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Thread: Help me tune my timing

  1. #51

    Default Help me tune my timing

    Well, the popping/stuttering out the exhaust during mid-range acceleration has magically returned (well, maybe not magically).

    I fired the car up for a short drive last night and hadn't adjusted my IAC off of 0 at warm idle, so before leaving the house I adjusted it up around 15-20ish (this is within the 10-20 recommendation for a manual transmission). Maybe that's the issue, it did seem more crisp with the IAC at zero (it was just barely zero).

    If that isn't the issue, I may consider removing the fuel pressure damper. I initially installed it due to some mid-range surging/sluggishness it had (this was when my timing curve was all in at 2500). When I added the damper the surging went away, but was replaced by the mid-range popping/stuttering. I think it may be possible that the hesitation/sluggishness I experienced WITHOUT the damper may not exist with the faster timing curve I have now (all in at 1500).

    This post is more in-depth documentation of the adjustments I make than anything, but if anybody sees something I don't, please let me know. At this point I'm thinking it's a combination of timing and fuel tuning that's needed. I may have to bite the bullet down the road and go to a return style fuel system. For now, though, I'm still in the 50-100 mile learning curve, so we'll see how it goes.

  2. #52

    Default Help me tune my timing

    UPDATE: I readjusted the throttle blades to achieve 0 IAC at warm idle. Throttle response is better, but the stuttering/popping is still there. I also tried removing the fuel pressure damper, no dice, that must not have been the issue either.

    The issue occurs near medium throttle in 1st gear and as I roll into the throttle through 2nd gear mostly. I sometimes get a slight pop in third, but it's nearly non-existent in third and fourth gear.

    I wonder if I'm experiencing pump cavitation which is causing a lean spot when I roll into the throttle, thus the lean-like pop in the exhaust and the mild stutter (very similar to the way a carbed motor acts when it's shy on fuel during acceleration). It is awfully hot here in Alabama. I guess a fuel return kit may be in order to even the issue out. I've read where similar issues were resolved with installation of the 2922 kit.

    I guess if it's needing more fuel I could try the perfomance setting again, but it's always run terrible on that profile.

    Any thoughts?

  3. #53

    Default Help me tune my timing

    UPDATE: Well, here's what I found... Apparently I mistook the popping and stuttering to be cavitation causing a lean spot. I went for another ride and diagnostics didn't show any cavitation. This was in mid afternoon heat.

    I got to thinking and realized that since it ran a lot more smoothly with no popping or stuttering on the street/stock cam setting (though it couldn't achieve the proper idle afr), maybe I should lean out the pump squirt instead of fattening it up. I dropped the pump squirt down to 22% from 25% and it seemed to do the trick. Nice and smooth as I roll into the throttle through the gears. No more popping or stuttering. I guess it's better to be lucky than good. I'll update again after more drive time.

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