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Aftermarket Fuel Pump Query, New Press Vs Old

skiwhine

By skiwhine,
in Engines & Forced Induction

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skiwhine Collaborator

skiwhine

Posted
Posted

now im thinking of putting in a new fuel pump, was gona go a ebay walbro job, now fitting a new pump i cant see it flowing exactly the same as the old (i would asume a little higher) now wid more pressure the injectors will squirt more petrol in cylinder, running rich? or will the standard pressure reg fix this for me? or will i need an after market reg to adjust?

-_-StRyDeR-_- Experienced

-_-StRyDeR-_-

Posted
Posted

so why is it that i installed a bosch 040 in my car and its now running VERRRY rich. i didnt touch anything with the fuel regs... i was told that installing the pump alone would not disturb the fuel pressure at all but in my case it has made it rich as...

im goign to put a aftermarket reg on it and get it tuned soon though.

BHDave Grand Master

BHDave

Posted
Posted

It is most likely due to your old pump being fairly tired and not being able to keep the pressure up to the rail at WOT.

My afr's dropped by 2 at the top end when i installed an aftermarket pump. idle and cruise mixtures were unaffected.

The thing is, even if your fuel pump can flow enough fuel that the reg becomes a restriction and so the pressure increases, at idle and cruise the ecu is still chasing a target mixture based on the o2 sensor input.

My stock reg and lines have no trouble maintaining stock base pressure with an 044.

RBwhatever Veteran

RBwhatever

Posted
Posted (edited)

Yeah I found my AFR's richened up after I swapped the stock one out for a walbro(oh no not walbro :)).

But as BHDave said, idle and cruise afr's weren't affected.

Edit: Woops spelt BHDave's username wrong...sorry Dave :\

Edited by KeyMaker
R31Nismoid Grand Master

R31Nismoid

Posted
Posted
so why is it that i installed a bosch 040 in my car and its now running VERRRY rich. i didnt touch anything with the fuel regs... i was told that installing the pump alone would not disturb the fuel pressure at all but in my case it has made it rich as...

im goign to put a aftermarket reg on it and get it tuned soon though.

Your previous pump was near dead, hence it was running lean.

So now you have a fuel pump that can match the flow required, the car is now running as it should be (rich as).

Putting an aftermarket reg will not make a difference to your problem.

I used a stock reg running 370rwkw as an example, many more i know have made over 400rwkw

You simply need to have the car tuned now you have correctly working parts, as opposed to before where you were running a car with parts that could have killed your motor

The Mafia Grand Master

The Mafia

Posted
Posted

well, I have been there and done that - and I experienced it first hand because I do the tuning and mech work.

I had a Walboro that couldn't keep up at 300rwkw, and must have dropped pressure a little bit. When I had the car on the dyno, the AFR's leaned to 12.7:1 but that didn't matter as I have water methanol injection.

Anyway, my car was tuned for a pump that was delivering below 42psi at high load.

I put a Nismo 275lph pump in, and it now had enough grunt to delivery a full 42psi to the fuel pressure regulator.

AFR's dropped to 10.7:1. So the pump ust have been dropping a fair whack below 42psi.

Just remember, the fuel pressure regulator ONLY keeps the pressure at 42psi if the pump is able to deliver more. If the pump can't deliver more, the FPR can't do its job. All it does is returns any fuel over 42psi back to the tank.

If all that makes sense. You don't need a new regulator. You need a pump that can keep up to your demands.

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