Terrible Lean at Idle with AC-on
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Terrible Lean at Idle with AC-on Hello All,
I have been tuning for quite some time. But I've had a constant nagging problem that I just can't seem to get rid of. I have two main problems, first let me tell you about my setup.
I have EFILive COSv5 OLSD tune with two LC-1's (one is not working right now).
First problem I've had forever is a lean cold startup. The only way I've gotten to combat this problem is to command a extremely rich AFR as the motor warms up to counteract the lean condition.
My other problem is a super lean condition when I have the AC on at idle. It goes all the way to 20:1 AFR at idle when I have the AC on, I don't really understand it so much. Only thing I noticed is my IAC steps go all the way up to 170's when it does this. What is causing this?
I have my tune available if anyone wants to help me out, also, have startup logs and the log of the extremely lean AC-on idle condition.
Thanks,
Adrian
I have been tuning for quite some time. But I've had a constant nagging problem that I just can't seem to get rid of. I have two main problems, first let me tell you about my setup.
I have EFILive COSv5 OLSD tune with two LC-1's (one is not working right now).
First problem I've had forever is a lean cold startup. The only way I've gotten to combat this problem is to command a extremely rich AFR as the motor warms up to counteract the lean condition.
My other problem is a super lean condition when I have the AC on at idle. It goes all the way to 20:1 AFR at idle when I have the AC on, I don't really understand it so much. Only thing I noticed is my IAC steps go all the way up to 170's when it does this. What is causing this?
I have my tune available if anyone wants to help me out, also, have startup logs and the log of the extremely lean AC-on idle condition.
Thanks,
Adrian
First off, I have HPtuners, so I can't help with specific things to change, but as far as the lean cold startup, I know that it's a function to control emmisions since a cold motor doesn't burn completely compared to a warm motor. There should be some type of table that you can alter the bias from engine coolant temp to air temp. That and you can do just as you are saying and command a richer afr based on engine coolant temp as well.
In HPT it's under tq mngmgnt (dont mean trans!)...
There are theoretical tq-loss models for accessory load, and specific tables just for A/C. When the Ac runs it loads the engine down at idle, and the tq loss model opens the IAC to help compensate for the load at idle. Most people who have a setup that needs OLSD are no longer running A/C, so this isn't a common issue at all. I can't think of an easy way around it. If you remove the extra airflow from the AC tables, the odds are that it won't idle worth a fart with the AC on. It's an interesting issue though.
There are theoretical tq-loss models for accessory load, and specific tables just for A/C. When the Ac runs it loads the engine down at idle, and the tq loss model opens the IAC to help compensate for the load at idle. Most people who have a setup that needs OLSD are no longer running A/C, so this isn't a common issue at all. I can't think of an easy way around it. If you remove the extra airflow from the AC tables, the odds are that it won't idle worth a fart with the AC on. It's an interesting issue though.
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The way I combat the poor idle conditions when AC is on, is to just have a higher idle set under the Desired Idle Table. But for some reason, now i'm getting a terrible lean condition...still investigating. Thanks for the lead!
Adrian
Adrian
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Alright, i think i got it. I forgot that I did mess with the AC Torque loss table, increased it, thinking it would better my idle, so I returned it back to stock. Thanks for the pointer Frost!
Best,
Adrian
Best,
Adrian
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Alright, still having the same problem. Could it be that I have my regular idle set at 800 rpms, and AC-on idle set at 1050? When I first trip the AC, my AFR stays fine when idle rises to 1050. After a couple mins, then it starts to get worse and worse to the point where AFR is maxed at 20:1 AFR. This is driving me crazy as I like AC and would like to use it during the summer haha.
Thanks,
Adrian
Thanks,
Adrian
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Here's what worked for me. OLSD.
Heads, headers, cam (239/251, 106), 90mm TB and Fast 90mm.
B4354 "A/C Airflow Ramp In" - set all-> 5.00 g/sec
B4356 "A/C Torque Loss" ->increase all 15%
B4357 "A/C Torque Loss - IAT->increase all 15%
B4360-"A/C Torque Loss Correction" ->increase all 25%
B4361-"A/C Torque Loss Correction Ramp Out" -> increase all 40%
Heads, headers, cam (239/251, 106), 90mm TB and Fast 90mm.
B4354 "A/C Airflow Ramp In" - set all-> 5.00 g/sec
B4356 "A/C Torque Loss" ->increase all 15%
B4357 "A/C Torque Loss - IAT->increase all 15%
B4360-"A/C Torque Loss Correction" ->increase all 25%
B4361-"A/C Torque Loss Correction Ramp Out" -> increase all 40%
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Thats the ultimate goal, but first I have to work out ALL bugs in open loop FIRST. 
