Does heat soak cause negative fuel trims?
Thread Starter
Safety Car
Joined: Nov 2007
Posts: 4,436
Likes: 875
From: Bay Area CA
Does heat soak cause negative fuel trims?
After driving a couple of hours my fuel trims read -3 to -14. Normally, they are within + or - 6. The ECT is 195* and IAT 50*. What causes my fuel trims to remain negative after a couple hour drive. What exactly is heat soak? Can heat soak effect fuel trims. Thanks for any responses.
Just to add:
On one scan reading both STFT and LTFT were reading -12, -14 on both banks, then settles down to single negative digits and back to double negative digits.
The CAT Temps were 1166 and 1216 F.
OEM Tune!
This occurs with both an aftermarket CAI and stock air intake.
Just to add:
On one scan reading both STFT and LTFT were reading -12, -14 on both banks, then settles down to single negative digits and back to double negative digits.
The CAT Temps were 1166 and 1216 F.
OEM Tune!
This occurs with both an aftermarket CAI and stock air intake.
Last edited by Mike's LS3; Jan 11, 2012 at 11:06 AM.
Melting Slicks
Joined: Dec 2011
Posts: 2,690
Likes: 116
From: Richmond area Va
heat soak is when the engine temperature creeps up into the intake components / heating the incomming air prior to entering the head.
iat sensor reading can potentially have nothing to do with reading heat soak, especially in a c6 application where it is far from the intake mani. while i like my iat's mounted in the intak manifold, seems like oem's prefer to stick it way up front, more of an AMBIENT air temp sensor vs. INTAKE.. but what do they know hah.
far as your trims are concerned. as things heat up, the air entering the engine heats up, and thins out (less dense, less oxygen) to keep the a/f even with less oxygen, the computer removes fuel, hence the further negative values.
that being said it should be *mostly* forseen by whoever put the tune in the car, and the warm up fueling calibrated to account for it, far as iat location, it all comes out in the wash.
iat sensor reading can potentially have nothing to do with reading heat soak, especially in a c6 application where it is far from the intake mani. while i like my iat's mounted in the intak manifold, seems like oem's prefer to stick it way up front, more of an AMBIENT air temp sensor vs. INTAKE.. but what do they know hah.
far as your trims are concerned. as things heat up, the air entering the engine heats up, and thins out (less dense, less oxygen) to keep the a/f even with less oxygen, the computer removes fuel, hence the further negative values.
that being said it should be *mostly* forseen by whoever put the tune in the car, and the warm up fueling calibrated to account for it, far as iat location, it all comes out in the wash.
Thread Starter
Safety Car
Joined: Nov 2007
Posts: 4,436
Likes: 875
From: Bay Area CA
Thread Starter
Safety Car
Joined: Nov 2007
Posts: 4,436
Likes: 875
From: Bay Area CA
heat soak is when the engine temperature creeps up into the intake components / heating the incomming air prior to entering the head.
iat sensor reading can potentially have nothing to do with reading heat soak, especially in a c6 application where it is far from the intake mani. while i like my iat's mounted in the intak manifold, seems like oem's prefer to stick it way up front, more of an AMBIENT air temp sensor vs. INTAKE.. but what do they know hah.
far as your trims are concerned. as things heat up, the air entering the engine heats up, and thins out (less dense, less oxygen) to keep the a/f even with less oxygen, the computer removes fuel, hence the further negative values.
that being said it should be *mostly* forseen by whoever put the tune in the car, and the warm up fueling calibrated to account for it, far as iat location, it all comes out in the wash.
iat sensor reading can potentially have nothing to do with reading heat soak, especially in a c6 application where it is far from the intake mani. while i like my iat's mounted in the intak manifold, seems like oem's prefer to stick it way up front, more of an AMBIENT air temp sensor vs. INTAKE.. but what do they know hah.
far as your trims are concerned. as things heat up, the air entering the engine heats up, and thins out (less dense, less oxygen) to keep the a/f even with less oxygen, the computer removes fuel, hence the further negative values.
that being said it should be *mostly* forseen by whoever put the tune in the car, and the warm up fueling calibrated to account for it, far as iat location, it all comes out in the wash.
