Ok I put the .59 bypass jet on my car to lower the pressure. I'm still siting around 80- psi on a 70 shot. What size of jet do you think I need to get it around 60psi? I have the walbro 255 and a SARD.

 

Luis, first of all, you need around 72 psi for 70 shot per http://www.seas.ucla.edu/~cheston/nosxplained.html which I think the source info is from Holley. Around 60 psi is what you would need for 50 shot.

As for jet sizes, unfortunatley it differs from size to size but you're not going to see any change unless you vary the jet sizes by .10. If you're getting 80 psi which a .59 (I'm getting 80 psi on a .55), I'd get a .70 jet and go from there.

 

i need to buy a new fuel pressure gauge b4 i can see what psi im at with my 75 shot

 

I read in a thread that ppl were running 60 psi without increasing the egt too much. so if we know that we are running really rich while spraying you have room to tune down the mixture and pull more power out of the squirt.

 

Exactly, but also the school of thought is to stay in between 12 and 13:1 for A/F, so your window of change isnt that great. I'm still looking for another source on what fuel pressure you should have for different "shot" sizes.

 

its all based on your a-f ratio.

According to some people 13-1 is still pretty rich. Ive read that 11-1 is ideal for the most punch with out detonation.
I guess it depends on how much you want the extra power.

 

Well all cars are going to be different, for example everyone says you need 70psi for a 60-shot, or 60psi for a 50-shot, but that is not always the case. Some cars run richer than others, some leaner, mine for example only required 55psi for a 60-shot and that was tuned to 12.5:1 air/fuel on the dyno. Just read your plugs that the the best way to tell other than getting on a dyno with a wideband o2 sensor.

 

It seems strange to me that the A/F varies so much across our cars. At WOT the ECU is in open loop mode, so it seems like the fuel pressures should be relatively the same
-hype