3.7L vs 3.5L programming differences
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3.7L vs 3.5L programming differences - 4/7/2007 10:26:48 PM
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ChevyHighPerformance
Posts: 159
Joined: 7/5/2006
Status: offline
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I was asked about the differences between the programming for the 3.7L and the 3.5L. This may not mean anything to some of you, but here are the major differences in PCM programming between the 3.5L and 3.7L (auto tranny):
1) The 3.7L has a little higher idle in gear when cold and high temps (241F and over).
2) The MAF calibration table is about 8% higher, but the 3.7L has a new MAF.
3) The VE tables are different (as expected with a slightly different displacement). The low, mid, and high cam threshold angles are a little higher with the 3.7L.
4) The deceleration fuel cutoff is disabled for 3rd and 4th gears with the 3.7L. For my tuning, I only disabled the DFCO cutoff in 4th gear. Sometimes when going down a hill, I’ll put the tranny in 3rd and let the compression slow me down instead of riding the brakes, and the DFCO in 3rd helps.
5) Open loop A/F is a little different.
6) Closed loop enable is much quicker with the 3.7L. The closed loop delay time is now zero.
7) The WOT A/F is a little leaner with the 3.7L.
8) The lowest COT temperature threshold is 9F higher with the 3.7L.
9) The high octane timing table is generally higher with the 3.7L with the exception at low RPMs (idle and lower).
10) IAT timing adder pulls out about 1 degree more timing above 176F with the 3.7L.
11) The cat lightoff is a little different.
12) The 3.7L has lower burst knock retard (base vs CylairDelta).
13) The ETC max vs RPM vs Max torque is less restrictive with the 3.7L.
14) The tranny shifts to a higher gear for lower TPS’s with the 3.7L. I’m guessing this was done to try and improve MPG with the higher torque 3.7L.
15) The 1->2 and the 2->3 shifts are softer with the 3.7L.
16) The torque converter locks at lower speeds with the 3.7L.
17) The torque reduction during shifts is less with the 3.7L.
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