dirkdiggler350

So I have been playing with the timing on my Lq4 swapped Iroc, the motor is a iron headed LQ4 with a Performer RPM intake and a set of True Duals other wise its completely stock. It runs much better than when I had the preset chips in it. Part throttle seems much better cant really get into wot because its pretty lean up top I had it on the dyno the other day it made 270hp and 300 lbft with the converter unlocked and a/f at 14.8. Heres where it is as of now. 15° cranking 26° at idle, and 36° all in by 1500 rpm. Map adds 7°. Any feedback would be appreciated, Thanks.

Doug G

You may be just fine after you fatten up the AFR some ?

All stock, I would lower that curve to around 26 + the 7 MAP. Don't need a lot with a stock motor .....and see how it does.

dirkdiggler350

I pulled the jets out 67/75 and put in 70/80. The car deaf pulls much better mid range and up top. it's pretty much dialed in other than a weird surge that it has at idle it jumps around 200 rpm or so, seems like a vacuum leak but I can't figure out from where. I'm gonna try dropping the timing and see how that works.

Doug G

Make sure in the MSD that the idle control is off...if it still surges, maybe try to remove the MAP (make it 0) to see if that changes anything and go from there.

dirkdiggler350

Sure as hell I had the idle control still enabled, turned it off and the surge went away. Question on what you said earlier about the timing, so your saying i should run 26* base +7 from the map but that would still only leave me with 26* at wot that seems kinda low for carbed motor no?

Doug G

Motor doesn't care if FI or carbed....they have very efficient chambers and that's where your timing will come into play.
FI will most likely get better MPG, and run cleaner Vs. a carb....but IF the tune is right on the carb...very little difference.

Cam and compression will dictate timing.