How negative is to negative dealing with LTrims???
Thread Starter
Joined: Aug 2002
Posts: 10,331
Likes: 1
From: San Antonio, TX
How negative is to negative dealing with LTrims??? The reason i ask is because i have been monitering my new motor with A-tap and at idle my LTrims are -1.6, left and right bank. Now under med. throttle ie 2k- 2.5k my LTrims are -14.9 This is a brand new motor with 80 miles on it and i want the rings to seat right and i was told if theres to much left over gas in the cylinder then it would wash most of the oil away and the rings would not seat right. Are my LTrims to negative ie to rich, to much fuel???? Thanks
Kyle
Kyle
-25% is the PCM's control limit for LTFTs, if it can't
get happy by this point it will set codes. The trims
mean though that by pulling this amount the PCM
has made things dead balanced, so there's no "fuel
wash" going on (closed loop). However it indicates
the fundamental air metering or fuel shot is off by
15% (fat) just when things are starting to get
interesting, maybe more higher up. If this LTFT is
still "creeping" you may end up past the comp limit.
If it's stable then you have some time to get tuned,
swap back to stock-tune-consistent injectors, or
whatever.
get happy by this point it will set codes. The trims
mean though that by pulling this amount the PCM
has made things dead balanced, so there's no "fuel
wash" going on (closed loop). However it indicates
the fundamental air metering or fuel shot is off by
15% (fat) just when things are starting to get
interesting, maybe more higher up. If this LTFT is
still "creeping" you may end up past the comp limit.
If it's stable then you have some time to get tuned,
swap back to stock-tune-consistent injectors, or
whatever.
Thread Starter
Joined: Aug 2002
Posts: 10,331
Likes: 1
From: San Antonio, TX
They just rise from idle and dont go over -14.9........... this is with Motron 60# Injectors and a 9:1 iron block 370 all motor........ Jayson at MTI tried to get them close as possible... mail order for new motor to break it in before i drove it to Houston to tune the new motor with boost...... Would it help to back off my fuel pressure?? I have a adjustable reg. and its set at 57-58 psi right now.....
Thanks
Kyle
Thanks
Kyle
My take is, the injector flow needs tweaked for the
midband (scale *1.15) and then the offset to true
up any near-idle residual error. You could get the
same effect by dropping pressure by about 30%
but that's not really how you want to run around
I think.
midband (scale *1.15) and then the offset to true
up any near-idle residual error. You could get the
same effect by dropping pressure by about 30%
but that's not really how you want to run around
I think.
