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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Negative LTFT at Idle



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      02-10-2021, 06:03 PM   #1
NRigs
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I have been noticing my LTFT at idle has been pretty low around -9 to -10%. I reset lamba adaptations and was able to log it to show it going from 0% down to -10% at idle. when I apply light throttle the LTFT does go back up towards 0%. Shouldn't LTFT at idle be close and remain at 0%? what could cause the LTFT to slowly drop to these levels?

here is the log
https://datazap.me/u/nrigs/idle-nega...18&zoom=38-446

Car is custom tuned by Steven at Wedge
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      02-12-2021, 09:05 AM   #2
anjuna
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Incorrect fueling at idle is the short and simple answer.

But is this really a problem? No.

Hell, I知 sitting in my own car with ~315 revisions to my tune right now and I知 getting +12% LTFT at idle.

Idle does some weird stuff - fueling is different, ignition is different, and everything is running on closed loops to try and make idle nice and happy. If you want to see something really wild, look at your ignition timings at idle

As long as your driveability is good, you池e not seeing ignition corrections, and boost/load is under control, ya good.
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      02-12-2021, 09:24 AM   #3
NRigs
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Quote:
Originally Posted by anjuna View Post
Incorrect fueling at idle is the short and simple answer.

But is this really a problem? No.

Hell, I知 sitting in my own car with ~315 revisions to my tune right now and I知 getting +12% LTFT at idle.

Idle does some weird stuff - fueling is different, ignition is different, and everything is running on closed loops to try and make idle nice and happy. If you want to see something really wild, look at your ignition timings at idle

As long as your driveability is good, you池e not seeing ignition corrections, and boost/load is under control, ya good.
When the car is warm everything is great. Just trying to figure out the stalling issue I have at cold starts. Car is an automatic and shouldn't be stalling 5 times before I can get out of my garage at my apartment building. The cold weather could be doing something, but the car doesn't have this issue with an OTS map.
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      02-12-2021, 09:25 AM   #4
NRigs
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I sent these logs to my tuner to see what he thinks and to see if he can tune this out.

Cold Start Idle - High Fuel Pressure at 90 seconds
https://datazap.me/u/nrigs/high-fuel...-11-15&solo=15


Warm Start Idle - LTFT drops to -9% (Other times I have seen idle around -11%)
https://datazap.me/u/nrigs/stage-2-i...=11-15&solo=15


Warm Start Idle Stage 2 OTS map
https://datazap.me/u/nrigs/stage-2-i...g=0&data=11-15
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      Yesterday, 10:40 PM   #5
Mdilo
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Quote:
Originally Posted by NRigs View Post
I have been noticing my LTFT at idle has been pretty low around -9 to -10%. I reset lamba adaptations and was able to log it to show it going from 0% down to -10% at idle. when I apply light throttle the LTFT does go back up towards 0%. Shouldn't LTFT at idle be close and remain at 0%? what could cause the LTFT to slowly drop to these levels?

here is the log
https://datazap.me/u/nrigs/idle-nega...18&zoom=38-446

Car is custom tuned by Steven at Wedge
Did you ever figure this out? I知 having the same issue and the same tuner.
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