WOT Tuning Without a Wideband - A Discussion
07-08-2003, 10:11 PM
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WOT Tuning Without a Wideband - A Discussion
The following is a discussion Dan K and I had regarding my theory and real life results of what I was able to do to get my AFR, while in PE mode, dialed in without the use of a wideband O2 sensor. I use Tunercat and Datamaster.
Ben: After my mods, I found that my MAF table calibrations were way off. In fact at peak RPM and MAP (MAF reading of 260 AFGS), I was showing 9% less air was flowing than optimum (128 BLM). Since this was nonlinear (I was dead on vs. my stock table calibration at around 110 AFGS), I could not adjust like others have suggested such as modifying the injector constant.
Dan: When you say that you were around 9% off at 260 G/S...how did you figure that? Is that just the long term fuel multiplier in a percentage form rather than counts?
Ben: Correct. I was showing approx. 139 on my Long Term Fuel Trims when I was in cell 15 at maximum RPM and MAP. How did I know? Keep reading.
D: This is based on 128 being ideal, correct?
B: Well, elimination of the fluctuations of the BLM's within cell 15 was most critical to me. Of course I want to try to hit 128 if I can.
B: How I found out was by eliminating PE for a few runs while I took data. I did this going to the "MAP Threshold to Enable WOT" table and putting this constant to 255. Once I did this and ran my full RPM range at 100% TPS, I saw my BLM's go leaner and leaner the higher the RPM's.
B: Remember it was a nonlinear MAF calibration error that maybe the computer would compensate for at the start of the cell RPM and MAP, while in PE mode, but could not at the end because I was increasingly leaner and leaner than the original cell BLM indicated.
D: The BLM's were getting leaner because you weren't adding in the extra fuel from the pe tables.
B: No. the BLM's in cell 15 got increasingly lean (kept increasing) because the MAF was giving out an incorrect calibration and the computer had to compensate by adding more and more fuel to keep it at stoich. (14.7:1) AFR. At max RPM and MAP, before recalibration, I was showing approximately 236 AFGS. The computer calculated the stoich. fuel needed and added the the incorrect amount for stoich plus 9% more to get the 02's to read stoich. Thus my recalibration of the MAF tables to 260 AFGS (9% increase in air). Some things to note here: I go into cell 15 at 2800 RPM (stock I think is 2000). for me, I reach cell 15 with my MAF at approx. 115 AFGS. So for others, you could be reaching cell 15 at as low as 80 AFGS. In essence we are allowing one cell to use 70% or more of our MAF table without us knowing if we are correct.
D: So what you're saying is that as RPM increased in cell 15 at WOT, you saw the BLM rise as the computer added fuel?
B: Correct while PE was disabled. The computer added fuel to maintain stoich.
D: That's exactly what the PE tables should correct, right?
B: No. PE tables add fuel based upon the last BLM within that cell. ****With this last statement, I know I am stepping on some toes of some who theorize the BLM's go to 128 in PE without a fuel modifier. However it is the only way to answer what happened.****
D: I agree with your thinking that PE does add fuel based on the last BLM in that cell.
B: As for your concern about being at 14.7:1 AFR during WOT, I agree that this is bad for long periods. However, this should be done for testing only. In addition, we have KR that will come into play here if knock is detected.
D: No. BAD!
B: I won't disagree with you here since I do not have enough knowledge in this arena.
D: I just don't understand if you're implying that we will get knock retard due to the lean condition? I know I've seen that happen before on the dyno, but I'm still unsure if it is something to be recommending to others to do. I wouldn't suggest to anyone to run there car that lean at WOT for any period of time. On a stock(ish) car I'll agree that you could probably get away with it easier than on a 425rwhp 396. That wouldn't be good.
B: Again I have not enough knowledge, but for testing purposes 30 seconds worth of WOT (4-6 runs) seem doubtful to be an engine damager. Remember, we are not lean, we are at stoich. throughout the run. But if this is a concern, just take a few degrees or more of timing out at your highest MAP's during testing and feel better about it. Now techies will argue that changing timing changes AFR, but I doubt highly it is enough for us to worry about when we talk a few degrees.
D: Knock retard isn't just caused by a lean condition. Knock and too little fuel can make the car go boom!
B: I don't want to go into what is knock and causes of it here as that is a HUGE discussion itself.
D: But I guess that as long as the long term fuel trim is correcting the injector pulsewidth you should be safe.
