bewst12psi

iTrader: (7)

I rented a dyno for the day today to tune my car. Its an S4 TII with the following mods. That could be related to the issue

Vmount IC
precision PT 6262sp billet wheel turbo
custom UIM with 80mm TB
1000cc primary / 1000cc secondary injectors
-8an fuel rails w/ -6an ss lines from the factory hard line.
Aeromotive FPR
Walbro 255hp pump. In tank.
Haltech Platinum Sport 1000
Stock Port S4 motor
Full exhaust, 44mm external gate.
Running 20psi

Fuel settings in the haltech are:
-sequential firing
-staging mode: Primary Hold
-staging load :2.0psi
-DisEnrichment 0.0ms

- start tuning the haltech. light throttle and cruising are taken care of.
-move onto load pulls.
-3k to 6k are tuned dead on to 11.8:1 afr across the board
-went for some higher rpm pulls
-6400rpm is leaning out to 12.2 and by 7700rpm, its at 13.8.... not safe or good.

No matter how much I richen the base fuel map, it stays at 13.6-13.8 in the higher revs.
i went from 14ms all they way to max at 32 just to see what happens... no difference.

-Do another pull and watch the fuel pressure. base pressure at idle is set to 43psi. At roughly 5800 rpm when its making the full 20psi of boost the fuel pressure is about 60psi. it then fades off to 43psi by 6700rpm with my Aeromotive FPR where it will stay.

Heres is my headfuck... are my fuel settings possibly off? or am I running out of fuel? Isn't one walbro 255hp sufficient for my setup?

I removed the fuel filter and ran it straight from the end of the hard line to the rail to make sure that the filter wasnt a restriction, but had the same end results.

Do I need to run larger fuel lines (I have stock hard lines from the 255 pump to the -6an line where the hard line ends.... or is my 255hp pump just not enough for the 4 1000cc injectors?

Any input is apreciated... It really pissed me off to waste $ for a whole day of dyno time and no final results.... it did still make 402 hp though

bumpstart

the fuel pressure falling off is telling you something

no changing of the map is going to account for a weak pump

firstly,, upgrade the wiring to the fuel pump,, using a relay and fused feed from the battery
( and perhaps double up the earth from the inspection cover )

secondly change out fuel filters

retry

if still at issue,, then the pump just is not up to it,, tired or possibly fake
good thing about a walbro is its slim enough to get two side by side into the tank

Elcoete

Just wondering did you ever figure out the issue. Working on a 88 rx7 just gathering info as I build it.

peejay

402hp (wheel?) with a 255 is doing really well.

Look at it this way... 255 liters per hour is 4.25 liters per minute (and you have 4 liters per minute of injector!), but that is at 42psi. Flow goes down as pressure goes up. At 60psi it will be flowing a lot less than 4.25 liters per minute.

Also, fuel pressure should be 63psi at 20psi boost if your base pressure is 43psi.

Aeromotive makes a 340lph drop-in replacement for the 255 but I'd just as soon run double 255s instead. I don't like the idea of running "just enough" fuel pump, because it is "just enough" when it is new, and age will make it "barely enough" and then "not enough" and then you hurt things if you aren't paying attention.

bewst12psi

iTrader: (7)

It was the fuel pump... I put a supra pump in it, rebuilt the engine with turblown studs and made 500whp. The fuel pump was failing at higher pressure

Sammy Built

iTrader: (18)

Thats great to hear

misterstyx69

iTrader: (142)

His wallet would beg to differ on that statement!..had to rebuild..ahhhh Gawd nooo!