I ask because I think my fuel pump is going out and was wandering if upgrading it would require the car to be re-tuned. So, basically, does the FPR set a certain pressure regardless of the pressure on its inlet side?

 

yes. no need to re-tune the vehicle as long as fuel pressure is same as before.

 

Forgive me, but I know that I will not have to re-tune if fuel pressure is the same. The question is whether or not upgrading the fuel pump will change the fuel pressure, all else equal.

 

Adam, if you put in the Walbro, your fuel pressure will jump to a steady 54 psi at idle with the stock fuel pressure regulator. Why upgrade the fuel pump? Do you have mods that need it?

 

In theory changing the pump shouldn't change the pressure. The pumps can all produce a lot more pressure than you need and that is why we have a regulator to bleed back the excess. You install a bigger pump not for pressure but for flow. If your fuel requirements are high a low volume pump may not be able to provide the flow required to maintain the required pressure under heavy load.

Of course in the real world there are other factors such as the size of the return valve opening that my cause a restriction and hence increase pressure. We found this with the stock FPR and upgraded to the AEM.

 

Aus, however in some applications, you want the higher fuel pressure. For instance, we found that an FI F20C produces more power when running with a base fuel pressure of 50-60 psi with full vacuum. This is when you are only employing an FMU for fuel enrichment.

So in this scenario, the smallest bypass orifice diameter actually works pretty well.

 

I already have the AEM FPR installed. It's just that I believe my pump needs to be replaced and wanted to know if upgrading it would require re-tuning.

 

Simple answer, if stock worked fine- an upgrade to a walboro 255 would have a minimal affect. Also it would lead to room for future improvements. Your biggest dilemma is knowing if the fuel pump is the actual problem

 

You're right, I'm not absolutely sure that the pump is the problem. But it has been making some really weird noises, and I can't think of anything else that is back there. I even heard it making really loud noises with ignition off after the car had been parked for hours. And the other day while I was driving I hit the gas and the car stuttered, made weird noise from the back and went lean all at once.