How would you lower LTFT 5% across the board

[nitrorocket]

There are many ways to do it. I have a car im tuning that pretty much needs the LTFT brought down 5% across the entire range. The entire log map shows LTFT at 4-7% in every cell logged. Would you do MAF adjustments? PE? Or IFR?

AFR is pretty much right where I want it already...

And why?

[swingtan]

AFR's will be correct, because LTFT's are correcting the fuel flow to match the airflow. If LTFT's are adding the same amount across the board, depending on you setup, I'd do the following....


Set IFR to a known good value, if theyr are stock injectors, I'd run the stock FR.
For COS-3 I'd then use A0014 to correct for IAT drift.
Next I'd put it in OL-SD and do an auto VE.
Next I'd put it in OL-MAF and dial in the MAF.
Finally I'd turn the O2's back on and recheck the STFT's


If you wanted to cheat a bit, you could just bump the VE and / or MAF by 5%.

Chances are that if the trims were a lot close previously, then the change in weather may be effecting the fueling and pushing the trims further out.

Simon.

[ringram]

6. Disable LTFT and leave STFT active ;)

[swingtan]

Yes, disabling LTFT's is an option once you are certian you have the rest correct. I haven't run LTFT's for about 2 years..... ( actually, I only just turned the STFT's back on..... )

Simon

[dc_justin]

Question: Does the fuel you're using have 10% ethanol? If so, a stoichiometric AFR value of 14.68 is not accurate and will cause fuel trims to be 4+% high.

[redhardsupra]

what to change depends on why the change needs to happen in the first place. you gotta attribute symptoms to the correct causes.

[Redline Motorsports]

Question: Does the fuel you're using have 10% ethanol? If so, a stoichiometric AFR value of 14.68 is not accurate and will cause fuel trims to be 4+% high.

If it does it will cause this percentage of error. stoich is closer to 14.4 with eth.

Plus the o2's have a solid error of 3-4% anyway.

Howard

[nitrorocket]

Actually the fuel does have "up to 10%" ethenol... Hmmm.

[dc_justin]

If it does it will cause this percentage of error. stoich is closer to 14.4 with eth.

Plus the o2's have a solid error of 3-4% anyway.

Howard

It's closer to 14.13, which, with all other things being equal, would yield a 4% trim when compared to pure gasoline.