of drag. Coefficientof drag is equal to drag divided by dynamic pressure times area, or: Cd=D/q*A.
So it would be possible to find the coefficient of drag for the vehicle, and determine how much power is required to maintain a given speed. Then take this drag information and determine what power setting, or throttle position, would be required to maintain it, or to accelerate to it. When drag equals the power being produced, then you have a constant speed. Any more power than this will be used for acceleration. Using this power requirement as the BHP in the fuel consumption formula and figuring the lbs fuel used to produce that power from the air/fuel ratio will give you the specific fuel consumption for that power setting, and thus be able to figure the fuel consumption for that speed.
My question is, why couldn't you figure all of this stuff at your desk instead of driving around and trying different things to determine the best comprimise between fuel economy and power? Wouldn't it be chaper? I know nothing about programming a computer, so maybe I am missing something here. I do realise that on paper things would be figured for the specific conditions given, such as the standard atmosphere, but shouldn't the basic program of the PCM compensate for the differences of the actual conditions compared to the standard?
Im a programmer but I work on a solar powered race car for my university so I know a little about aerodynamics since we do a cross the country race using the power of a hair dryer at 70mph. The problem in calculating these values is that getting a good front area calculation is difficult from the angles and requires loooots of fluid dynamics to find the coefficient of drag and then apply that to an accurate reading of the cross section area. OR..you google it!
To calculate aero loss, F = .5*(Cd*A)*r*V^2
Cd = Coefficient of drag
A = cross section area of front of car or wind profile
r = rho = density of air
v = velocity (ft/sec)
for the H3..Google (Track & Driver Magazine) says
A*Cd = 16.8 ft² (1.56 m²)
To calculate rho, air is 79% nitrogen and 21% oxygen. nitrogens molecular weight is 28 and oxygens is 32. so
r = ((.79*28)+(.21*32))/22.4(molecular weight volume)
r = 28.84g/22.4l = 1.29g/l
Converting this to pounds per cubic foot,
r = .0801
So...
F = .5*16.8*.0801*v² ² (in ft/sec)
Cleaning this up to make it for MPH, you're left with..
F = .986832*V² (in mph)
Which gives you a unit of pound mass..which isnt even a "real" unit so lets make it HP loss for better understanding...
F = (.986832/32.1)*V² in pounds of force..much better but not HP.
P = ((.986832/32.1)/550)*(22/15)*V^3
And theres your HP loss formula..just plug in V in mph and do the math. (You can copy that formula into google with your speed in V and it will compute it for you.
h
< Message edited by Ghostrider -- 10/15/2006 11:41:02 AM >
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/15/2006 12:06:57 PM
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ChevyHighPerformance
Posts: 159
Joined: 7/5/2006
Status: offline
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"It would seem to me that all you would need to do is determine the difference in manifold pressure from an idle to WOT. Then, based on standard atmospheric conditions of 59F deg and a barrometric pressure of 29.92" hg @ sea level, you could determine any power setting and fuel consumption between the minimum manifold pressure at an idle all the way to maximum manifold pressure at max RPM."
You can get the manifold pressure from the MAP sensor.
"In a basic aerodynamics class I learned about coefficient of drag. Coefficientof drag is equal to drag divided by dynamic pressure times area, or: Cd=D/q*A.
So it would be possible to find the coefficient of drag for the vehicle, and determine how much power is required to maintain a given speed. Then take this drag information and determine what power setting, or throttle position, would be required to maintain it, or to accelerate to it. When drag equals the power being produced, then you have a constant speed. Any more power than this will be used for acceleration. Using this power requirement as the BHP in the fuel consumption formula and figuring the lbs fuel used to produce that power from the air/fuel ratio will give you the specific fuel consumption for that power setting, and thus be able to figure the fuel consumption for that speed."
You can measure CdA with a simple test or you can find it here in a Car and Driver article (http://www.caranddriver.com/roadtests/9742/hummer-h3-page4.html) (Drag area, Cd (0.51) x frontal area (32.9 sq ft): 16.8 sq ft)
"My question is, why couldn't you figure all of this stuff at your desk instead of driving around and trying different things to determine the best comprimise between fuel economy and power? Wouldn't it be chaper? I know nothing about programming a computer, so maybe I am missing something here. I do realise that on paper things would be figured for the specific conditions given, such as the standard atmosphere, but shouldn't the basic program of the PCM compensate for the differences of the actual conditions compared to the standard?"
