I had a post in the COS forum, but not sure if it goes there or here. If I'm wrong, please advise. I just swapped a marine intake and Whipple supercharger onto my 1998 GMC with 5.7 Vortec. The intake allowed me to run proper injectors, Bosch 0280155811 at 3.5 bar. Stock they flow 36# at 43.5psi, so using this calculator
http://users.erols.com/srweiss/calcpchg.htm
and some googling I arrive at 38.888 lb/hr and an IFR of 4.8988. I plugged that in (or something close to it) and the truck fired right up. Trims are off which I wasn't expecting at low load plus I have this NASTY off idle stumble (all other transients are fine) that's worst when the engine is cold. I don't want to go changing a bunch of crap in the wrong order. The truck seems to run better if I fudge the IFR down I believe in the 3.55 range but I assume that's just covering up the real problem. So should I have faith in my IFR math and just go do a calc.vet or is there more than meets the eye when it comes to nailing down a new IFR? Or is there some super simple idle setting I'm totally missing here? My only thought is the addition of some real estate between the engine and the MAF with the supercharger being in the mix now. Physically its location has remained the same as stock.
411 Whipple V1.tun
411 Whipple V2 IFR Change.tun