quote:
Originally posted by Adam Wade:
*laughs*
As to larger injectors, if you build an engine to make more than about 10% more power than stock, you'll likely have to do something to increase fuel flow. Going to bigger injectors will mean your idle quality will decrease, and your roll-on from cruise will probably deteriorate a bit as well. Unless, of course, you switch to peak-and-hold injectors (low impedance_, but those need a different injector driver circuit to function as P&H injectors, and you'd need a different ECU or some kind of a "black box" between ECU and injectors. If you raise fuel pressure you can get more fuel delivery, but you may end up running rich at idle and part-throttle cruise because your minimum fueling volume goes up proportionally with your increase in fuel pressure. Adding a second set of "staged" injectors is a third possibility, but it even more complex than the other ideas, and usually more costly as well.
If you're building a motor that is substantially more powerful than stock, don't forget that you may well need a higher capacity fuel pump once you get the injector/fuel metering issues sorted out. Most fuel pumps can only deliver 15% more volume than max stock fueling, give or take (mostof that is to account for a loss in pump efficiency over the life of the pump). If the pump cannot supply sufficient fuel volume at max power, fuel rail pressure will drop after a little while at max power, leaning the engine out until there's not enough fuel vapor to reliably ignite and the engine quits.