Fast help please

[rtviper]

I had the car tuned by a local turbo shop. The car was tuned on a dyno and I was told it was hard to do because my boost wouldnt go any lower then 19lbs. Now after 10 dyno pulls and 650 bucks for tuning it runs pretty bad at normal driving speeds. The car will backfire through the intake when cold and at idle it hunts for a steady rpm? It will sometimes die when I give it some gas and will hesitate before it picks up rpms. When trying to start it will try to run but never catch on and kind of stumble and die then I try it again and it will fire off. Makes plenty of power with only 18 degrees of timing he put in the car but these other issues have now krept up. Where should I start It is a stage II car with a heavy duty stock style wastegate hence the 19 lbs boost minumum. When I took the car in to be tuned it was really rich according to the Fast and the smell but the plugs looked great with a light brown. Now with an A/F of 11.0 the plugs are really black?? Thanks

 

[QuickWrench]

It sounds like most of the corrections were probably made to the base fuel and timing maps [which is fine], but the AE, DE, temp correction, and other correction tables weren't really touched. Since they work off of and complement the base tables, they'd have to be adjusted as well. Those tables usually aren't done on the dyno...maybe they're expecting you to follow up with these corrections on your own? Dunno...

 

[rtviper]

Quick thanks. Would the corrections he made impact the areas you mentioned as these new problems were not apparent before the tune. Maybe he started with his own program since he used his computer and his O2 sensor tied to his dyno? I am going to download the new program today from the Fast and see whats in there.

 

[Otto J]

datalog things when there happening,send the gct file and datalog and ill take a look

 

[HighPSI]

What kind of dyno was used? I have seen turbo cars tuned on inertia dyno's, that required much more fuel when run on the street.

 

[rtviper]

Cal this was a dynojet model.

 

[QuickWrench]

Quick thanks. Would the corrections he made impact the areas you mentioned as these new problems were not apparent before the tune...

Yes. The correction tables are used by the master algorithm in the ECU as factors against the base tables. For example, if the base fuel map calls for X% of injector duty cycle at a given RPM/Load point, the AE table gives Y% more fuel when factored in [when you stab the throttle]. It's a bit confusing at first.

Due to their nature, it's difficult to adjust the supplementary tables on the dyno. You mentioned that you made 10 pulls, which leads me to believe that the tuner just went after the base tables. That's not uncommon. As Cal stated, the type of dyno makes a huge difference. Any adjustments to the base tables will throw off the correction tables big time.