I was just curious what a "typical" 996TT (no ECU mods of course) shows for its LTFTs. I checked a 996 GT3, and his LTFTs were both (bank 1/bank 2) in the -3 area.

With my new MAF, I am now sitting around -3 for both banks. Can anyone comment?

Stephen?

 

The range is + or - 25 so you are well within the boundries. Anything over 25 triggers a fault. Sitting at - 3 and having both banks equal is a very very good.

 

I'm familiar with the range... I was wondering what a "typical" 996TT sits at, that's all. Call it an average sample...

Here is my reasoning:

Before I switched out my MAF, my LTFTs were in the +3 to +5 area. However, now that I put in my new MAF, my LTFTs are in the -3 area... When I logged a GT3 recently, both banks were sitting around -2 to -3 as well.

I was just wondering what was the "norm" for a 996TT. Perhaps positive? I doubt, but perhaps. Perhaps negative? We would need to pull some fuel under throttle as turbos typically run slightly rich?.

 

Your long LTFT is a direct relation to the amount of air reported to the computer by the MAF. The new MAF is reporting more air passing it than the old one, so the trims are removing the extra fuel. Normal.

 

I know this as well. What I want to know is: For those of you who look at the long term fuel trims on these cars, what is the "typical" value? Are most negative? Are most positive? Is it a split sample? etc...

 

far too many variables to say waht is average.....I'd say average is 0 and thats why the maps are where they are. As I am sure you already know as well, LTFT will compensate for many inbalances in the fuel delivery system...everything from a lazy injector, clogged screen, improperly gapped plug, faulty pressure regulator, blah blah blah....anything at all that changes the delivery at that pont on the map and resulting o2 reading....including a dirty or inaccurate MAF. they are simply and avarage themselves of polled short term trim values.... my only point is that there are many many variables that go into this average of averages, and I don't think you will come up with anything beyond 0 in a decent size sample pool.

dave w

 

Last time I checked mine, after the MAF was replaced, it was close to zero. I wonder if the long term trim is not near zero if the ECU switches to another fuel map to correct it to near zero.

 

That's what I was wondering in terms of the sample. Thanks.