sky-chicken

Does anyone know the best place for the fuel pressure sensor ?
I replace my boost gauge wit the Defi fuel pressure gauge (looks to strange the current boost gauge displays "0" boost)

Is there a good place on the fuel rail ?

RT

are you using a stock fuel pressure regulator?

sky-chicken

I'm going with the AEM FMU

RT

how does the tank return line connect to the FMU? -6 AN?

xviper

I'd put it "upstream" of the FMU. This will give you the best indication of what the fuel rail is getting. After the FMU is the fuel return line back to the tank.

RT

sorry, that's what I meant, I was wondering how the fuel rail (where the stock FPR sit) connects to the remote FMU (upstream of the FMU).

xviper

My only experience is with the Vortech FMU, but I am assuming that the principle is the same with the AEM. I apologize if I'm mistaken.
The stock fuel pressure regulator holds back fuel to maintain the desired pressure to the fuel rail. Any excess pressure is shunted out the fuel return line and taken back to the fuel tank. When an FMU is used, this return fuel line is fed into the FMU before the fuel is shunted back to the fuel tank. The stock regulator is like a dam that holds back and keep pressure up to a prescribed level. An FMU is like a much bigger dam that holds back even more pressure, making the stock regulator redundant. It's just simpler to leave it there than it is to manufacture a new fitting to take its place. Therefore, any fuel pressure gauge can take a reading anywhere before the FMU. It can even be before the stock regulator if that's convenient to tap into.

In case this isn't what you want, the FMU connects to the stock regulator by way of a rubber fuel line. The FMU should have a fitting in it already which you push the fuel line onto and clamp with a hose clamp.

sky-chicken

Xviper,

are you getting real readings after the OEM FMU ? I thought that up to 45 PSI the OEM fuel regulator does not let go any fuel but if it is greater that 45 it will release excessive fuel. Doe this mean that you read only above 45 PSI if you install it after the OEM regulator ?

xviper

I don't have a FP guage. I was merely explaining how the FMU ties into the stock system.
If I understand it correctly, yes, if you put a bigger dam or plug (which the FMU is) after the stock reg, the pressure will be higher and whatever the FMU is set for. Like I said, with an FMU, the stock regulator becomes redundant because the FMU keeps pressures above what the stock reg is set for.