B: Now after recalibrating my MAF tables, I went to the dyno for the first time ever and wideband tested. I found I was on target with my estimated AFR vs. wideband AFR. I know for a fact that I would have been lean had I gone in without my BLM's checked in cell 15 and my MAF tables modified.
D: Ahh...here is where this gets interesting and why you have me very curious if you're way is a life saver. After disabling PE mode and modifying the MAF tables, you then put the car on a wideband and the AFR spit out was the same as what? In other words, where did you're estimated AFR come from? If so, I'm all ears. Actually the formula is WOT AFR = 14.7 / (1 + %Change vs Cool/100 + %Change vs RPM/100), but since you've zeroed the PE vs RPM table you've removed that from the equation?
I'd love to get that formula to be even remotely close.
B: For me at wideband test time, my "% change to AFR vs cool" was 14.5. This gave an effective PE AFR of 12.84 using the above equation. This is where it was cool: the wideband showed me to be at 12.8 AFR (with fluctuactions of + or - 0.1) from 3600 RPM to 5900 RPM where I shut down. This is with the "% change to AFR vs RPM at WOT" table completely zeroed!
D: What I'm thinking is this (let me know if I'm on the same track as you or if I've de-railed):
If you can accurately modify the MAF tables to where your BLM is always around 128 (126-130) then you have your 14.7:1 stoich. AFR that the computer shoots for. By correctly adjusting your MAF tables, and hence stoichiometric cell 15 fueling, then the corrections that are applied by the PE tables (when enabled) for WOT can be accurately used in that formula to calculate approximate AFR?
B: This is what I theorize and proven for myself (but me only).
D: On the other hand, by locking cell 15 to 128 you aren't actually changing cell 15 to 128. The computer still knows what it's long term correction is, you've just locked its ability to vary itself.
B: This is what I have to theorize.
B: These learned fuel trims for me at PE are still a question mark. When I reprogrammed for my 3rd and 4th run, my AFR in the 3600 to 5900 RPM range was at 13.3:1 (+ or - 0.1). Since I had never ran in cell 15 after the program (I was still on the dyno), the car never had a chance to compensate to a correct BLM to use in PE mode. When I originally went to the dyno/wideband, I was not perfect on my BLM's. I in fact was running rich by approx. 3% in cell 15. But I was consistently rich, not increasing or decreasing BLM's as I went through the RPM range. Remember, I solved that problem. So these 3rd and 4th runs still have me scratching my head.
B: Oh and BTW, I am not perfect on my PE AFR below 3600 RPM. I am lean here. Why? I have no idea. I went through the whole RPM range with my PE eliminated testing and was consistent in cells 12-15. This is another area I have not figured it out and other input is needed. I am sure it has to do with calibration of the lower 1/2 of my MAF tables. Yet, I have no fluctuations in my other cells.
D: Anyways, with cell 15 locked at 128 you haven't corrected the fueling in that cell in any way. And just like you found with your MAF tables being off in a non-linear fashion, as RPM increases and VE goes up, the need for fuel goes up. That's why if you take a PE vs. RPM table and apply it to the PE AFR formula you will see that on most, if not all, cars PE vs RPM fueling increases with RPM. It has to in order to make up for the non-linearly rising MAF tables.
B: I know stock may be this way, I cannot speak for other tunes.
D: If I understand you right, this is what you effectively did. You corrected the cell 15 fueling by correcting the MAF tables so that you'd have a BLM of 128. Then the PE AFR formula actually works correctly?
B: Well, to clarify, I was consistent not necessarily on dead on with my BLM's in cell 15.
B: Regarding locking your BLM's. I agree that is the thing to do at the dyno with the wideband and then keep it this way (BTW, I feel stupid I did not do this when I tested as I thought I had my BLM's on enough). However, what I am proposing is for those who are not going to the wideband and testing. If people do not check their calibration of the MAF's and their BLM's, they run the risk of being lean and have no way of knowing it. I am a case in point: at max RPM and MAP, I said I was 9% lean, with a % change in AFR vs cool temp of 15.9% at the time. This was before I was testing and even knew I had a problem. Obviously I was running lean and knocking to hell from it. How could I know I was lean since I had not put it on a wideband yet? The only way to know is to make sure my MAF is calibrated.
B: Now we could talk about someone's 02 sensors being wrong to begin with, but that is for another e-mail.
Thanks Dan K for the input. You made me think.
