Walbro 255 Fuel Pressure

[SleepingTsi94]

I have a walbro 255 that iv been waiting to install. I have my afpr now and I did a search and was finding that people say keep it at stock with the vacume line off. Is this right? If so then what is the reason to not just use the stock one?

 

[SpeedAddict62]

The orifice in the stock fuel pressure regulator is too small to flow enough fuel to regulate the fuel pressure with a pump that big. This means the pressure tends to fluctuate, and makes tuning difficult. As an axample, I have a 255 installed without an afpr, and my fuel pressure at idle is close to 40 psi, with the vacuum line ON. Obviously, this isn't a good thing, but I haven't gotten an afpr yet and the car runs fine without it. Of course, I haven't tuned it either.

 

[SleepingTsi94]

So I think the stock fuel pressure is 38/9 should I set a little lower than with vaccum line off?

 

[Quasimondo]

Set it to 37 psi without the vacum line attached.