Thread: tuning help
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Old 06-12-2010, 09:25 AM   #14
AaronGTR
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AKA: Aaron
Join Date: Aug 2002
Location: Detroit area, MI
Age: 39
Posts: 12,197
Vehicle: 2000 Grand Am GT1 2dr
AaronGTR has made plenty of valid pointsAaronGTR has made plenty of valid points
Stock fuel pressure on the 2000 GA is 48psi and 55psi WOT. I would be highly surprised if you got to 60psi while not in boost yet. You can run a little higher or lower pressure at idle, but you need to adjust the value in your IFR table then since the injector flow rate changes with pressure. Yes, the pcm will adjust for that on it's own a little with fuel trims, but you really should try and adjust for it some yourself to keep fuel trims inline. I think 46-48psi at idle is a good spot to be at.

What are you using in your IFR table? I know the DHP tuner has some pre-made files in the import folder for IFR tables for different injector sizes. My experience has been that they will get you close, but they aren't quite perfect. They were setup for grand prixs and not optimized on grand ams.

I'm running the same injectors with a caspers AFPR set at 48psi at 14 In/Hg of vacuum at 800rpm at idle. My IFR table is 228 across the board, slightly richer than the DHP scale. Give those a try and see how it works. It sounds to me though like your numbers shouldn't be that far off where you should be, so if the car is running that bad I wonder if there is some other problem? Well, try that first and let us know how it works.
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