Please all give me your feedback to fill in the blanks for us.
Ben
Ben: After my mods, I found that my MAF table calibrations were way off. In fact at peak RPM and MAP (MAF reading of 260 AFGS), I was showing 9% less air was flowing than optimum (128 BLM). Since this was nonlinear (I was dead on vs. my stock table calibration at around 110 AFGS), I could not adjust like others have suggested such as modifying the injector constant.
Dan: When you say that you were around 9% off at 260 G/S...how did you figure that? Is that just the long term fuel multiplier in a percentage form rather than counts?
Ben: Correct. I was showing approx. 139 on my Long Term Fuel Trims when I was in cell 15 at maximum RPM and MAP. How did I know? Keep reading.
D: This is based on 128 being ideal, correct?
B: Well, elimination of the fluctuations of the BLM's within cell 15 was most critical to me. Of course I want to try to hit 128 if I can.
B: How I found out was by eliminating PE for a few runs while I took data. I did this going to the "MAP Threshold to Enable WOT" table and putting this constant to 255. Once I did this and ran my full RPM range at 100% TPS, I saw my BLM's go leaner and leaner the higher the RPM's.
B: Remember it was a nonlinear MAF calibration error that maybe the computer would compensate for at the start of the cell RPM and MAP, while in PE mode, but could not at the end because I was increasingly leaner and leaner than the original cell BLM indicated.
D: The BLM's were getting leaner because you weren't adding in the extra fuel from the pe tables.
B: No. the BLM's in cell 15 got increasingly lean (kept increasing) because the MAF was giving out an incorrect calibration and the computer had to compensate by adding more and more fuel to keep it at stoich. (14.7:1) AFR. At max RPM and MAP, before recalibration, I was showing approximately 236 AFGS. The computer calculated the stoich. fuel needed and added the the incorrect amount for stoich plus 9% more to get the 02's to read stoich. Thus my recalibration of the MAF tables to 260 AFGS (9% increase in air). Some things to note here: I go into cell 15 at 2800 RPM (stock I think is 2000). for me, I reach cell 15 with my MAF at approx. 115 AFGS. So for others, you could be reaching cell 15 at as low as 80 AFGS. In essence we are allowing one cell to use 70% or more of our MAF table without us knowing if we are correct.
D: So what you're saying is that as RPM increased in cell 15 at WOT, you saw the BLM rise as the computer added fuel?
B: Correct while PE was disabled. The computer added fuel to maintain stoich.
D: That's exactly what the PE tables should correct, right?
B: No. PE tables add fuel based upon the last BLM within that cell. ****With this last statement, I know I am stepping on some toes of some who theorize the BLM's go to 128 in PE without a fuel modifier. However it is the only way to answer what happened.****
D: I agree with your thinking that PE does add fuel based on the last BLM in that cell.
B: As for your concern about being at 14.7:1 AFR during WOT, I agree that this is bad for long periods. However, this should be done for testing only. In addition, we have KR that will come into play here if knock is detected.
D: No. BAD!
B: I won't disagree with you here since I do not have enough knowledge in this arena.
D: I just don't understand if you're implying that we will get knock retard due to the lean condition? I know I've seen that happen before on the dyno, but I'm still unsure if it is something to be recommending to others to do. I wouldn't suggest to anyone to run there car that lean at WOT for any period of time. On a stock(ish) car I'll agree that you could probably get away with it easier than on a 425rwhp 396. That wouldn't be good.
B: Again I have not enough knowledge, but for testing purposes 30 seconds worth of WOT (4-6 runs) seem doubtful to be an engine damager. Remember, we are not lean, we are at stoich. throughout the run. But if this is a concern, just take a few degrees or more of timing out at your highest MAP's during testing and feel better about it. Now techies will argue that changing timing changes AFR, but I doubt highly it is enough for us to worry about when we talk a few degrees.
D: Knock retard isn't just caused by a lean condition. Knock and too little fuel can make the car go boom!
B: I don't want to go into what is knock and causes of it here as that is a HUGE discussion itself.
D: But I guess that as long as the long term fuel trim is correcting the injector pulsewidth you should be safe.
B: Now after recalibrating my MAF tables, I went to the dyno for the first time ever and wideband tested. I found I was on target with my estimated AFR vs. wideband AFR. I know for a fact that I would have been lean had I gone in without my BLM's checked in cell 15 and my MAF tables modified.
