burbling1

iTrader: (1)

What is a fuel pressure regulator? were does it fit? and what are the benefits?

Only reason I ask is that my wagon sometimes missfires and am starting to look towards the fueling after changing the MAF, plugs and lamba.

Its running a full decat, chipped z4 and tdo5 and am thinking that the injectors could be at there limits after reading that they are good for 279bhp at standard pressure or over 300 with 3bar fuel pressure.

Thanks.

Normski

The FPR fits on the end of the fuel rail, an adjustable one would replace your existing one, but it would be too big to fit in the standard position so it would need to be mounted where there is space. An adaptor fits in the standard position and connects to the FPR with fuel hose.

A FPR is there to maintain a constant fuel pressure at the fuel injector. A base pressure is set (3.0 Bar usually but earlier cars have around 2.7) and this is then varied relative to the air pressure inside the inlet manifold.
E.g. at idle there is a partial vacuum inside the inlet manifold - 0.6 Bar, this would pull the fuel in too much, so the FPR reduces the pressure by 0.6 Bar giving 2.4 Bar fuel pressure.
Also when on boost at say + 1.0 Bar, the FPR needs to increase the fuel pressure by 1.0 Bar (to 4.0 Bar) as the fuel would be held back some what otherwise.

With an adjustable FPR you can raise the base pressure, and so get more out of a set of injectors, but a re-map would be required as the fuel would be increased everywhere.

Have you checked the coil pack/s?
When does it missfire?

tweaks

iTrader: (7)

what plugs have you put in ? did you gap them correctly and also as above remove boots from coilpacks and checked fo cracks etc....???

burbling1

iTrader: (1)

I have checked the coilpacks for crack ect but no joy. I have 7s in I think did have 6s.
Seem to miss around 4000-5000 when under full load, also seems to do it more when its very cold outside.

mit

iTrader: (10)

I had the exact same problem, missing at 4-5k. I fitted 7's, and gapped them to .6mm. The high boost can actually blow the spark out, so the smaller gap prevents this. Runs with no problems now.

tweaks

iTrader: (7)

fitted 7's to mine and after about 2 weeks started to do the same.
tried loads of different things on it and after a week of headscratching
decided to try my old plugs again.

turned out the new 7's i'd put in,2 had cracked down the insultor round the base of the electrode !!!! sent them back under warrantey got some new ones in all has been well
ever since.

burbling1

iTrader: (1)

hmmm how interesting.
Sounds like am going to have to spend an hour under the bonnet this afternoon removing plugs and washer bottle and airfilter and.......
Flat 4 why o why