Car is STILL LEAN at WOT! LTFTs going negative at WOT! Please help!
05-27-2008, 01:49 PM
#1
Car is STILL LEAN at WOT! LTFTs going negative at WOT! Please help! I've been battling a lean condition at WOT for quite a while now. I originally thought it may be related to a fuel pressure issue being caused by a WOT voltage drop problem I was also having. See this thread for details https://ls1tech.com/forums/fueling-injection/913098-voltage-drop-wot-lean-condition-related.html
Anyway, I solved the voltage drop issue, but the lean condition is still there. My commanded AFR (PE vs RPM table) is set at 12.8:1. I keep scaling my MAF table higher and higher and it the lean condition is still there.
Now, I would normally suspect that this is being caused by a "mechanical" fuel pressure issue since my tuning efforts don't seem to change it. However, I've recently noticed in my logs that my injector pulse widths decrease at higher RPMs and my LTFTs are also going negative! WTF? I thought LTFTs would never go negative at WOT? I don't know how to post a log file, but I'd be glad to e-mail a few logs to anyone that can help me out. BTW, I'm logging with Auto Tap and tuning with Edit......old school, I know. Thanks in advance.
Anyway, I solved the voltage drop issue, but the lean condition is still there. My commanded AFR (PE vs RPM table) is set at 12.8:1. I keep scaling my MAF table higher and higher and it the lean condition is still there.
Now, I would normally suspect that this is being caused by a "mechanical" fuel pressure issue since my tuning efforts don't seem to change it. However, I've recently noticed in my logs that my injector pulse widths decrease at higher RPMs and my LTFTs are also going negative! WTF? I thought LTFTs would never go negative at WOT? I don't know how to post a log file, but I'd be glad to e-mail a few logs to anyone that can help me out. BTW, I'm logging with Auto Tap and tuning with Edit......old school, I know. Thanks in advance.
05-27-2008, 01:57 PM
#2
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LTFT's should go to 0 at WOT. You should be adding to your PE not screwing with the MAF tables for WOT fueling. Just because the programmer says its commanding 12.8 doesn't mean you'll actually get 12.8air/fuel.
05-27-2008, 02:21 PM
#3
As for modding the PE table, I was under the impression that the PE vs RPM value was just a commanded mulitplier for WOT fueling and that the MAF and VE Tables had to be providing a correct airflow value or the actual AFR would be wrong.
For example: My PE Vs. RPM table is set to 12.8:1 across the board. If my MAF table is reporting that I'm getting 354 gm/sec of air at 6300 RPM, the PCM will change the injector pulse width to add enough fuel to that 354 gm/sec of air to achieve a 12.8:1 AFR. However, lets say the MAF table is incorrect (uncalibrated) and I'm actually receiving 370 gm/sec of air at 6300, then my mixture will be lean since the MAF is only reporting 354 gm/sec. Maybe I'm incorrect on this. Please explain your reasoning for futher modifying the PE vs RPM. Thanks.
05-27-2008, 02:30 PM
#4
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Subscribing. Having same exact (almost) problem on 98 LS1 (in an 88GTA). I could have written you initial post. Injectors scaled correctly, VE and MAF dialed in good for all part throttle operation and MAF scaled for high speed too. Go into PE mode, go way lean. Commanding 11.5 now to get 12.5. I've tried bumping MAF up on the high end of scale w/ zero results.
Only difference, I don't get negative LTFTs. That I've never seen. You might want to log and check to make sure it's dropping into PE mode.
Only difference, I don't get negative LTFTs. That I've never seen. You might want to log and check to make sure it's dropping into PE mode.
05-27-2008, 04:06 PM
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If I'm tuning a car with the MAF still connected, then I try not to adjust the MAF tables unless there has been a descreening or something to alter the calibration. Otherwise, say SD mode, you'll have to modify the PE table to get your desired fuel ratio (imo) or work the VE table in say 2 or 3 barr mode.
What is your pcm set to for open loop/WOT operation? Are you seeing a full 100% command as far as pedal position goes?
What is your pcm set to for open loop/WOT operation? Are you seeing a full 100% command as far as pedal position goes?
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05-27-2008, 04:53 PM
#8
If I'm tuning a car with the MAF still connected, then I try not to adjust the MAF tables unless there has been a descreening or something to alter the calibration. Otherwise, say SD mode, you'll have to modify the PE table to get your desired fuel ratio (imo) or work the VE table in say 2 or 3 barr mode.