D: Ahh...here is where this gets interesting and why you have me very curious if you're way is a life saver. After disabling PE mode and modifying the MAF tables, you then put the car on a wideband and the AFR spit out was the same as what? In other words, where did you're estimated AFR come from? If so, I'm all ears. Actually the formula is WOT AFR = 14.7 / (1 + %Change vs Cool/100 + %Change vs RPM/100), but since you've zeroed the PE vs RPM table you've removed that from the equation?
I'd love to get that formula to be even remotely close.
B: For me at wideband test time, my "% change to AFR vs cool" was 14.5. This gave an effective PE AFR of 12.84 using the above equation. This is where it was cool: the wideband showed me to be at 12.8 AFR (with fluctuactions of + or - 0.1) from 3600 RPM to 5900 RPM where I shut down. This is with the "% change to AFR vs RPM at WOT" table completely zeroed!
D: What I'm thinking is this (let me know if I'm on the same track as you or if I've de-railed):
If you can accurately modify the MAF tables to where your BLM is always around 128 (126-130) then you have your 14.7:1 stoich. AFR that the computer shoots for. By correctly adjusting your MAF tables, and hence stoichiometric cell 15 fueling, then the corrections that are applied by the PE tables (when enabled) for WOT can be accurately used in that formula to calculate approximate AFR?
B: This is what I theorize and proven for myself (but me only).
D: On the other hand, by locking cell 15 to 128 you aren't actually changing cell 15 to 128. The computer still knows what it's long term correction is, you've just locked its ability to vary itself.
B: This is what I have to theorize.
B: These learned fuel trims for me at PE are still a question mark. When I reprogrammed for my 3rd and 4th run, my AFR in the 3600 to 5900 RPM range was at 13.3:1 (+ or - 0.1). Since I had never ran in cell 15 after the program (I was still on the dyno), the car never had a chance to compensate to a correct BLM to use in PE mode. When I originally went to the dyno/wideband, I was not perfect on my BLM's. I in fact was running rich by approx. 3% in cell 15. But I was consistently rich, not increasing or decreasing BLM's as I went through the RPM range. Remember, I solved that problem. So these 3rd and 4th runs still have me scratching my head.
B: Oh and BTW, I am not perfect on my PE AFR below 3600 RPM. I am lean here. Why? I have no idea. I went through the whole RPM range with my PE eliminated testing and was consistent in cells 12-15. This is another area I have not figured it out and other input is needed. I am sure it has to do with calibration of the lower 1/2 of my MAF tables. Yet, I have no fluctuations in my other cells.
D: Anyways, with cell 15 locked at 128 you haven't corrected the fueling in that cell in any way. And just like you found with your MAF tables being off in a non-linear fashion, as RPM increases and VE goes up, the need for fuel goes up. That's why if you take a PE vs. RPM table and apply it to the PE AFR formula you will see that on most, if not all, cars PE vs RPM fueling increases with RPM. It has to in order to make up for the non-linearly rising MAF tables.
B: I know stock may be this way, I cannot speak for other tunes.
D: If I understand you right, this is what you effectively did. You corrected the cell 15 fueling by correcting the MAF tables so that you'd have a BLM of 128. Then the PE AFR formula actually works correctly?
B: Well, to clarify, I was consistent not necessarily on dead on with my BLM's in cell 15.
B: Regarding locking your BLM's. I agree that is the thing to do at the dyno with the wideband and then keep it this way (BTW, I feel stupid I did not do this when I tested as I thought I had my BLM's on enough). However, what I am proposing is for those who are not going to the wideband and testing. If people do not check their calibration of the MAF's and their BLM's, they run the risk of being lean and have no way of knowing it. I am a case in point: at max RPM and MAP, I said I was 9% lean, with a % change in AFR vs cool temp of 15.9% at the time. This was before I was testing and even knew I had a problem. Obviously I was running lean and knocking to hell from it. How could I know I was lean since I had not put it on a wideband yet? The only way to know is to make sure my MAF is calibrated.
B: Now we could talk about someone's 02 sensors being wrong to begin with, but that is for another e-mail.
Thanks Dan K for the input. You made me think.
Please all give me your feedback to fill in the blanks for us.
Ben
Last edited by 95Blackhawk; 07-10-2003 at 11:31 PM.
07-08-2003, 11:08 PM
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interesting reading material!
