|
Originally posted by lickscissors
turbo, built engine..blah, blah...anyways i want to retard the ignition to be on the safe side of detonation...oh yeah, im at custom je 9.6 pistons.... anyways, i have a msd dis2...whats a good value to start with... any help..thanks doug
Well, exactly how much ignition timing you will have to pull out is kind of a guess and check.
Are you going to try to see how much power you can make on 93 octane?
Are you going to be doing it Home Depot style by mixing in xylene to see how much you can stretch it without leaded gas?
Or do you want to just run C16?
For a xylene mix (like dumping in 1 gallon when you have about 1/2 of a tank, seems to work the best for me, lets me run about 1.3-1.4 bar on stock timing, if I don't add any xylene I can get 1.1 bar on a good day) or pump gas, you will have to figure out how much retard you need on your own, you will probably need a MSD knock alert (XtremeRS has one, saw it at the Shootout, it's pretty cool) in order to figure out exactly when you start to detonate and how effective pulling out X degrees per Y PSI of boost is. I've found that the upper limit for my setup (8.8:1 pistons, 93 octane, 11.5-12.0:1 AFR, ~20 degrees of advance) seems to be about 1.0-1.1 bar of boost. I haven't really played with my MSD unit much at all, I'd rather run a little less boost on a more advanced timing curve, but these days I've though about retarding the timing a little so I can get closer to the peak efficiency of the 16G in order to supply enough airflow for these cams... But anyways...
If you're going to run C16 at all, you probably will want to leave the timing alone.
If you just HAVE to get a number so you can go out an try it, start off with 3 degrees of timing pulled back for every 15 PSI of boost. I just pulled that number out of my ass, give it a try, see what happens. If you think that you're loosing a bit more power than you'd like and your EGT's are higher than they should be, try to lower the number a little until you start to hear detonation, then raise it a little to give yourself a little saftey margin.
2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)
|
Search
Printer-friendly copy
1 User in Chat
