91octane with 1200cc and 2.4lt, fuel pressure is dropping from 60psi top 40psi @ 18psi of boost with a FP Black around 6k rpm, is this normal? and if no what could be the problem btw new pump, filter and injectors with upgraded fuel lines and rail.

 

https://www.evolutionm.net/forums/ve...0lph-tank.html

the pressure will always taper as the demand rises... thats normal.. i personally don't think you need a second pump at that level... but i'm no expert...

i've seen guys at 400hp run double pumpers... and 500 running triple pumpers...

best of luck... i'm sub'n cause i'm about to switch to 2.3 and black myself.... much more psi though

 

Granted, I am an idiot, but at just 18 PSI you should be fine with a single Walbro on 91.

Why did you even bother to increase the ID of the fuelrail and the fuel feed and return lines? You didn't need to.

40 PSI fuel pressure should be safe. Even 38 PSI is OK. But if you are worried then hotwire your single Wally with 8 gauge cable, or run a Kenne-Bell "Boost a Pump".

 

Your BASE fuel pressure at 40psi is safe. 40psi with 18psi of boost is no good. You should NEVER see a fuel pressure drop under load. If you are seeing one it shouldnt be that much. 1-2 psi and I would upgrade my setup. Also at 18psi the walbro is fine. You prob installed it wrong with the oring pinched so it cant hold pressure. Is the car hard to start if it sits overnight? That would indicate it losing fuel pressure while sitting due to an improper install.

 

at just 18 PSI you should be fine with a single Walbro on 91. but get a full blown twin fuel pump in tank would be okay on your setup i run this twin fuel pump on my car and it's very nice ,,,,