Ok so we all know how important our fuel pumps are and what can obviously happen if it fails.
I'm currently using a Walbro 255 and it's getting on for 5 years old. For what a new pump costs and the potential damage I could save I'm going to be fitting a brand new pump.
Don't really want to go with a Walbro again as I've read some horror stories recently so will more than likely go to someone like RCM.

Question is,
- would I require a map tweak after fitting a new pump ?
Currently got a 255lt one but quite tempted to upgrade to a slightly larger one for safety sake.

Any ideas ?

Thanks,
Matt.

 

as long as your fuel reg will deal with the extra flow with out increasing fuel pressure no mapping will need doing. I had the same thing a while back.

 

Yep I have an adjustable fuel reg.

So if I fit a larger pump but leave the FPR well alone all will be well ?

 

Hi Matty you should be OK with 255LPH at your bhp,how much boost/bhp you are running?


Jura

 

Should be as long as the pump flow rate is not massively different and your FPR is a good one. Do you have a guage on your FPR?

 

Currently making somewhere between 400 and 425 at 1.6 bar of boost.

 

Yep have a gauge on the FPR, runs at just over 3 bar at the min.

 

There you go then, If when you fit your new pump the static fuel pressure on the gauge is the same then it will be fine.

 

What Paul@Zen performance recommend?

I would say,your current pump will be OK at your current bhp,my friend running 460bhp at 1.7bar still with 255LPH fuel pump happily 2 years without the problems

Jura

 

Well just had a look at RCM's pumps...£150 !!

Any other pumps out there worth a look ??

 

Running HRC 340lph fuel pump at 490bhp


Jura

 

Guessing a HRC 255 will be good enough for my spec, you got a link ?

 

I'm not so sure about swapping fuel pumps ***** nilly without a remap tbh... As long as it's the same spec pump, it'll probably be fine, but otherwise my reasoning is as follows:

On full boost (at full chat), when you *would* get say 5 bar fuel pressure (e.g. 3.5 bar static, and 1.5 bar boost), something like a walbro 255 may not be able to keep up, so you get a gradual pressure fall off as the fuel requirement increases (higher RPM where you develop more power), so that at full chat at high revs, you may only get a fuel pressure of say 4.5 bar instead of the 5 bar you'd get if your pump could keep up.

The above condition would have been taken care of in the map, as the degradation would be gradual and probably quite consistent.

However, fit a larger capacity pump, and all of a sudden you end up with 5 bar throughout the rev range - this will mean that you end up squirting more fuel for a given injector duration, so the map will be out (on the rich side, which obviously isn't as bad as lean, but may still cause performance loss etc).

 

When I swapped out my standard pump for the Walbro 255 the ECU adjusted for the fuel difference pulling out fuel to make it run right. Was only running for a week before the remap but seemed fine.

If you have a FPR then it should be ok as said above, you can check the pressure is the same and the ECU should compensate for the slight changes.

 

Managed to speak to my mapper today and got an answer on this.
As long as I fit another 255 then I won't require a map tweak, my fuel pressure is set by my FPR so all will be good.

 

I agree with the above but any pump that can not flow enugh to maintain 3.5 bar static fuel pressure on a given boost level under load at the top end is under-rated and should not be in the build or mapped around. The is no harm in over specing a fuel system to leave head room and you would not have to run it ***** out.