Results 1 to 5 of 5

Thread: underspeed overspeed

  1. #1
    Advanced Tuner
    Join Date
    Sep 2013
    Posts
    427

    underspeed overspeed

    tuning cam ls1 I have halved both tables to suit idle etc....good move cause idle is very stable and doesn't hunt at all....sounds good for 232/234 but me mate (owner) wants more of a chop....really good idle at 725rpm/ 18*spark idle ...what do you fellas normally run with your underspeed/overspeed tables...leave them at stock levels or a tad lesser? stock tables were underspeed- 9/9/9/9/9/9/9/7/3/0.00 .....overspeed- 0.0/-2/-6/-9/-9/-9/-9/-11/-14/-16......aqnd then I have reduced them by 50%, any feedback would be greatly appreciated ..... I know I could say drop spark timing at idle/park to 15* and drop idle to say 695rpm....cheers Bret
    Last edited by THE CHAD; 02-20-2014 at 02:26 AM.

  2. #2
    Advanced Tuner VodeAn's Avatar
    Join Date
    Jun 2012
    Posts
    230
    Stock tables are usually too aggressive and lowering them can give you a smoother idle.

    If you're looking for a chop you can try a few things, more aggressive under/overspeed tables, add fuel at idle (use MAF, VE, closed loop ratio...), play with IAC settings in idle airflow.

    Or, put a bigger cam in. I don't like to purposely make a car sound more "cammed" myself but I've have requests from customers a few times.

  3. #3
    Senior Tuner S2H's Avatar
    Join Date
    Apr 2005
    Location
    Schexnayder Racing - Arnaudville LA
    Posts
    4,387
    Quote Originally Posted by VodeAn View Post
    Stock tables are usually too aggressive and lowering them can give you a smoother idle.

    If you're looking for a chop you can try a few things, more aggressive under/overspeed tables, add fuel at idle (use MAF, VE, closed loop ratio...), play with IAC settings in idle airflow.

    Or, put a bigger cam in. I don't like to purposely make a car sound more "cammed" myself but I've have requests from customers a few times.

    stock tables are usually just fine...if they are causing issues, then you have issues somewhere else in the tune.

    one thing I do on very aggressive cams is to take the underspeed tables and make sure its progressive like the overspeed table is
    you should also make sure your idle spark tables and main spark tables match in the area your car idles at
    and typically you want a steady value in the cells around the spot your engine idles at.

    you dont want the idle speed tables too low or you risk issues with coming from higher RPM's back down causing an overshoot and making it stall
    the bigger the cam, and the higher the overlap, the higher the idle needs to be
    a 232/234 cam can idle at 650...but its just stupid to put it there.. it will be much happier with an idle around 850 or 900

    your VE table in that area will also give you a good indicator of whether it can idle at a given RPM... there a point where volumetric efficiency is too low for a stable idle...and at that point you need to just raise it to a higher rpm.
    -Scott -

  4. #4
    Advanced Tuner VodeAn's Avatar
    Join Date
    Jun 2012
    Posts
    230
    I have found that making the underspeed and overspeed less aggressive stops idle from jumping around as much, with everything else nailed down.

    I think I have some data on this, if I find it I'll post it so you don't think I'm throwing poop at the wall. I know I have after logs but need to find some befores...

  5. #5
    Advanced Tuner
    Join Date
    Sep 2013
    Posts
    427
    thanks boys, lowered stock underspeed/overspeed by about 40% idles really good at 800rpm raised it by about 75rpm than previous set up and VE table spot on....sounds nice and mate is happy as larry....VodeAn if you can find some info would be great mate....cheers Bret