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N40GL
01-23-2008, 10:48 AM
Here's one for all the experts here.

Background

I've got KB #10, and I've upgraded to a Cobra long block (cast iron, forged internals) onto which the Marauder heads are installed. Because the Cobra long block was only 8.5:1 compression (instead of the normal 10.0:1) I upgraded to a Vortech T2SQ pushing 14 psi to make up the difference in performance. Of course, this required an upgrade to the blow-off valve (now a Vortech "Mondo"), and an upgrade to an SCT 90MM MAF (model may be 2850 - it's not the 2600).

Perhaps most important for me was to keep Kenny Brown's original design for all the plumbing intact. I know there have been lots of discussions regarding the merits of a "push through" vs. a "suck through" system (i.e. where to put the MAF); let's set that aside in this discussion. If the car is going to keep its value, my opinion is that it needs to be as close to the way Kenny designed it as possible. That's why it isn't changed.

At the end of the day, it runs great, and dyno'ed about a year ago at 460HP at the rear wheels. It may have more in it, but I still want to drive it, so I'm not searching for the last ounce of performance.

Issue

At very low throttle input, I can stall the car pretty easily. For example - let's say I'm sitting in traffic waiting to make a left turn, and the car in front of me moves up. If I goose the throttle just enough to close the gap, I can stall the engine. Almost everybody attributes this to the 90MM MAF, and the fact that its confusing the ECU. Usually a bit easier to stall it when its cold, but then it'll do it when it's warmed up as well.

No chip - tuned and loaded into the ECU with the Xcalibrator.

This is really the only thing in an otherwise perfect car (IMHO).

The Question

Has anyone developed a solution to this annoyance? It will probably take a dyno trip to do it, and that's fine (within reason - I ain't gonna drive it to California from Virginia!). I'd sure be interested in hearing what people have learned over the past 4 years.

Mark

(No - I'm not changing the plumbing, even if I can put it back the way it was. See above.)

magindat
01-23-2008, 10:58 AM
My first guess would be to look for a vacuum leak after the charger.

BTW, if you DO have a vac leak after the charger, you also have a boost leak. If you DO have a leak at all, you'll likely need a retune cuz you'll have more air under boost and run lean.

I've been having similar issues with mine in as much as it sometimes won't stay started when warm. I found some leaks and closed 'em up, but now have a tiny bit of detonation in the 4500-5500 band, so I know I'm getting more air and leaning out a bit. Once I think I have the leak solution 100%, I'll turn down the AF on the Xcal and reflash.

Zack
01-23-2008, 11:08 AM
A simple adjustment to the Idle Air Transfer Function and the stalling will go away.
I have the value file at home if you need it.

Zack
01-23-2008, 11:11 AM
Also, if you want to maintain the stock appearance, you can install a 05+ Mustang GT maf in the stock meter (underneath and no one would ever know.)