BrianGallimore

Newbie question:

Why did my LTFT histogram increase (most cells went to ~10) when I re-enabled the MAF, after tuning in SD mode?

I had identical low and high octane spark tables while monitoring LTFT and changing the VE table. I had the VE table pretty much set (most LTFT near 0), then re-enabled the MAF. When I did, I seem to get more power, but my trims are now off.

My first thought is that my MAF needs re-calibrating, but then I realize that both modes are being tuned by the O2 sensors... so that makes me think something else is going on... like the engine is "allowed" to produce more power in MAF mode, and is calling for more fuel. (this might be the case if the spark tables were different... but they are not)

Please give me a clue.

LS1 Sounds

iTrader: (11)

Need to re-cal the MAF table. Check out redhardsupra's MAF calculator spreadsheet, I think it's in the sticky thread.

gtodoug

iTrader: (1)

You need to recalibrate the maf. Your tune may be looking good in SD mode, but the maf is not following the tune. You need to align the two. It is normal for Fuel trims to go positive after reconnecting the maf. The process for recalibrating the maf is a sticky in the top of this forum.

Dougie

RedHardSupra

iTrader: (1)

yup, it's very simple: if you go SD -> MAF and suddenly LTFTs are screwy, your MAF is off. recalibrate maf, go SD->MAF again, and you should see VERY little changes.

BrianGallimore

thanks guys... I missed that step!

I'll get there.