can i run about 8-9 psi w/my 12:1 FMU??? my fuel set up includes.....

vortech 12:1 FMU
B&M FPR
Walbro 255lph f/p
stock injectors

and i wana run 8-9 psi (most likely 8)

can i do this or will i have to buy a 10:1?? if soo how much is that?? thanx....

 

From what I understand if you have the Intake 255lph fuel pump, it will start to lean out once you get to about 90psi. of fuel pressure. With the 12:1 FMU at 5-6psi. you would be at around 90psi. of fuel pressure. So what I would do first if you plan on running 8-9psi. would be to get a Inline fuel pump like the Bosch, Aermotive, MSD, etc. something that flows alot of fuel so you don't lean out. But if you decide to get the 10:1 FMU you will probally be safe with 8psi. but put a wideband 02 sensor on their to make sure. That is the most effective way of checking your air/fuel ratios. Also, you might want to upgrade the injectors, not sure if it is nessesary but I would. Get some RC 310cc injectors if you only wanna run like 8-9psi. but you will need a VAFC or somekinda fuel controller so you can adjust the fuel percentage so you car will idle fine. Cause if not the car will bogg and idle like poo poo! Well I hope this helps.

 

well i do have a vafc....and im gettting the car tuned when the turbo is put on...but i wanna run 8psi...i kno i can keep the stock injectors....but about the fuel pump....why wouldnt i be able to use the walbro...dont alotta people use it?? i dont remember if its the intake or inline....i'll findout though

 

its a "high pressure intank 255lph walbro"

 

Anything over 80psi on an intank pump is asking for trouble. If you want to keep the stock injectors and go the high pressure route, you'll want a high pressure inline pump in there. Drop the FMU rate down to like 8:1 for 8psi. That's an additional 64psi of fuel under boost + your static 40is and you're already looking at over 100psi of fuel at the rail and behind those tiny 240cc injectors.. I'd say thats far enough! Next best thing, upgrade your injectors to some 310's, leave the 8:1 FMU and dial back a little on the AFC when/where it runs a little too rich.

 

Still put out less than good inline's

 

If you do not believe us, look at the Walbro supplied pressure graphs... no flow after 90psi..

 

so which one should i buy??? in order to run 8 psi....with the fpr..and stock injectors

 

Find an inline pump that can build 125psi... there are a couple on summitracing... or the airtex pump that comes with the DRAG kit.

Dustin

 

the bosch unit might be a choice

 

This one. Bosch inline.


If you really wanna lean out and eventually blow your motor stay with the walbro

 

http://www.autoperformanceengineerin.../fuelpump.html

 

so i need an inline fuel pump...so does that mean taht i have 2 fuel pumps now???

 

yes

 

so what pump do i get lol.......anyone....

 

dont listen to these guys, there are a few people here using
12:1, stock injectors, and walboro pump...
turbointeg95 to name one... look at his profile.!!

 

yeah but eventually im gonna boost higher....so i need the right pump.....and disk.....what pump do u guys recommend

 

the walbro gss-342 still flows enough for your needs at around 110psi; past that you're hosed. i'd play it safe, get slightly bigger injectors, the 342 or similar bosch unit, and a lower rising rate. i've had good experiences so far with the cartech 2025, which has an adjustable rising rate. might not be the right thing for you, but it's nice to be able to adjust rr by turning a dial.

 

are u serious?!?!!? u havent read a damn reply have u.!!![


[Modified by Giuseppe, 5:22 AM 2/11/2002]

 

No.

 

at 100psi that pump flows 113lph, or 113,000cc/h, or 470cc/min per injector. a 240cc injector at 90% duty cycle flows 330cc/min at 100psi. so the pump is well ahead of the injectors. at 110psi it's slightly behind (290cc/min for the pump vs 345cc/min for the injectors.) so you're right, it's not enough at 110psi but it's somewhere very close to it that the pump starts losing ground. call it 105psi.

i know this from experience, not that it's a setup i would recommend.

 

ok here we goo.. my fmu if i change the disk to an 8:1 means that for every lb of boost it is 8 psi of fuel pressure...if im right there its 64psi fuel pressre plus 38 psi stock so that is 102psi....and that is too much for my injectors (I WANNA KEEP THE STOCK ONES) and my stock fuel pump...so i now need a better fuel pump or a second one...so if i buy an intank i will still only have one and an inline i will have two.....if i get the inline it will be better now and in the long run....but what about an intank...and what fuel pump does everyone recomend? lol tia

 

I don't think an 8:1 disk with stock injectors is going to provide enough fuel.