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Old 07-19-2017, 08:27 PM   #15
steve99
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Let the cars idle for a minute stationary
Check the afr and commanded afr both should be pretty close to 14.7 and fairly stable might go to 15 or 14.4 or so but outside that is unusual

Check the long term fuel trims at idle should be less than 10%

If you got unusual values check for intake or exhaust leaks dirty maf sensors clean connectors on maf and o2 sensors.

You can try bumping idle to 750 and setting the overun fuel resume to 1400 from 1300

But fix hardware ussues first
Seen couple if guys with bad front o2 sensors
Bad rear 02 usyally only effect cruise fueling

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Old 07-19-2017, 09:41 PM   #16
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OFT - Control Minimum RPMs?

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Originally Posted by steve99 View Post
.

You can try bumping idle to 750 and setting the overun fuel resume to 1400 from 1300

Edit: nevermind I read it wrong :P



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Old 07-19-2017, 11:49 PM   #17
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I found on petrol the stg 2 OFT tunes to be really good at idle. I am now on e85 stg 2 OFT and the idle is not as consistent. Not terrible but will occasionally bounce around. I have a light flywheel so just figured the e85 tune wasn't as sorted.
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Old 07-20-2017, 08:50 AM   #18
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Update, changing the PI/DI ratio tables didn't work for me. Might work for you guys with bigger injectors though, definitely worth a shot. It's only been one day but the car is relearning since I reflashed it and dipping as low as ever until it learns not to do that $hit... *sigh*
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Old 07-20-2017, 08:52 AM   #19
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Quote:
Originally Posted by steve99 View Post
Let the cars idle for a minute stationary
Check the afr and commanded afr both should be pretty close to 14.7 and fairly stable might go to 15 or 14.4 or so but outside that is unusual

Check the long term fuel trims at idle should be less than 10%

If you got unusual values check for intake or exhaust leaks dirty maf sensors clean connectors on maf and o2 sensors.

You can try bumping idle to 750 and setting the overun fuel resume to 1400 from 1300

But fix hardware ussues first
Seen couple if guys with bad front o2 sensors
Bad rear 02 usyally only effect cruise fueling
I did some data logging this morning, I'll take a look tonight. I'm pretty sure the car is just learning how low it can go, I just find it very frustrating haha we'll see if it persists but this is really good input, thanks!
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Old 07-20-2017, 10:11 AM   #20
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Same thing has been happening to me for months and months. I have a Tomei UEL and have tried several tunes, cleaned my MAF, air filter, bought new o2 sensors, injector orings replaced, new gaskets for my header and exhaust, yet this problem still persists.

I have noticed that when I have the A/C on, the problem becomes MUCH worse than when I turn the A/C completely off.

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I have been having this issue come up periodically even after putting hundreds of miles on the car after the flash. I'm running a Tomei UEL header with full catless exhaust on the OFT stage 2 e85 tune. Probably every 3 days it seems my car has trouble finding its idle. While monitoring with the OFT I see that the AFR seems to hunt around going up to mid 15s then jumps down to 13s which is where the car seems to bog down and almost stall sometimes turning off the headlights. I can't seem to find any reason as to why it happens though.
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Old 07-20-2017, 03:07 PM   #21
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Quote:
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I'm pretty sure the car is just learning how low it can go,
It's not this. There are other settings other than the Target Idle RPM. Correct MAF settings help, it seems having slightly negative trims help. Try increasing the Idle Airflow and Load maps (if they are there).
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Old 07-20-2017, 07:54 PM   #22
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Idle stability tables may help as well
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Old 07-20-2017, 07:57 PM   #23
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Quote:
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Idle stability tables may help as well
This tends to be more when blipping the throttle or revs dropping and less so if the idle is unstable, unless the stability tables are jacked up and ends up in oscillation.
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Old 07-20-2017, 10:09 PM   #24
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Is this only happening on aftermarket headers? Specifically UEL headers? I ask because if that's the case, then the folks with this problem might be running into a peculiarity with the idle control loop. Other than the Target Idle, are there other parameters we can adjust that have been defined? Haven't checked out the "idle stability tables" Steve mentioned, but those sound promising by title.

Maintaining a consistent idle might sound easy, but getting a machine to balance consistently is surprisingly complex. There are likely damping functions built in to the control loop to keep it from oscillating back and forth. Part of setting that up is adjusting for things like intake length, intake resonance, exhaust resistance, exhaust resonance, angular acceleration, etc. Making a change to ANY of these would mess with that control loop. If you change the header to a completely different design, you will have to adjust how the ECU maintains idle, or more likely than not deal with transient effects like this.
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Old 07-20-2017, 11:39 PM   #25
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Quote:
Originally Posted by Kodename47 View Post
This tends to be more when blipping the throttle or revs dropping and less so if the idle is unstable, unless the stability tables are jacked up and ends up in oscillation.

arh ok
well try the overrun fuel resume table maybe bump it to 1400 from 1300
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Old 07-20-2017, 11:48 PM   #26
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Quote:
Originally Posted by Spuds View Post
Is this only happening on aftermarket headers? Specifically UEL headers? I ask because if that's the case, then the folks with this problem might be running into a peculiarity with the idle control loop. Other than the Target Idle, are there other parameters we can adjust that have been defined? Haven't checked out the "idle stability tables" Steve mentioned, but those sound promising by title.

Maintaining a consistent idle might sound easy, but getting a machine to balance consistently is surprisingly complex. There are likely damping functions built in to the control loop to keep it from oscillating back and forth. Part of setting that up is adjusting for things like intake length, intake resonance, exhaust resistance, exhaust resonance, angular acceleration, etc. Making a change to ANY of these would mess with that control loop. If you change the header to a completely different design, you will have to adjust how the ECU maintains idle, or more likely than not deal with transient effects like this.

I have UEL header


have my base idle at 650
modded idle stability tables
full DI at idle


no stalls coming to stop
dips slightly on a/c cycling
and on rear demister turn on
but no stall or shaking just dips to say 550 then recovers
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Old 07-21-2017, 01:08 AM   #27
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Quote:
Originally Posted by steve99 View Post
I have UEL header


have my base idle at 650
modded idle stability tables
full DI at idle


no stalls coming to stop
dips slightly on a/c cycling
and on rear demister turn on
but no stall or shaking just dips to say 550 then recovers
Wasn't trying to suggest your setup or methodology is incorrect. I actually agree with you on the stability tables if they are what I think they are.

I was just attempting to point out that the shape of the header is a part of the idle control loop. Changing that is the same as messing with the ECU regarding idle stability.
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Old 07-21-2017, 06:21 AM   #28
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Quote:
Originally Posted by steve99 View Post
I have UEL header


have my base idle at 650
modded idle stability tables
full DI at idle


no stalls coming to stop
dips slightly on a/c cycling
and on rear demister turn on
but no stall or shaking just dips to say 550 then recovers


Can you elaborate on your idle stability tables?


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