GTM Motorsports Oil Cooler

Denny McLain · 09-13-2009, 07:58 AM

[QUOTE=Modshack;195852]Understand...When I saw how limited the Cobb was I decided that was $6-700 I didn't need to spend...at least now.

I've been tuning my A/F ratios with changes in my MAF tube diameters. I think I have it pretty much set now...Long term fuel trims are still at "0" correction after almost 200 miles..

QUOTE]

Very interesting concept however an issue I see is the factory fuel curve is not linear. The same progression on every wideband readout I've seen. The cars are leaner at lower rpm getting progressively richer at higher rpm's.

Mine's pulling out additional timing beginning right at 5000 rpm (as low as 17 and 18 degrees timing) which is killing the torque peak. In looking at the dyno wideband readouts, Cobbs AFR readouts (which aren't accurate btw), discussing this with Calvin At Cobb whom originally tuned the car, it appears the car might be a little lean under 5000 rpm which may be causing it to pull timing. It also might be the temps? Added fuel under 5000 and pulled some over 7000. (which shows 25-27 degrees of timing depending upon the temps) To do true fine tuning, you need to get into the MAF tables and hone on specific rpm's with the Cobb software as the fuel tables are pretty course.

Biggest tuning issue and something I've never run into is when you make changes to AFR, you see it on the 02 readouts, but the car does not immediately respond on the dyno. This is a tremendous source of frustration as it's a place I've never been before, don't know why or what to do about it.

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09-13-2009, 07:58 AM	#28 (permalink)
Denny McLain Enthusiast Member Join Date: Feb 2009 Location: Double Oak Tx Posts: 255 Drives: 370Z, 96CE hotrod Rep Power: 18	[QUOTE=Modshack;195852]Understand...When I saw how limited the Cobb was I decided that was $6-700 I didn't need to spend...at least now. I've been tuning my A/F ratios with changes in my MAF tube diameters. I think I have it pretty much set now...Long term fuel trims are still at "0" correction after almost 200 miles.. QUOTE] Very interesting concept however an issue I see is the factory fuel curve is not linear. The same progression on every wideband readout I've seen. The cars are leaner at lower rpm getting progressively richer at higher rpm's. Mine's pulling out additional timing beginning right at 5000 rpm (as low as 17 and 18 degrees timing) which is killing the torque peak. In looking at the dyno wideband readouts, Cobbs AFR readouts (which aren't accurate btw), discussing this with Calvin At Cobb whom originally tuned the car, it appears the car might be a little lean under 5000 rpm which may be causing it to pull timing. It also might be the temps? Added fuel under 5000 and pulled some over 7000. (which shows 25-27 degrees of timing depending upon the temps) To do true fine tuning, you need to get into the MAF tables and hone on specific rpm's with the Cobb software as the fuel tables are pretty course. Biggest tuning issue and something I've never run into is when you make changes to AFR, you see it on the 02 readouts, but the car does not immediately respond on the dyno. This is a tremendous source of frustration as it's a place I've never been before, don't know why or what to do about it.