red12secz28

I have a 98 vette with the return style fuel system. I been noticing when I'm logging with efilive that when I do a full gear pull; when I start at 2,500 rpm in 2nd gear and pull it to 6,500rpm full throttle, that the car pulls knock consistantly around 5-5,200 to 6,500. Also I notice a flat fuel curve while logging the o2's. They read about 890-920 mv until they hit 5,000 and start to drop 50-100 mv. But what gets me is that if say I hit full throttle in 2nd and pull from say 4,000 to 6,500 the car shows no signs of knock( which I think is induced because of the sudden fuel pressure drop) and the 02's stay flat at around 900 mv. My injector duty cycle is about 80% up top. Do you guys think if I change My fuel filter I might get away with not have to change a fuel pump.

muncie21

Sounds like you are losing fuel pressure. Put a gauge on it and find out for sure.

Oh yea, I'd highly recommend a Wideband if you are tuning. Reading the stock O2 signals only tells you if you are at stoich (14.7) or not, they can't tell you how far away you are....

red12secz28

I have a wideband. I went to the dyno and tuned wot fueling. 910mv is where the 02's on the car correspond to the wideband afr of 12.9. Since I don't have the wideband always hooked up I guestimate using the cars o2's with a certain amount of safety. Just recently I started to feel the car pull power.