Enlighten me
 

Someone please enlighten me.

LTFT is near perfecto doesn't move past 1.6%

IAM dead at 1

My tune is wonderful, scaled my MAF, I've changed ADVCS tables, throttle tip-in, DI, and changed pretty much everything recommended on this forum!

So...why are my STFT's varying so much when I press the throttle is it due to the tip-in? Or maybe the added DI?

I'd really love to know as to why this happens? Pretty sure I dont have any leaks anywhere because that would effect my LTFT right?

idk... come on guys help a fellow 86 brother out.

and if anyone knows any other "secrets" for me to further enchance my tune please share.... :thumbup: :thumbup: :thumbup: :thumbup: :bow: :bow: :bow:

Simplified explanation Open loop/Closed loop fuelling

Usually open loop is used on initial start and during warmup, until the 02 sensor reaches its operating temperature and produces a reliable signal , at which point the ECU switches to closed loop for idle. Warmup mode is Fuel System status =1

Under heavy acceleration or abrupt throttle movement the system will generally go open loop. Fuel system status =4

During cruise and idle it will generally be in Closed Loop mode Status = 2

When the engine is running in closed loop, it is using the signal from the O2 sensor to regulate the AFR in conjunction with the MAF sensor. There is a feedback "loop" between the O2 sensor and ECU so the ECU continuously makes adjustments based on the O2 sensor data.

The correction applied by the ECU due to the O2 sensor input will be in the form of STFT, if the STFT stays negative or positive consistently for a period of time it will be written to LTFT. There are several bands of LTFT based on MAF sensor flow rates (roughly related to engine RPM) where the ECU stores the LTFT. This is a continuous learning process and other offsets and compensations are applied due to IAT, Pressure , coolant temp ect.

In open loop the O2 sensor isn't used and the ECU sets fueling based on stored maps(OL fueling AFR target maps) the MAF sensor input and LTFT trims learned when engine was running in Closed loop mode.







STFT will always vary a lot with quick/large throttle movements in closed loop operation, this is the ecu keeping your AFR at the target in closed loop this is the CL fueling tables.


STFT will be zero in open loop , this is normal, only learned ltft is applied in open loop. The target afr is now the closed loop table.


LTFT is the average of these corrections based on how far off the measured afr was different from the commanded afr.


In short if your ltft is low throughout the rpm range and your commanded afr and measured afr are close in ol and cl operation your maf scaling is good. In closed loop its notmal for stft to vary as the ecu correct fueling for rapid changes in throttle.

Thank you @steve99... :thanks: I figured it was just the quick throttle movements from rev matching and what not but your explanation gives me the insight I need.

You wouldn't happen to have a base map for any turbo kit would you? I'd love to expand my knowledge to the FI world of tuning because one day when im not a broke college student i'll be somewhat ready take on the challenge :paddle:

base maps for sbd turbo kits, you must use exact kit to use maps


http://www.ft86club.com/forums/showp...21&postcount=1

wow i had to many files opened on rom raider.... it works thank you.