Bink: I've got it all, 427 LS2 with LS7 topend, 242/256 113+3LSA cam, headers, UD pulley, 42lb injectors, etc....
I'm not sure about adding more torqueloss, but I will give your setting a run and see if it helps my problem. Thanks for the excellent reply!
I'll let you know tomorrow how it works,
Adrian
Bink: I've got it all, 427 LS2 with LS7 topend, 242/256 113+3LSA cam, headers, UD pulley, 42lb injectors, etc....
I'm not sure about adding more torqueloss, but I will give your setting a run and see if it helps my problem. Thanks for the excellent reply!
I'll let you know tomorrow how it works,
Adrian
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You know, honestly, i think its just adding too much air, i think i'll go the opposite direction and cut it all 15% and see how that works. I noticed a little better AFR when I reduced the AC torqueloss values almost all to zero, so I'm going to keep heading in that direction. Once again, updates to come.
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Alright, getting frustrated! I zeroed out ALL of my A/C corrections and its still leaning out. This is what I'm seeing.....at idle, when i flip the AC on, the IAC steps goes up to 200 and leans the idle out to 20:1. Like I said, i've zeroed out all of my AC correction tables.....
Anyone with any other ideas?
Anyone with any other ideas?
silly question, but what RPM is being commanded at idle for AC-ON? Is it higher? There are some other tq compensation tables for accessory loading, check those out as well to be thorough.
If the IAC jacking is found to be the culprit, which it almost certainly must be, the changes Bink outlined will further exaggerate your condition. If this is the only issue you have left, why not just move back to closed loop? Just re-enable STFTs, leave the LTs off.
If the IAC jacking is found to be the culprit, which it almost certainly must be, the changes Bink outlined will further exaggerate your condition. If this is the only issue you have left, why not just move back to closed loop? Just re-enable STFTs, leave the LTs off.
Last edited by Frost; Jun 10, 2008 at 12:00 PM. Reason: spelling
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Hey Frost,
I checked out my Engine Compensation/multiplier tables as well. The most that is commanded there was 1.85 g/s. I reduced that down to a max of .3 g/s. I think that maybe the culprit in this entire mess. I'm going to try it out tomorrow, and I also returned the A/C settings back to stock since changes to that didn't affect the condition at all. My idle is set at 1050 rpms hot w/ac-on, 750 rpms hot w/ac-off. I tried setting my ac-on idle to 800 rpms with the same ill lean effects.
This AC issue is the only issue that I have left. Reason why I don't go back to closed loop is I'd like to prove that you can do a complete open loop speed density tune that will work year round in all weather conditions. Once I have that all setup, and working, then I'll finally concede, and go back to a CL SD tune
I enjoy the challenge, although it can be a bit frustrating at times! And man, i think i just broke my pinky toe! F***!
I checked out my Engine Compensation/multiplier tables as well. The most that is commanded there was 1.85 g/s. I reduced that down to a max of .3 g/s. I think that maybe the culprit in this entire mess. I'm going to try it out tomorrow, and I also returned the A/C settings back to stock since changes to that didn't affect the condition at all. My idle is set at 1050 rpms hot w/ac-on, 750 rpms hot w/ac-off. I tried setting my ac-on idle to 800 rpms with the same ill lean effects.
This AC issue is the only issue that I have left. Reason why I don't go back to closed loop is I'd like to prove that you can do a complete open loop speed density tune that will work year round in all weather conditions. Once I have that all setup, and working, then I'll finally concede, and go back to a CL SD tune
I enjoy the challenge, although it can be a bit frustrating at times! And man, i think i just broke my pinky toe! F***! 
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No, the IAC valve is not stuck open. When I turn on the AC, the computer opens it up (200 steps), causing the lean idle condition, once I turn off the AC, it returns it back to normal idle condition (10-30 steps). This also is only a problem AT idle, not while driving. I can have the AC on while driving with no problems. This is only an idle issue.
Thanks!
Adrian
Thanks!
Adrian
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Well, thats what I thought at first as well, so i moved it down to 800 rpms (50rpms higher then ac-off) with AC-on, still did the same exact thing. IAC counts moved up to 200 steps. Even when I had my normal idle set at 950 rpms with 1050 rpm ac-on, it would still do the exact same thing, plus at 950 rpms, my IAC counts weren't 200, they were 20-30 haha. Its entirely possible that I just may need to jack up my VE value at that range. I'm using a TPSvs RPM VE map for idle/cruising conditions, so 0 throttle and 1000 rpms I can just jack up VE for AC-on conditions....