Adjustable fuel pressure regulator

[Greybrick]

Although these are generally considered to be a performance control I was wondering if any have looked at these in terms of FE on ecu controled fuel injected vehicles. In my case the fuel pressure regulator is preset, part of the fuel pump and inside the fuel tank so there may be no option. Thanks.

[Rower4VT]

It's doable. You'd just have to get at the pump to remove the regulator, then install an adjustable regulator somewhere else on the fuel line between the tank and the engine that is more accessable. In terms of FE, I don't know that it would help. I'm going to assume you have a EFI vehicle. If you were to lower the fuel pressure, the ECU would try to keep the same a/f ratio and would increase the duty cycle of the injectors to maintain fuel flow at the lower pressure. If you lower the fuel pressure too much, you'll eventually hit the limit of fuel trim management for the ECU, you'll be running lean, and you're "check engine" light will probably come on. In some cases you might be able to get slightly higher FE with it running slightly lean, but I don't believe you'd want it running lean all the time as a low fuel pressure would cause.

[kamesama980]

I've been in on a couple performance engine builds and know some people that have tried this, as far as fuel delivered it only changes a small amount and the EFI will definitely adapt to it via the O2 sensor. it's much easier and cheaper to just piggyback the O2 sensor to say the engine's running rich and runs leaner on it's own.

the other problem is you can only adjust it slightly lower before the injectors stop working right. then you get clumps of fuel instead of atomized fuel and your economy goes down the tubes.

[Greybrick]

Originally Posted by kamesama980

I've been in on a couple performance engine builds and know some people that have tried this, as far as fuel delivered it only changes a small amount and the EFI will definitely adapt to it via the O2 sensor. it's much easier and cheaper to just piggyback the O2 sensor to say the engine's running rich and runs leaner on it's own.

the other problem is you can only adjust it slightly lower before the injectors stop working right. then you get clumps of fuel instead of atomized fuel and your economy goes down the tubes.

Thanks, I hadn't thought much about modifying signals to the ecu from the various sensors, but will give it a look.

Cheers.