If you upgrade your fuel pump to something like a Walbro 255 in tank kit, will that change the way the car runs in terms of a/f ratio? For instance, you have a bone stock ITR, and install the Walbro pump, and dont change fuel pressure or injectors or anything at all, will the car run the same since you are on the same pressure and injectors? or will it be a lot more rich and run like crap without something like a VAFC to tune with?

 

Most likely the pump curve is different and it will flow more fuel at same pressure. You'll need an adjustable pressure regulator and some tunning to get it back to norm.

 

more fuel at the same preasure?

 

Diablo, are you sure? I was under the impression that the pump is CAPABLE of flowing more fuel at higher pressures, but if at the same pressure as stock, the same amount of fuel will be going into the motor even with the upgraded pump.

 

no, not positive.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2R &raquo;</TD></TR><TR><TD CLASS="quote">Diablo, are you sure? I was under the impression that the pump is CAPABLE of flowing more fuel at higher pressures, but if at the same pressure as stock, the same amount of fuel will be going into the motor even with the upgraded pump. </TD></TR></TABLE>

The fuel pressure regulator and return can only take so much fuel, so you may end up with more fuel pressure than you intended.

YMMV... but when my tuner was tuning my GReddy the first time on EManage, he was getting way too much fuel and blamed it on the stock fuel system with a 255 LPH pump. Switched to a 190 LPH and retuned with Hondata at the same time, so I can't say if it mattered or not.

 

having thought about this a bit more, as long as you don't change injectors you should be ok....as long as you don't overtax the fpr

 

overtax meaning the fuel pump pushing more fuel than the FPR can handle at a certain pressure?

anyone else chime in?

 

You will be fine...

 

Why would you upgrade? Unless you have a large need for an upgrade, I would stick with a stock one. I am still running the stock fuel pump on my setup without any problems....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">... as long as you don't overtax the fpr</TD></TR></TABLE>

... and the ability of the system as a whole to return the excess fuel to the tank.
This is going to be a problem with the newer systems that don't have an excess fuel return system from the FPR.

 

I have a Walbro 255hp lph fuel pump in my 91 CRX Si which is bone stock at this time and I accutally get better gas milage now. I repl because the oem one went out, and Im bout to do a LS swap with boost, so thats the reason. No problems so far, have put about 2k miles on so far.

 

Brad, bc I think my stock one is screwy...makes a weird sound when priming after I turn the key to "ON".

I ordered one so we will find out soon enough

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2R &raquo;</TD></TR><TR><TD CLASS="quote">Brad, bc I think my stock one is screwy...makes a weird sound when priming after I turn the key to "ON".

I ordered one so we will find out soon enough </TD></TR></TABLE>

Just wait until you install the aftermarket. The noise can get annoying.

 

for those interested, I installed the 255lph Walbro pump. and with no other changes, the car seems to run exactly the same (did not hook it up to a WB before or after so just judging by daily driving experience). Im curious to see if gas mileage changes, but I havent driven it enough yet to notice.

I did notice one difference and not sure if its related to the pump or not since Ive always sort of had this "problem"; my idle stays high a bit longer when coming to a stop. but that could also be because of the cooler weather lately which is noticable because of another "mod" I have.

 

Wow. Keep us updated on whether or not this makes a difference with your fuel mileage.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">Most likely the pump curve is different and it will flow more fuel at same pressure.</TD></TR></TABLE>

Volume of fuel flowing through the same size fuel lines cannot change without a pressure increase.

 

so what you are saying is that it should be flowing the same amount of fuel, unless I turn up the fuel pressure? thats how I imagined it worked but dont know for sure.

 

I'm in the same situation as you too. I bought my car with stock intake, header, and exhaust with AEM Fuel Rails and Walbro 255 Fuel Pump but I'm still getting 240 miles to a tank so that's not bad with part time Vtec!