I always thought if you had BLMs of 128 that the PE table could be accurately adjusted w/o hooking up a wideband O2. the problem for me had been taking the time to get all my BLMs perfect. Since i was going to the dyno anyway i figured i would save myself all the work and just hook up a wideband for a little extra and be done with it. good thing you have the time and ***** to prove the theory
I THINK the formula for WOT AFR = (14.7) / (1 + %Change vs Cool/100 + %Change vs RPM/100) is mostly true except for its needs to account for BLMs not being 128. if your BLM right before cell 15 is say 116 then you would need to add to the equation...(116/128)(14.7) = 13.3. but now when you are above 128 it just sticks with that higher BLM which is IMO a bad idea b/c the car could run lean at high RPMs but the original equation isnt affected... thats what i believe happens anyway.
I always thought if you had BLMs of 128 that the PE table could be accurately adjusted w/o hooking up a wideband O2. the problem for me had been taking the time to get all my BLMs perfect. Since i was going to the dyno anyway i figured i would save myself all the work and just hook up a wideband for a little extra and be done with it. good thing you have the time and ***** to prove the theory
I THINK the formula for WOT AFR = (14.7) / (1 + %Change vs Cool/100 + %Change vs RPM/100) is mostly true except for its needs to account for BLMs not being 128. if your BLM right before cell 15 is say 116 then you would need to add to the equation...(116/128)(14.7) = 13.3. but now when you are above 128 it just sticks with that higher BLM which is IMO a bad idea b/c the car could run lean at high RPMs but the original equation isnt affected... thats what i believe happens anyway.
Last edited by turbo_Z; 07-08-2003 at 11:12 PM.
07-08-2003, 11:34 PM
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Originally posted by turbo_Z
I THINK the formula for WOT AFR = (14.7) / (1 + %Change vs Cool/100 + %Change vs RPM/100) is mostly true except for its needs to account for BLMs not being 128. if your BLM right before cell 15 is say 116 then you would need to add to the equation...(116/128)(14.7) = 13.3. but now when you are above 128 it just sticks with that higher BLM which is IMO a bad idea b/c the car could run lean at high RPMs but the original equation isnt affected... thats what i believe happens anyway.
I THINK the formula for WOT AFR = (14.7) / (1 + %Change vs Cool/100 + %Change vs RPM/100) is mostly true except for its needs to account for BLMs not being 128. if your BLM right before cell 15 is say 116 then you would need to add to the equation...(116/128)(14.7) = 13.3. but now when you are above 128 it just sticks with that higher BLM which is IMO a bad idea b/c the car could run lean at high RPMs but the original equation isnt affected... thats what i believe happens anyway.
The formula for the GN ECM is as follows:
Injector Constant * RPM * MAF table value * Fuel Trim * AFR *MAF Constant * MAF Table Scaler * BLM * Integrator
Of course there are some things there that the LT1 ECM doesn't have...but you get the point.
See guys, if we can figure out exactly what goes into determining wot (or pe) fueling, then maybe we can start to take out some of the variables and get the formula to point where it is actually usable.
With Ben's method of disabling PE mode and running the car at wot, he is finding a way to eliminate the blm portion of that formula.
The more we break that formula down (once we know what it actually is) then it will be easier to get the wot afr fairly close without needing a wideband.
Then the wideband would be for verification of our work.
07-09-2003, 12:16 AM
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the solution is simple... just get your BLMs to 128 in cell 15 after disabling PE or BLM locking in that cell. but of course the problem arises when you go to adjust the MAF table. in a WOT run there isnt enough time to allow the PCM to make the corrections unless you increase 500 rpms about every 5 sec or so and continue that till you reach 6000 rpm. with a AFR of 14.7:1 im not sure thats a great idea.... just guessing here. then when you gather your data, you must adjust the MAF table accordingly but how much is too much or too little? you might end up repeating the process several times and that lean AFR comes into play again.
07-09-2003, 12:29 AM
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If you lock cell 15 to 128, have you actually changed what cell 15 learned to to 128 or have you just taken away it's ability to change? If cell 15 learns to 120 than it is always going to be removing fuel, but if you lock it to 128 have you actually changed it to 128? I'm still a little unclear on that.
I'm also unsure of disabling pe mode and running the car at a stoichiometric a/f ratio. I just can't bring myself to try it yet.
Ben, when you saw your blm at 139 in cell 15...how did you use that to change the maf table? Did you multiply the maf table in that g/s range by something?