Probably just need to buy a new lid I guess.Is there anything else I may have disabled to keep it from going into PE mode that I'm not thinking of? I know I disabled PE mode when I was SD tuning, but I thought all I did was changed MAP to enable to 105 and made the PE vs RPM table all 1.00. As said before, those values are now MAP to enable 15 and PE vs RPM table to 1.1483; about 12.8:1.
05-27-2008, 05:08 PM
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There's also the dynamic airflow zone, should be 1 for WOT.
Are you sure you didn't miss setting anything else back to normal after the SD tuning?
05-27-2008, 05:09 PM
#11
OK, how about this.......I read somewhere on here to set your OLFA table to 1.00 because when in PE mode, the fueling will be based on the richer of the two tables (OLFA or PE vs RPM). So, I have all MAP points above 60C set to 1.00. Is it possible that my fueling is being based on this table instead of my PE vs RPM table? I'm still not sure that explains the negative LTRIMs at WOT though. Just trying to throw some things out there.
05-27-2008, 05:12 PM
#13
Can you log fuel trim cell? PE will be 20, 21 or 22. Can't remember which exactly but all three of those are cells where the system doesn't want any permanent changes to LTFTs.
There's also the dynamic airflow zone, should be 1 for WOT.
Are you sure you didn't miss setting anything else back to normal after the SD tuning?
There's also the dynamic airflow zone, should be 1 for WOT.
Are you sure you didn't miss setting anything else back to normal after the SD tuning?
I'm thinking there is something I didn't set back after SD tuning that I should have. I'm going through my tuning files and trying to find what's different, but I've lost some files due to my laptop crashing, so I don't have a complete history of my tuning progress.
05-27-2008, 05:18 PM
#14
Closed Loop enable temps are all at the stock settings. I compared it to my bone stock tune file. FWIW, LS1 Edit lists Closed Loop Enable Temps as coolant temps and not IAC temps. I don't know if that's a difference in model years, or just a wrong value lable in LS1 Edit.
05-27-2008, 05:23 PM
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Only 4 things I'm aware of that I changed (not counting spark).
DFCO enable temp = 284
LTFT = Disabled
Closed Loop Enable Temps = 284
Open Loop EQ = 1.00
The open loop EQ has got me thinking. Best I understand this you go into open loop when at WOT but you have a PE table that's supposed to be primary on WOT. Could the Open Loop EQ ratio be playing a part in this? I don't think so but that's not worth much.
DFCO enable temp = 284
LTFT = Disabled
Closed Loop Enable Temps = 284
Open Loop EQ = 1.00
The open loop EQ has got me thinking. Best I understand this you go into open loop when at WOT but you have a PE table that's supposed to be primary on WOT. Could the Open Loop EQ ratio be playing a part in this? I don't think so but that's not worth much.
05-27-2008, 05:32 PM
#18
What I don't understand is why they are going negative at WOT. LTRIMs should never go negative in PE mode. Prior to making my original post, it hadn't occured to me that it may not be going into PE mode, thus the negative trims at WOT. Thanks to the help of other posters, I'm now trying to figure out why it may not be going into PE mode. I believe once I get it to go into PE mode, the LTRIMS will zero out and quit pulling fuel.
05-27-2008, 05:35 PM
#19
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Closed Loop enable temps are all at the stock settings. I compared it to my bone stock tune file. FWIW, LS1 Edit lists Closed Loop Enable Temps as coolant temps and not IAC temps. I don't know if that's a difference in model years, or just a wrong value lable in LS1 Edit.
One is ECT vs. MAP, the other is ECT vs. IAT, both were set to 284 across the board when I was doing SD tune.
05-27-2008, 05:38 PM
#20
Only 4 things I'm aware of that I changed (not counting spark).
DFCO enable temp = 284
LTFT = Disabled
Closed Loop Enable Temps = 284
Open Loop EQ = 1.00
The open loop EQ has got me thinking. Best I understand this you go into open loop when at WOT but you have a PE table that's supposed to be primary on WOT. Could the Open Loop EQ ratio be playing a part in this? I don't think so but that's not worth much.
DFCO enable temp = 284
LTFT = Disabled
Closed Loop Enable Temps = 284
Open Loop EQ = 1.00
The open loop EQ has got me thinking. Best I understand this you go into open loop when at WOT but you have a PE table that's supposed to be primary on WOT. Could the Open Loop EQ ratio be playing a part in this? I don't think so but that's not worth much.