My Walbro 255lph and my Forge MBC should be here any day now, and id like to install them just to save time later. Its going to be a few weeks before I can get the car tuned though, and I am not sure if I can just install a new pump like that??? Im going to set the MBC to 20psi untill the tune obviously, but I would like to have everything in ready to go before my tune. Im not 100% sure exactly how a bigger fuel pump works? Does it ALWAYS pump more fuel, or will the stock ECU just take what it needs? Thanks guys.

 

shouldnt be a problem. Its controlled by the ecu. But when you NEED the fuel a bigger pump is necessary.

 

it all depend nobody know how good you are with your hands,but it should not be that hard it's wright underneath the back seat.

 

heres a post i made about the evo 9 fuel pump vs the walbro:

https://www.evolutionm.net/forums/sh...d.php?t=258235

hopefully that helps. cliffs notes:

stock 9 pump is sufficient for minor bolt-ons such as exhaust, MBC, Intake and a tune. adding the walbro will not necessitate a tune.

 

Wow you guys answer QUICK!! Thanks! I will go ahead and install it once it gets here! Bluebyu36, thank you for your help, but I was not asking about the install itself. I just needed to know if the stock ECU would be able to use the new pump without a tune. Thanks again!

 

I wouldn't reccomend the pump till you do a lot more mods, I lost 20whp when I installed my walbro pump with only an exhaust & MBC, so I had to take it back out.

Then I later re-installed the pump after I did HKS cams, 3" downpipe and open air-filter was running 21psi tapering to 19psi.

 

It's a little rule (actually a big one): if you add/reduce the amount of fuel or air, get a tune.

 

If the fuel pressure remains the same, than you dont need a tune, and since the ammound of fuel coming through remains the same, your fine. Could use a tune though, as it will bring out the best and allow you to run higher pump fuel boost.

 

Dyno Flash Always Recommend Walbro 255 Fuel Pump On Every Single Evo Out There Before U Tune~

 

I would not suggest installing the 255 without a tune. Someone correct me if I'm wrong, but where in the ECU does it automatically correct for the increase in flow? It takes about 30 minutes to install, just wait for the tune, then do it. Not worth the trouble.

 

Do you NEED to tune the car, no not at all. Keep in mind here guys that you still have certain mechanical constraints on the system. The lines are the same, the FPR is the same, and the rail are the same so the volume and pressure are still basically the same. What we are doing is trying compensate for a small pump not being able to maintain a constant volume and pressure at higher loads. That means that when you are cruzing around at 35mph, you will still see the same driveability but when you are feeling saucy and crank the boost, instead of it breaking up due to a lack of fuel, it keeps pulling.

 

Exactly, the fuel pressure will be the same, so the injectors will be spraying the same ammount of fuel (in a perfect world) obviously the pressure will get a little higher, which will throw off your AFR's but they will only make it a little more rich and, well, that never hurts you, just lose a tiny bit of power. I installed my walbro, and havent felt a difference in power at all, in fact, it actually feels a bit stronger up top which is weird but whatever.

 

I see a tune in your mods list though? How long did you drive the car with the Walbro installed before you got it tuned? did it run fine untill then?

 

I have a wideband in my car

Just so you know.. My AFR's were 12.2 maxed out on stock pump. INstalled the 255 and went off the chart rich black smoke rolling from the exhaust and car felt like it was chained down..

about 3 pulls later after remaping and fuel was almost dialed in.. went from 8.7's to 10.0's @ WOT. big change.

It will increase fuel pressure 5-7 psi from what i understand.

 

D@MN! I guess ill just install it say the day of/before my tune then. I hear the install inst that bad anyways. Thanks!