I'm also unsure of disabling pe mode and running the car at a stoichiometric a/f ratio. I just can't bring myself to try it yet.
Ben, when you saw your blm at 139 in cell 15...how did you use that to change the maf table? Did you multiply the maf table in that g/s range by something?
07-09-2003, 01:21 AM
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Originally posted by Dan K
If you lock cell 15 to 128, have you actually changed what cell 15 learned to to 128 or have you just taken away it's ability to change? If cell 15 learns to 120 than it is always going to be removing fuel, but if you lock it to 128 have you actually changed it to 128? I'm still a little unclear on that.
If you lock cell 15 to 128, have you actually changed what cell 15 learned to to 128 or have you just taken away it's ability to change? If cell 15 learns to 120 than it is always going to be removing fuel, but if you lock it to 128 have you actually changed it to 128? I'm still a little unclear on that.
07-09-2003, 07:28 AM
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Originally posted by turbo_Z
but of course the problem arises when you go to adjust the MAF table. in a WOT run there isnt enough time to allow the PCM to make the corrections unless you increase 500 rpms about every 5 sec or so and continue that till you reach 6000 rpm.
but of course the problem arises when you go to adjust the MAF table. in a WOT run there isnt enough time to allow the PCM to make the corrections unless you increase 500 rpms about every 5 sec or so and continue that till you reach 6000 rpm.
RPM's in cell 15.
Originally posted by turbo_Z
with a AFR of 14.7:1 im not sure thats a great idea.... just guessing here. then when you gather your data, you must adjust the MAF table accordingly but how much is too much or too little? you might end up repeating the process several times and that lean AFR comes into play again.
with a AFR of 14.7:1 im not sure thats a great idea.... just guessing here. then when you gather your data, you must adjust the MAF table accordingly but how much is too much or too little? you might end up repeating the process several times and that lean AFR comes into play again.
Thanks all for the input.
Ben
07-10-2003, 09:44 AM
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FWIW, I am almost certain that the stock behavior of BLMs at WOT is that if they are < 128, they will lock at 128. If they are > 128, they will lock at what they were before WOT.
The reasoning is that it's not "bad" for the car to run overly rich at WOT (< 128 = too much fuel, so removing; but it doesn't want to take the chance that the removing of fuel might adversly affect other RPM points affected by the same BLM so it reverts to not changing the existing fuel; i.e., staying at 128), compared to running overly lean (> 128 = not enough fuel, so adding).
Ben talking to me about this idea of tuning and I thought it was a good idea too. The only thing, which I never mentioned, was that I was a bit concerned about running at 14.7:1 at WOT, as well. But I don't feel this is lean enough for the short periods of time needed to tune to cause any damange. Of course, more experienced engine builders would know more surely.
The reasoning is that it's not "bad" for the car to run overly rich at WOT (< 128 = too much fuel, so removing; but it doesn't want to take the chance that the removing of fuel might adversly affect other RPM points affected by the same BLM so it reverts to not changing the existing fuel; i.e., staying at 128), compared to running overly lean (> 128 = not enough fuel, so adding).
Ben talking to me about this idea of tuning and I thought it was a good idea too. The only thing, which I never mentioned, was that I was a bit concerned about running at 14.7:1 at WOT, as well. But I don't feel this is lean enough for the short periods of time needed to tune to cause any damange. Of course, more experienced engine builders would know more surely.
07-10-2003, 09:04 PM
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Originally posted by rskrause
Not of this makes any sense unless the motor were absolutely stock. That's what the equation is based on. And I wouldn't trust my motor to it anyway.
Not of this makes any sense unless the motor were absolutely stock. That's what the equation is based on. And I wouldn't trust my motor to it anyway.
I don't understand why you think it makes no sense. If you can rule out a variable in an equation don't you make the equation easier to solve?
That's all Ben was trying to do, and all I was trying to understand.
I'd like to see the real equation that the ECM uses instead of the WOT AFR = 14.7 / (1 + %Change vs Cool/100 + %Change vs RPM/100), because I'm sure that is just a simplified version of it.
You're right though, we may be chasing our tails...but Bens method worked on his car.
Just not sure if anyone else wants to try it on theirs.
07-10-2003, 11:01 PM
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Originally posted by Dan K
Ben, when you saw your blm at 139 in cell 15...how did you use that to change the maf table? Did you multiply the maf table in that g/s range by something?
