EFI Puzzler

[parsonsj]

Mike Norris and I were messing around with II Much yesterday, and one of the things I wanted to do was to increase the fuel pressure in the fuel rails. I've been running at 42 psi (or 38 depending on which gauge you believe).

I wanted to run at 58-60 and see if there was any more power or if the idle would be smoother due to increased fuel atomization.

I bumped the pressure to 60 (Aeromotive rails, regulator, A1000 pump) with no problem. However, the motor went lean. Mike started tossing in fuel and it made no difference. Thinking the o2 sensor might be the culprit, we swapped it over to Mike's dyno sensor, and saw the same results.

Next, we reset the pressure to 42, and reloaded the original fuel map that Mike had saved (he's a smart one). Everything went back to normal. Then we increased the fuel pressure with the engine running. The engine went progressively leaner as we did that.

Not knowing what else to do, we put everything back and I drove the car home.

The only thing we could think of is that the injectors (Holley 42 lb) aren't rated at pressure higher than 42 (45?) and the high pressure prevents them from allowing more fuel by. Does that make any sense at all? Is there a different brand injector that we should try? Or is it even worth trying to get to 60 psi?

Thoughts?

jp