so i was looking at my data list yesterday and i noticed that my LTFT at idle is -21% when you put a load on it it will bump up to about -8%. does anyone know if this is normal? from what i know your your LTFT is what matters over STFT if you have - #'s the computer is taking away fuel and +#'s is adding fuel. so if i have -21% its laking away fuel. so on my AEM FIC in that cell on my map i put in -20% to offset what the factory computer is doing, right. but the LTFT on the pcm did not change at all. any suggestions. any comments from shifted?
We need to know what engine and mods you are working on. You won't be able to change the AFR in closed loop effectively unless you've changed your PE enable settings. If you are woking on the ecotec platform, it will stay in closed loop up to 6200RPM on the stock calibration. The LTFT at idle is not too important because once it hits a given coolant temp, it will go closed loop. Personally I change the OL&CL settings so that its goes into closed loop quicker, and just take it easy on the throttle until its warmed up.
As far as -8% with load, thats not too bad. Its just saying that over time the PCM has learned that that cell in the VE table is about 8% too rich, so its pulling that much fuel from the value calculated in that cell. The STFT take care of the day to day differences. You'll need HPT and a wideband adjust AFR's properly, and at that point you can only adjust the PE AFRs...
its a 98 2.4. it has an aem intake, pacetter header, and exhaust. i'm currently not working with hp tuneres. any chance you know at what rpm, map or tps % that the pcm goes into open loop at normal operating temps? weather permitting im waiting on installing my aem wide band and connect in to my aem fic.
You can look in HPT to see what rpm and tps it goes into open loop.
i do not have hpt nor do i plan on getting it. it was a question does anyone know what rpm tps% or map at normal operating conditions does it go into open loop?
Since I'm not sure what kind of car you're trying to do this on, that question is hard to answer...
Eco's have a really strict set of parameters before it goes into open loop. LD9's are a bit looser, but it depends pretty much TPS and RPM.
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its a 98 2.4 ld9 cavy 5sp. do you know how the LTFT works on it?
LTFT... Long Term Fuel Trim
What happens is while your car is running in closed loop, it is adjusting two different fuel "trims". These trims are adjustments to the fuel delivered, basically on-the-fly adjustments to the VE table. Your car adjusts the STFT or Short Term Fuel Trim as you are driving along. If the ECU see's that the STFT is consistently high or low, it will add some percentage of that trim to the LTFT. Your STFT's are adjustments after the ECU calculates the needed fuel based on stock VE tables (and some other adjustments), and after it applies the current LTFT.
I wouldn't worry too much about your LTFT at idle, just worry about getting the car to idle comfortably.
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sounds like just your VE tables need a bit of work
1989 Turbo Trans Am #82, 2007 Cobalt SS G85