Seems everyone with FI wants to run these Walbro 255 pumps. Im currently running a stock Integra pump in my Civic and have seen no problems from lack of fuel pressure or running lean on the wideband. This is with stock regulator and rail as well.. so my question is when do you know you need a larger volume pump? When fuel pressure drops at higher rpms would be my guess, but it seems like a blanket thing for people to change the fuel pump whenever they go boost..

 

You are obvously not making much power. But yes, you know you are out of pump when your duty cycle is higher than normal for the size/power level, and the fuel pressure does not hold

 

I guess that all depends on what you consider "much" power. It holds it own but I am only running 9psi right now. Id say its somewhere in the 200-210whp range give or take. Im not trying to make 900whp or anything. This is my daily driver. For now I am only running 550cc injectors and sitting around 60% duty cycle according to Ectune. I am planning on getting some larger injectors and heading to the dyno with hopes or 350 or so whp.

 

From what I gather a stock dohc vtec pump is around 135lph. So guessing that's good up to about 300 max. Personally I wouldn't do 250+ on a stock pump

 

the bigger pump becomes necessary when your injectors are so big that there isnt enough flow into the rail

 

Must people run the Walbro pump because they are pushing more than 300whp. Everything fuel related besides the pump and injectors is good for maybe 600whp. I read one of your later posts, you are probably on the boarder regarding needing a fuel pump with your power level. I say if your making the power and everything is working fine then don't sweat getting a fuel pump.

 

Well, working fine for now... but I want to get the boost up a little bit and shoot for a larger goal... thus raising the question of should I consider the pump.

 

Safe insurance so why not.

 

Funny you raise this question, I asked back in 2008, had the same replies too.
I was running a built B16 and ran 350hp on a stock pump for 4 years and no problems,
I them changed to an in tank 255 and the pickup requires no less than 10ltr in the tank,
Back to back at the same power level on the same 550cc injectors duty didn’t noticeably change.
Yes good insurance for the cost but I’m still undecided.

 

Depending on the size of the pump determines it's "theoretical" max power capacity. IIRC to get that max power your pump will handle you take the pump flow in lph and divide it by your BSFC.

i.e.
160lph Pump
BSFC of .55

160 / .55 = ~290hp

Your BSFC is the factor that determines the pumps "theoretical" maximum capacity.

 

Remember that your pumps are 10+years old and can fail every minute.

a new pump, feks the walbro is a cheap insurance.