Can the VE tables compensate for returnless fuel reg?

[Michael Stora]

The returnless 58 PSI fuel system used on '99-'03 Corvettes is very popular with hot roddres and good to about 600 HP. It is very stable, just not manifold-referenced. Since we have a VE table based on MAP anyway, why can't we fudge the low pressure values down slighlty to fully compensate for the fuel pressure differential across the injectors.

I have such a setup and I was thinking I'd have to swap it out for a conventional return system to use MS.

Quick back of the envelope calculations would indicate that for 58 psi, you'd have to lean out your VE by 9% at 25 kPa. There is no danger of a lean detonation while tuning, because if undercompensated, you'd only get richer with load.

Mike

[PSIG]

Many MSers have used non-referenced regulators with fixed rail pressures. While MS 'expects' there to be a fixed differential between the MAP and rail, you can generally tune around it with full control. Go for it.

David

[insanezane]

if gm can do it you can too just do like you were saying and if you don't take enough it will be rich and you can take out a little more at a time till you get it right a good wide band would make it easy but you could probably get it to drive ok by ear Zane

[jakobsladderz]

The only issue with using a returnless configuration is related to the injector pulse resolution. For a naturally aspirated engine with a manifold pressure range of say 0.2-1 atmosphere, there shouldn't be too much trouble so long as the injectors are not overrated for the engine (otherwise it may be hard to get a stable idle mixture). For a pressure fed engine there may be issues.

With manifold reference the amount of fuel injected per cycle (turndown ratio) varies over about a 5:1 - 6:1 ratio (more for a blown engine). With a fixed fuel pressure (relative to atmospheric) the turndown ratio may be more like 15:1 - 25:1 for an NA engine. I would suggest that you'll need MS1/Extra or MS2, the original MS1 might not have enough injector resolution (I think it's 0.1ms or something, probably too big a step).

Cheers

[insanezane]

yeah this is true or aeromotive and some other companies make a voltage controller for the pump similar to what oem uses but i'm guessing that would do away the cheap cause i already got it to use method of the setup. Zane