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3900 fiero tuning

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  • 3900 fiero tuning

    I have had the 3900 running for a while and recently switched to a 4speed manual. I had it tuned a couple times by different people and after that raised compression with thinner head gaskets and changed up the exhaust a little. I then got an apu1 and started tuning myself. I sent Superdave a copy of the bin and he graciously modified the timing tables for me. The car was still lean and had some hesitations and I worked around that. Now, I'm new to tuning so I went back and added my old spark table but blended it down to superdaves table in the 90-100kpa ranges plus two degrees. I took it out for a drive and the car feels good with no KR. The afr is 12.2:1 at full throttle. So now the question is do I do anything or leave it alone? It seems like leaning it out could add power but I thought I remember reading here that these engines like fuel. Any advise is appreciated on what to do next or call it good and take it to the track.

  • #2
    lean it a bit, push on it, see if it feels better. if it does, do it again, if not, go backwards, or go even richer, see how it feels.
    1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
    Latest nAst1 files here!
    Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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    • #3
      Originally posted by robertisaar View Post
      lean it a bit, push on it, see if it feels better. if it does, do it again, if not, go backwards, or go even richer, see how it feels.
      I dropped the BPC 2 points and took it for a spin. Engine cool the afr was low to mid 13's. As the engine got closer to 180* the afr was back to 12.2. It could be dependent on which gear I was in and if I was full throttle through multiple hears, I don't know. I didn't see anything dangerous afr wise or KR so I think I'll have to leave it and see what it does at the track. Thanks for the help.

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      • #4
        you'll want to change the commanded PE AFR, not by adjusting the BPC, since that effects global fueling, not just PE.
        1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
        Latest nAst1 files here!
        Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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        • #5
          That whole table is set to 12.8.

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          • #6
            if you want more or less fuel only in PE/WOT, that's the table to play with. ideally, that table should match your wideband readings in PE, assuming your target AFR doesn't deviate due to cat overtemp or anything else.
            1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
            Latest nAst1 files here!
            Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

            Comment

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