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Sep 30, 2008 | 11:43 AM

#26

Maven

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Joined: 05-25-05

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From: Southern New Jersey

Quote:

Originally Posted by jlong3382

Factory tunes are so general that the ecm will pull timing (even if its only a fraction of a degree) no matter what pump gas you run. Factory tunes are designed to work in alomost all climate conditions. For example: Lets take the wonderful climate here in northern Indiana. 95 Degrees on a hot summer day, - 10 degrees on a clod winter night winter. The factory tune has to work in both situations. The computer adds/subtracts timing wherever it feels is needed to maintain low/no knock condition while achieving driveable performance. It uses the good spark timing table as a guide. If your wondering how I know this, I did my own tuning in my Grand Prix for almost 3 years. I'm not a professional but I know how an ecm works and I've done a lot of research.

I am well aware of this. And what I have been stating is that the ECM isnt pulling "a fraction of a degree" its using as much a -5 degrees on nearly new cars running the minimum 87 octqane fuel from a TopTier fule supplier as GM recommends.

If I had only ever seen -1's, I wouldnt be concerned, the ECM will go -1 while your floating down the highway, My point is that I am not talking about -1, or -2 degrees of timing, I am talking -3, -4, -5, consistently and and on several occasions and with several vehicles even as much as a -9 adjustment on properly running cars.

Reducing the timing advance by 5 degrees under full load is unacceptable, and this is what happens when you run 87 in a 2.2L.
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You know, what? I fold, you guys are right, I dont know what the hell I am talking about. I am gonna fill my car with some fresh 87 octane fuel and head over to get it fixed at the dealer, theres gotto be someone there who could fix it.

Last edited by Maven; Sep 30, 2008 at 11:51 AM. Reason: Automerged Doublepost

Sep 30, 2008 | 04:05 PM

#27

jlong3382

Senior Member

Joined: 02-09-08

Posts: 1,607

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From: Indiana

I was agreeing with you Maven

But I had no idea an ecotech pulled 5 degrees going down the road. wow. it wasn't that way with my 3800; of course I tuned it so many times that i forget what the factory number were