Knock all over the board

[Jonasterg]

I installed my billet adjustable fuel pressure regulator earlier today, then took the car out for a test drive. At WOT I was getting near 10* KR through 1st and 2nd. I raised the fuel pressure and got the same thing through 2 more test runs. (Fuel pressure was set from 40 to 50psi at idle. My fuel pressure gauge reads about 5psi high.) At idle, the O2 millivolts stayed between 400 and 500, I thought they should fluctuate a lot more. TPS and IAC are set correctly, I was running 17 psi for the 1st and 3rd runs, 15 psi for the second run. (Second run the knock was closer to 6*.) Is it possible that my O2 sensor went bad? Thanks in advance for any help.

 

[azgn]

your 02 doesn't do anything at WOT......sounds to me like you have too much boost for the fuel you are using....set the fuel pressure where the chip maker specifies, turn the boost down and start from there

 

[tim87tr]

Also, if you have the stock fuel pump, it may not provide enough fuel at WOT to keep up with the boost. My stock pump would only provide 50 lb at WOT. Verify this with your fuel gauge under the wiper at WOT, probably getting lean. Your scan tool would verify this with lower that 750 O2s at WOT.

 

[Jonasterg]

I'm running the Walboro 307 fuel pump, hotwired, and green stripes. I forgot to look at the O2s at WOT, I'll check that next time out. I'm not sure what fuel pressure the chip is supposed to be running, it's a Casper's Ultra (I think) with the 7 position thumbwheel. (Setting 2 is when I only got 6*, setting 3 hit 10*.) The fuel pressure gauge I have now is rail-mounted, so I can't look at it while I'm driving. I'm gonna get a new gauge within a week, the one I have now is reading wrong.

 

[tim87tr]

Good, you have a 307. If your fp gauge is not reading correctly, you could still have low fp and not know it. You can get a fp guage with the steel braided line to run up under the wiper for a fp check at WOT, and it will be out of site under the hood the rest of the time. I still think it is lean on the top end, unless that setting 2 on the chip is too aggressive for your octane, like azgn said. Be sure you know what the settings are or you might have more trouble when you go to higher boost levels. You won't want 6* kr then.

 

[Jonasterg]

I was running the TTA 237 fpr before the adjustable one, the car wasn't knocking at WOT in setting 2 or 3 (as far as I know.) I just got back from the beach today, so my car has been sitting for 2 days, the fuel pressure gauge read 15psi? I unhooked the pump harness and started the car, fuel pressure on the gauge went down to zero, then while the car was off, it slowly climbed back to 10psi. So obviously the gauge is bad. Where would you recommend I get a new gauge from? I've heard most of the ones mounted at the end of the fuel rail go bad. Also, the regulator is supposed to go from 30psi to 100psi(?), I just tested it and the gauge read 30psi at the lowest setting, and a little over 60psi at the highest setting.

 

[S2V6RACER]

You can get a high pressure isolator and mount a guage in your car.

I did that, as a matter of fact the autometer guage looks pretty good under the VDO's.

This is on the street car though.


I don't feel the need to monitor fuel pressure with a Weldon pump and a FAST system on the race car.