charcoal03silvy

iTrader: (1)

Been doing some tuning lately on my own truck and on a few friends' trucks. All mostly stock with a few bolt ons.

I know you're supposed to do the VE table first and that its the basis for a good tune. I have my VE dialed in to where my LTFT's are all +-1.5 for the most part. I also have another truck with headers tuned where his LTFT's are +- 2 or 3. The STFT's are a different story. Playing with mine and tuning to where my STFT's are very close, my LTFT's seem to get more off. Truck feels better when the LTFT's are dialed in vs the STFT's being dialed in.

Doing some reading on the web and looking at some tuning guides, it seems people either do STFT's or LTFT's and few do both.

Just looking for opinions on which is the "proper" way to tune the VE without a wideband.

smokeshow

iTrader: (16)

I would disable LTFTs entirely while you are tuning VE and reference STFTs directly. Otherwise you're chasing a moving target. It really depends on what method you'd prefer, as there are several ways to do it.

charcoal03silvy

iTrader: (1)

What exactly do you mean a "moving target?" Reading krambo's tuning guide on here he does it all by LTFT's. Just trying to understand the theory behind the practice

Also have read a guide that says to tune using LTFT's until they're within +- 10, then switch to using STFT's

smokeshow

iTrader: (16)

Exactly what I mean by several ways to do it My point is if you tune via LTFTs and then switch to STFTs, they will be affected by existing LTFTs and will skew your results. The short terms will not be accounting for all of the fueling error, just whatever the long terms haven't already accounted for. That leaves you with an error. I'm sure Krambo covered that in the guide, he probably just worded it differently.

charcoal03silvy

iTrader: (1)

Opinions on enabling LTFT's after STFT's are dialed in? Have also read that a lot of people leave them disabled...

smokeshow

iTrader: (16)

For an NA setup you can re-enable them. Often times with forced induction, throttle transitions can sometimes result in LTFTs learning bad values so its not a bad idea to leave them disabled. I haven't used LTFTs since I ran NA.

AKlowriderZ71

iTrader: (22)

The "proper" way to tune the VE, is with a wideband. Using the narrowbands will get you closer, but it's still a craps shoot IMHO.

As far as fuel trim tuning goes....

I usually get the LTFT close, then go after the STFT. Remember to reset fuel trims after every adjustment you make, or you'll be chasing your tail even worse.

oakley6575

iTrader: (5)

Personally I would disable LTFT and do a lot of STFT driving after you reset the fuel trims. But as far as re-enabling LTFT, I like them off. When I enable closed loop after tuning the VE in open loop, my truck will idle at 14.3 instead of 14.7-15. So I find the VE to be a lot closer driving without stored trims.

slow67

iTrader: (2)

I like to disable LTFTs, as its possible for it to modify WOT fueling (if you were in that Fuel Trim cell long enough for LTFTs to write).

krambo

iTrader: (4)

I need to read what I wrote! LOL! was this in idle tuning? Personally, I do not like LTFT methods of tuning. If you disable LTFT, clear all storred trims and dial in your airmass tables using STFT (several sessions with smoothing), it is MUCH faster and ultimately you will end up with the same result as tuning with LTFT. For the higher portions of the Ve / MAF, you will need a wideband.

Agree. Log AFR error across the entire table (WOT and cruising cells) and be done with it.