Results 1 to 5 of 5

Thread: Symptons of incorrect cam timing? Tuning issues with a car way down on power inside

  1. #1

    Symptons of incorrect cam timing? Tuning issues with a car way down on power inside

    If you have tuned a car that was later confirmed to have an incorrect camshaft, sprockets, or was simply installed 'a tooth off' what were the symptoms during tuning?

    I've got a car here that we tuned about a year ago that had our stage 2 torque max camshaft in an LS1 with a set of PRC 5.3 heads. It made 424 rwhp and 403 rwtq which was respectable for the combo.

    Now the same car is back, but with an LQ4 bottom end and our torque max stage 3 camshaft. Same heads, intake, exhaust, etc. Nothing changed but the bottom end and the camshaft to a slightly larger one.

    Now the car is dyno'ing between 395-400 rwhp and around 370 tq. When tuned via the maf or in SD there is a huge lean spike initially then it goes super rich. If tuned to correct this, the maf curve and ve tables look all out of wack.... Even though I try to correct it, it really never irons out. Fuel pressure doesn't drop excessively or anything like that during the hit; it is pretty stable throughout the entire run.

    I checked the cranking compression and 7 out of 8 cylinders had between 180 and 190. One odd ball cylinder checked 220! 180 would probably be on the high side of what I would expect for a relatively low compression engine and a camshaft that has around 20 degrees of overlap.

    Any thoughts on this being a cam timing issue or possibly anything else?
    Attached Files Attached Files

  2. #2
    Advanced Tuner Pulse_GTO's Avatar
    Join Date
    Apr 2008
    Posts
    329
    The only experience I have is a GTO that should have dynoed around 400hp at the wheels did around 320hp. The cam was a tooth off. Fortunately there was no P to V contract.

  3. #3
    Was it difficult to dial in the ve or maf table at wot? Did the car have any drivability issues or idling issues?

    After posting this I spoke with the customer some more about the combo. It seems he purchased the cam second hand from someone else who purchased it on ebay for $220. That would lead me to believe that it may not even be the cam we think it is. Either way, the kpa vs idle rpm seems about right and it has a nice exhaust note so who knows. Drivability is fine.

    Thanks

  4. #4
    i'd say if the cam is installed incorrectly and you have a dyno sheet, the power should be shifted one way or the other fairly dramatically from where it should be. if cam is retarded one tooth it will be lazy and advanced one tooth it will come in early and die off hard up top. it's possible that the cam is installed correctly and simply not the correct cam. a degree wheel would be the proper indication.
    AAHHHHH!!!!!!

  5. #5
    only guessing here, as I can't see your fuel pressure or AFR-but it seems like your injector duty cycle is a bit on the high side for a car making only 400 whp with the injector flow rate in your tunefile. are you sure your dyno data is accurate? beyond that-i'd agree with tramotorsports, should be a shift in power delivery, as well as possibly being a bit lazy or unwilling to run out the top....