Another VAFC HACK Testimony - Honda Prelude Forum

Blaast · 09-06-2002, 07:35 AM

Just wanted to let you guys know what I did today:

I removed the synapse MAP bypass, ditched the 8:1 RRFPR and tried to use the VAFC HACK.

I have 550 cc/m injectors with in-tank bosch pump.

The Hack using the throttle position maps plugged on the MAP signal doesn't work with 550cc/m injectors. It runs too rich.

The Hack using the normally wired VAFC without throttle mapping works fine. Instead of setting the correction to -40% as with 440 cc/m injectors, the correction needs to be -50% with 550 cc/m injectors. This is borderline though, since it still runs rather rich (high 13:1 ratio, sometimes 14) and of course, no way to further lean out the mix.

Still, this is a significant improvement over the 8:1 RRFPR, which was getting over rich in high RPMS.

Who knows how to further lean out the mixture when the VAFC is already at -50% ????

WHat if I go back with the stock pump?

Quaalude · 09-06-2002, 09:11 AM

yeah, the stock pump should help since it doesn't flow as much as the bosch....also if you have an adjustable fpr, then lower the fuel pressure

schwett · 09-06-2002, 10:48 AM

yeah, i'd suggest you lower the fuel pressure 5-10psi. that should help significantly, especially if you have a high flow pump that's backing up the stock fpr.

you really can't keep pulling fuel by reducing the map signal; the ecu only has "table" for a certain range of vacuum, ya know? it gets less and less effective as you lower it more and more. sounds like you're fairly close though, so fuel pressure should do it.

99Prelude_LC · 09-06-2002, 11:31 AM

Quote:

Originally posted by Blaast
This is borderline though, since it still runs rather rich (high 13:1 ratio, sometimes 14) and of course, no way to further lean out the mix.

i dont' understand, isn't 14:1 lean on an a boosted car?

schwett · 09-06-2002, 02:43 PM

he's referring to closed loop, i hope, which is what the narrow throttle settings on the vafc are for. in closed loop it should average out to 14.7:1 over time.

Quote:

Originally posted by 99Prelude_LC

i dont' understand, isn't 14:1 lean on an a boosted car?

Blaast · 09-06-2002, 03:22 PM

Yeah, I don't understand too much either. While the APEXI auto -timer reads13-14 :1 ratio, the J&S A/F gauge remains in the green all the time.

I think I will try to get a used FPR to reduce pressure. Otherwise, I could sell my RC eng. 550 injectors and get some used DSM 440 for cheap.

Funny thing though: I did a reset on the ECU and the car now pulls much better. I think I'm gonna cut the ECU memory wire on the ecu, on order to have it reset every day.