Ben, when you saw your blm at 139 in cell 15...how did you use that to change the maf table? Did you multiply the maf table in that g/s range by something?
I did this along all the MAF tables by using Excel to graduate an increase from where my calibration was on at 110 AFGS to where I would increase by 9% at (in this case) 236 AFGS giving me 260.
Rich,
I agree not all of this makes sense, which is why I posted it for others to give input on. What exactly do you feel does not make sense?
As for totally understanding it, I do not (like why am I still lean utilizing this below 3600 RPM) but the results say it all. I am shocked to be able acheive an AFR that has less than a 1% variance from where I "estimated" before hitting the wideband. Just want others to know they may have the same success as me - if they want to try.
Ben
07-10-2003, 11:21 PM
#12
Registered User
Join Date: Dec 1999
Location: Houston, TX
Posts: 2,249
Ben: Are you using a stock cam? What are the specs if aftermarket?
I am guessing (by my trap speeds) that I was in the 310-320 rwhp range (107.5 trap speeds @ ~3500lbs). I say this because you could have ported heads and a stock cam and be close in MPH/rwhp to my car.
My point is that if you WERE using the stock cam, the formula (as Rich posted) would work well with you.
I am/was/am/was (
) tempted to try this, but VERY hesitant.
Ryan
I am guessing (by my trap speeds) that I was in the 310-320 rwhp range (107.5 trap speeds @ ~3500lbs). I say this because you could have ported heads and a stock cam and be close in MPH/rwhp to my car.
My point is that if you WERE using the stock cam, the formula (as Rich posted) would work well with you.
I am/was/am/was (
) tempted to try this, but VERY hesitant.Ryan
07-10-2003, 11:44 PM
#13
Registered User
Thread Starter
Join Date: Jul 2002
Location: Phoenix, AZ
Posts: 1,277
Originally posted by 96-speed
Ben: Are you using a stock cam? What are the specs if aftermarket?
I am guessing (by my trap speeds) that I was in the 310-320 rwhp range (107.5 trap speeds @ ~3500lbs). I say this because you could have ported heads and a stock cam and be close in MPH/rwhp to my car.
My point is that if you WERE using the stock cam, the formula (as Rich posted) would work well with you.
I am/was/am/was () tempted to try this, but VERY hesitant.
Ryan
Ben: Are you using a stock cam? What are the specs if aftermarket?
I am guessing (by my trap speeds) that I was in the 310-320 rwhp range (107.5 trap speeds @ ~3500lbs). I say this because you could have ported heads and a stock cam and be close in MPH/rwhp to my car.
My point is that if you WERE using the stock cam, the formula (as Rich posted) would work well with you.
I am/was/am/was (
) tempted to try this, but VERY hesitant.Ryan
Stock cam. I think the equation on PE is still valid. I am producing more HP by putting more air into my cylinder than I used to at stock...no matter how that is accomplished.
Do some research on running cars lean at WOT and see what others have said. I have done some research on the web and found nothing significant. Maybe I will.
Something to note, is I saw a couple of cars that went and dynoed run at 14:1 or so (this is bad and they were told they were lean). But again, this is the whole point! some of our cars may be running leaner than stoich. and we may not even know it.
Ok, I am posting on LT1 forum this question regarding lean and WOT.
07-11-2003, 09:12 AM
#14
Registered User
Join Date: Aug 2002
Location: Oshkosh, WI., United States
Posts: 192
With the help of Ben, I ran through the same procedure he did by turning off PE mode and now am locked at 128 BLM's through all cells +/- 2. With PE mode off I found I was running rich in all cells, some cells were as low as 112 BLM's. I also did not have a linear % I was off through my whole MAF tables. I was rich by 6% in my upper MAF tables, fairly close on my mid tables, and almost 9% rich on my lower MAF tables. I just now after repeated logging and adjustment of the MAF tables can say I'm running between 126 and 130 in all my cells. I could probably get it closer than this, but it's closet enough for now until the cam install. I realize this doesn't do much for closed loop, but I know that I'm entering cell 15 (PE mode) at 128 BLM's now and not 115 or so. I guess you can say his theory worked for me.
07-11-2003, 10:21 AM
#15
Registered User
Join Date: Dec 1999
Location: Houston, TX
Posts: 2,249
Originally posted by JAFO1994
I guess you can say his theory worked for me.
I guess you can say his theory worked for me.
I don't think anyone is disputing the BLMs being off at WOT.
Ryan