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Thread: SD tune...AFR differences in P/N vs D

  1. 12-22-2006 #1
    Scott125
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    SD tune...AFR differences in P/N vs D

    I've done quite a few SD tunes, but am tuning a pretty big cam...240/249/640/620 on a 112+2, it is real touchy on the AFR. I was noticing in park the AFR was around 14.1...so I was wanting to get it around 14.5. I took some fuel out...landed about right. After that, when I put it into drive, it is leaning out pretty bad....into the 15's. So lean, it causes it to surge. I can fatten it back up to where it runs in the high 13's on P/N and it kills your eyes....but goes to 14.5 in drive. The car is an auto with a 4k stall. I have never seen a car go that lean when the load of the tranny was placed on it....Any suggestions? I figure I'm going to have to find a happy medium between the two, but it would be nice if there were a hidden table somewhere for this I guess this is the down side of a cam that is meant for track use only.

    Thanks
    Scott
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  2. 12-22-2006 #2
    WS6FirebirdTA00
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    What size motor?

    You prob need to mess with the idle settings some to get it in line a little better. Post a log and tune up here.
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  3. 12-23-2006 #3
    EC_Tune
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    How much did the MAP change when pulling it into gear? VE/MAF table(s) may be a bit lean at the in-gear MAP setting.
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  4. 12-23-2006 #4
    Scott125
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    Its a stock 346ci.

    The car idles around 925...in the 800 cell at around 70 MAP. When I move from P to D, it really doesn't move....it may go out to the 1200/70 cells, but comes back.

    Another problem too. Usually when I get one dialed in hot, with a good AFR, timing etc... they cold start pretty good. This thing flat out sucks! Surges too much and just generally sucks..lol. It's definately giving me fits.

    I'll see if I can't post the file...new at that so might not be able to.
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  5. 12-24-2006 #5
    EC_Tune
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    With that much cam you may have to run in Open Loop Speed density to get the result you are after. Cars with a lot of overlap can confuse the o2 sensors as you have a LOT of internal EGR built in with that cam. The exhaust valve looks like a bigger opening than the throttle body at idle.

    I hope you have higher compression (11.75 -12.5:1 would be a minimum) for that cam if you haven't done so already.

    BTW: with that much cam on a 346 I wouldn't let it idle less than 1000 RPM.

    To post your file, click the "Go Advanced button. Then you will see the little paper clip icon show up. That's how you attach your tune/log.

    HTH
    EC
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