So apparantly my fuel pump has been going out for some time. I put a gauge on it a couple days ago and drops from ~35psi to ~30psi at WOT. I believe normal fuel pressure at WOT is somewhere in the neighborhood if 47psi. I am also of the understanding that injector pulsewidth is calculated from tables in the PCM and there is no correction, unless the long-term fuel trim affects the WOT tables. Would anyone care to explain to me how this works? I have a Racetronix pump going in on Saturday, but I'm curious how much power I'm missing out on right now.

 

Hell with the HP loss, I'd be worried about blowing up the motor. Running lean is the worst thing you can do to a motor.

 

Yeah, I was worried about that too. Fortunately it holds pressure at light to medium throttle openings and RPM, so I'll be fine till the end of the week. I have no idea how long this has been going on, but I would suspect a while. My plugs have always looked "normal", and I've never heard any pinging or detonation so I assumed everything was fine. I guess I was wrong. Thank God for forged pistons and cold plugs. Soooooo, now that everyhing will be fixed in short order, anyone care to quickly explain how the PCM adds fuel under WOT?

 

It keeps the injectors on longer with a longer duration pulse width.

Running lean isn't the worst the thing you can do to an engine. Try running without water or oil.

 

Since the fuel pressure is holding "normal" levels at part load (closed loop), the long term fuel corrections should not be affected by the fact that its only leaning out at WOT. When you go WOT, it will be using the long term corrections that you developed with full fuel pressure, so its going to lean out.

"Standard" pressure for the flow rating on the stock RP injectors is 43.5psi (factory specs accept 41-47psi range). With only 30psi at WOT, your are only flowing about 83% of the fuel that the PCM thinks is flowing, and there is no feedback to tell the PCM that its running lean (PE mode). If your "tune" was for something around 12.8:1 at WOT, its probalby running about 15.4:1 with the shortfall on the fuel.

 

Thanks Fred, that's what I was thinking too! And Speedy, I'll agree that water and oil are very essential things to have! Ask me how I know this.