Unless you have the high pressure version of the 255lph pump which I think almost no-one has....

I would never use a 4 bar FPR with the OE pump, it isn't built for it. Unless you want to run 0.8 bar boost then it would probably be ok

so johns,whats your suggestion for the above mods?
should i or shouldnt i use the 4.0 bar fpr?????

Hi,

I and my friend are using adjustable FPR together with Walbro 255HP pump. I run with 3.8 bar and my friend with 4 bar fuel pressure, neither of us have had any problems what so ever with that combination. Okay OE injectors are pretty much in limit above 340 bhp, A/F was, according to wide band lamda, around 13-13.5.
Also with boost of 1.6 bar I have never seen the fuel pressure under 5 bar, also in high rev's. The fuel flow is no issue with 255HP pump and high boost.

- Jari -

thanks jari,
SO many different opinions though.....
anyone else?

If you are just sticking a plug and play chip, then I would only fit an uprated regulator, IF you have an uprated fuel pump AND access to a wide band lambda to check the fuelling.
Even then ,it should only be fitted if you have documented fuelling problems.
Still this is very crude, and you will increase fuelling slightly across the whole rev range, at idle, part load etc etc , so is not ideal.

An uprated FPR can be used, of course with a custom ECU, mappable UCU, to wring a tiny bit more out of the injectors, but its hard to know how used OE injectors will respond, and again you will be increasing the fuelling at other parts of the Maps that say a piggyback ECU doesnt deal with ,say the Unichip for example, doesnt compensate the idle map.
When I spoke to Paul, he suggested, that at most you might get an extra 5% out of the injectors, really I think this is the most appropraite time to fit uprated regualtors.


The trouble is , a lot of peepes read these threads, and end up bunging on uprated regulators, in inappropraite situations ,just because 'everyone else has done it', and then never get things checked professionally ,and then wonder why their engine either breaks or loses power later on

Joe

thanks joe,thats very informing.....