Its gets complicated pretty quickly. For fuel economy the engine has more parasitics at high RPMS, the unlocked torque converter is more efficient at high RPMs, as you move away from a 1:1 gear ratio efficiency drops, at high PRMs the tranny pumping losses increase, ... When you start modeling all the individual parts of the system it gets hairy. So, that's why I decided just to measure the efficiency and treat the H3 as a black box instead of predicting the system efficiency.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/15/2006 6:29:11 PM
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Linus Gump
Posts: 960
Status: offline
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The last answer is what I was looking for. The classes that I was refering to are part of a commercial aviation degree, so all of the stuff about rho and airspeed vs ground speed are nothing new to me. Our test mule in class was an aircraft we are all familiar with and did some of these calculations in it to show what we already knew from flying it. I am aware that sitting at a desk and crunching numbers gives you a theoretical apsect to things, but when the engineers are designing something, this is where they start. I was just curious why this same principal wouldn't work to get the tune you are looking for, that's all.
Google is a great friend when it comes to making things simple, but we had to do it the old fasioned way, you know, with a pencil and paper.
Thanks to both of you for your responses.
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RE: My PCM tuning with PCMforLess.com - Process and Res... - 10/15/2006 7:21:13 PM
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HummerGuy
Posts: 6679
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I don't think I have ever felt more intimidated (in a good way) in my life as I do right now reading this stuff :) Now I understand how the attorneys I work for feel when I'm fixing their computers!
Well, I'm going to relax tonight, but so far, here are my findings:
First and foremost, there is no low-end dragging stalling pickup like there was before. When shifting into first off a stop, even if you floored it, sometimes it would take a while to get going before you felt the acceleration kick in. Now, it's very quick right when you take your foot off the clutch. It doesnt start off slow then get faster as you go (as far as the speed the acceleration picks up). It now seems like there is more low-end torque before you hit mid-range on the tach then less low-end torque like before. This is a HUGE deal to me, because I always felt like the engine was being sufficated and didn't have enough gas or air to get going. Now, it's awsome.
There is also a noticable difference in high-end torque, specifically once you hit 4500 RPMs. It's almost like a turbo-charger kicks in and pulls you back in your seat. It's not as noticable obviously in 3rd 4th and 5th gears as it is in 1rs and 2nd, but it's there.
Since I have a stick, I don't notice much of a power increase in passing, unless I downshift, but it's there. The throttle definitely seems more responsive when you punch it just casually driving down the street. Again, it seems like alot of the delays that were there between pressing the accelerator and the engine actually moving has almost dissappeared. It could just be me, but I notice it.
Obviously I don't know if my MPG has gone up since I've been driving so spuratically, but I'll figure that out after I burn off this first tank of gas. So far though, as much as I've been punching it, I am getting about the same mileage as I did just with casual driving, so that seems like a good sign.
The engine idles very smoothly. I am running 93 octane so that might have something to do with it (I'm still learning all about that from you guys). There is absolutely no vibration when in idle and you can't hear the engine at all. The engine seems a little quieter then it was before with the same gas. There was a VERY slight backfiring when I revved the engine the first time I started the engine after I replaced the PCM, but that seems to have dissappeared.
Also, there has been NO stuck throttle problem. THANK YOU! It started doing it again yesterday before I swapped the PCM's, but with this new tune, it hasn't happened once and I have driving about 200 miles already. It may just be a coincidence, but so far, it hasn't been stuck once. We'll see how that goes.
So, overall, I know nothing about the drag coefficient and dingle dongle doohickees but I can tell you to me it was worth it. It remedied the problems I had with lacking acceleration off the line, and I can actually accelerate in 5th gear on the expressway at more then a 1 MPH every 2 seconds rate! (That is MY scientific calculation)
I'm very please with the results. I'm sure things will start working better and I'll notice more little things that I haven't so far. I have only been able to floor it off the line 2 or 3 times because A) my wife has been in the car the entire time and B) Every FREAKIN stop light or sign I have been up to I have been stuck behind slow people. BLAH.
As soon as I figure out if I'm getting better mileage, I'll let you guys know, but overall, I'm happy with it. I have no complaints. No security relearn or check engine lights came on. It started right away with absolutely no problems. I'm going to recomment Alvin to a couple of my Chevy vette owner friends and see if he can tune them. I think it was definitely worth it. I can't wait to really drive this thing this week to work and back and see what it can do.
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