kTuner STFT/LTFT tuning

[d1zguy]

Hi All,

After a while I was able to get my STFT values within +- 3% on a stock MAF. On my particular car LTFT's were 7% at idle and lowered to about 3.54% on the highway.

I used

http://vimsh.github.io/mafscaling/

Got in touch with the developer and was able to use the tool on Maf.Hz cars. Which my SI is. EX-T's and others use a Maf.v style maf and the tool will work out of the get go. The tool will be more useful for those that want to use a larger MAF housing, etc.




Recommended way to tune is to turn off LTFT's by settings LTFT fields in ktuner to 0%. Then logging and entering in the parameters on the tool. I was having a hard time scaling the upper end of the scale as I was not collecting enough data points but the trims were about 3-4 percent.

I ended up scaling the entire curve by 5.34% and that got me within +-3% 0-5 is the best we can aim for.

Misc:

Looking at logs it looks like the SI is always in closed loop showing Fuel_Status 2 under the logs for OL. This may be different on EX-T cars.

In addition it's best to just turn off LTFT's. The LTFT strategy on these ECU's is not the same as others and results in running too rich when the AFR is actually okay. i.e idle for too long at 8% STFT will make the LTFT increase to 8%. Then cruise at 45mph in 5th gear and stft will show 3% but will still be too rich at 8%. and will be running 5% richer than it should be until it cruises for longer at 3% and goes back down.

Short Term Fuel Trim (STFT): is an additive correction % the ECM is using to actively modify the injector pulse-width based on lamda correction (requested vs. actual) at idle and very light load. Once recorded fuel trims pass a preprogrammed threshold the LTFT is increased and the STFT cycle is reset and continues to recalculate based on the newly configured LTFT.

Long Term Fuel Trim (LTFT): is a multiplicative % calculated into the injector pulse width. LTFT trims are factored across the whole spectrum of engine operation increasing with relationship to engine load.

 

[choo]

Thats a good tip to set the max trim to 0. It probably would have been easier lol.

I only really needed to adjust the lower airflow area up to light throttle on my car, afterwards it seems to stay around 2-3% as well.

From the factory I was seeing 10% trims, and idle quality was poor. It was idling at 620 when targeting 700.

 

[d1zguy]

Thats a good tip to set the max trim to 0. It probably would have been easier lol.

I only really needed to adjust the lower airflow area up to light throttle on my car, afterwards it seems to stay around 2-3% as well.

From the factory I was seeing 10% trims, and idle quality was poor. It was idling at 620 when targeting 700.

You can actually run without any LTFT correction. I would suggest increasing the idle speed, keeps a higher oil pressure. I am running 900 when I go to the track to keep the fluid moving while cooling down after a session for everyday I just set it to 800

 

[Cscott_xGen]

Should i be worried about this on a stage 1 vit tune?

 

[davemarco]

Not unless you're using a larger MAF housing on your intake.

 

[CIVICUK]

You can actually run without any LTFT correction. I would suggest increasing the idle speed, keeps a higher oil pressure. I am running 900 when I go to the track to keep the fluid moving while cooling down after a session for everyday I just set it to 800

have you adjusted the post start idle by any chance? on cold starts with the Greddy catbck and prl dp/fp its insane because it targets 1500rpm until it reaches 60 degrees so i have always wondered if it is safe to lower post start idles

 

[fenix-silver]

have you adjusted the post start idle by any chance? on cold starts with the Greddy catbck and prl dp/fp its insane because it targets 1500rpm until it reaches 60 degrees so i have always wondered if it is safe to lower post start idles

That seems excessive. No harm in lowering your idle. You'll know if you lower it too much since it won't idle well.

 

[CIVICUK]

That seems excessive. No harm in lowering your idle. You'll know if you lower it too much since it won't idle well.

Thank you for confirming that! Yes i agree it is excessive for a cold start idle, i have had to go down the root of adding an extra resonator because ktuner says they have not changed anything of idle targets and that is what honda has set it set to from factory. It seems the eu/uk 1.5 engines are set up differently from the US.

By the way i was having trouble not getting my stft to read close to zero after numerous datalogs and adjusting maf scale it just would not get lower so i took your advice on increasing the idle so i changed mine from 720 to 800rpm and its helped a lot! i dont supose you have tuned your ignition and timing also? Im trying to figure out if theres any improvement to be made on mine.

Sorry for all the questions!

 

[Christianjwong]

what is a good stft w/prl race maf to stay around

 

[fenix-silver]

what is a good stft w/prl race maf to stay around

stft is always all over the place, especially as the load varies. As long as you aren't seeing much more than +/-25 and during steady state it is single digits, you should be good. Ltft should be with +/-10

 

[Christianjwong]

stft is always all over the place, especially as the load varies. As long as you aren't seeing much more than +/-25 and during steady state it is single digits, you should be good. Ltft should be with +/-10

Okay good bc I think the most I've seen is +/-7

 

[Stormtachi160]

Hi All,

After a while I was able to get my STFT values within +- 3% on a stock MAF. On my particular car LTFT's were 7% at idle and lowered to about 3.54% on the highway.

I used

http://vimsh.github.io/mafscaling/

Got in touch with the developer and was able to use the tool on Maf.Hz cars. Which my SI is. EX-T's and others use a Maf.v style maf and the tool will work out of the get go. The tool will be more useful for those that want to use a larger MAF housing, etc.




Recommended way to tune is to turn off LTFT's by settings LTFT fields in ktuner to 0%. Then logging and entering in the parameters on the tool. I was having a hard time scaling the upper end of the scale as I was not collecting enough data points but the trims were about 3-4 percent.

I ended up scaling the entire curve by 5.34% and that got me within +-3% 0-5 is the best we can aim for.

Misc:

Looking at logs it looks like the SI is always in closed loop showing Fuel_Status 2 under the logs for OL. This may be different on EX-T cars.

In addition it's best to just turn off LTFT's. The LTFT strategy on these ECU's is not the same as others and results in running too rich when the AFR is actually okay. i.e idle for too long at 8% STFT will make the LTFT increase to 8%. Then cruise at 45mph in 5th gear and stft will show 3% but will still be too rich at 8%. and will be running 5% richer than it should be until it cruises for longer at 3% and goes back down.

Short Term Fuel Trim (STFT): is an additive correction % the ECM is using to actively modify the injector pulse-width based on lamda correction (requested vs. actual) at idle and very light load. Once recorded fuel trims pass a preprogrammed threshold the LTFT is increased and the STFT cycle is reset and continues to recalculate based on the newly configured LTFT.

Long Term Fuel Trim (LTFT): is a multiplicative % calculated into the injector pulse width. LTFT trims are factored across the whole spectrum of engine operation increasing with relationship to engine load.

Who do I go to if I need help getting the software to work for me?