Porsche Enthusiasts Club Forum

I have a very late 1991 944 S2 with a 1991 turbo engine swapped in. A previous owner has fitted a manual boost controller and Promax DME/KLR chips, but they didn't upgrade the FPR or the wastegate. Right now when I try to raise the boost, it runs fine until around 8psi, when I hit knock protection. I suspect that this may be caused by the OEM 2.5bar FPR (the ProMax chips I have fitted recommend a 3.0bar fpr). After looking for upgraded FPRs (on Promax, JMG, Lindsey Racing sites) it seems that almost all upgrades relate to the early 944 turbo engine which has clamped push-on fittings to the FPR. However, my engine has the later threaded fittings as fitted to an 944 S2, so the standard upgrades won't fit without altering the fuel lines.

So now to my question - is it possible to use a 3.8 bar fpr from an S2 with my setup? I really don't want to cut into my fuel lines just to fit an uprated FPR (I always like to keep the path back to stock condition viable). From my understaning this should cause a slightly higher electrical drain (due to the injectors having to work harder to close), but the duty cycle should be less, and AFRs should be unaffected.

Has anyone else done this?

Isn't there two types off 3.bar fpr

191690683232 eBay item number

That is the 2.5 bar version that I already have. I am asking if the 3.8 bar version from a 944S2 will work with my Promax chips.

If you can't find an equivalent 3.0bar one off another car then I suggest your best bet is to 'back date' your fuel rail to the earlier type. There's loads about as they're the same between NA and 951's.

The correct fuel pressure for the map is pretty critical though.

There is not a threaded 3 bar FPR. You have to modify your hose to suit the non-threaded type.

Also, you must use a 3 bar FPR with the Promax chips to ensure correct fuelling.

Stuart

I was hoping that someone else had already tried this, as I have done similar things on other cars and it can work. It really depends on how capable the DME is on managing closed loop. The 3.0 bar fpr is a 20% increase, and the DME seems to be able to manage the pulse duration so that it doesn't over-fuel in closed loop. The big question is whether it could handle a 50% increase, and the only way to find that out would be to test. On WOT it will depend on the chips - and the only way to check that would be with an AFR gauge and a dyno.

Feck it, I give up - I have ordered the 3.0 FPR, and I will have to butcher my pipes.

Could replace the fuel lines as they go in to the engine bay. There's kits on ebay. Iv got some from larts parts. Could make up yourself, just finding the right fitting for fuel rail end. Could reuse your current fitting maybe. Not something that's worth risking leaking. Found mine leaked after 1st install. So be careful.

I wouldn't use a 3.8bar FPR if I was you, you could risk bore washing the bores with that much fuel pressure...try these people. http://www.glencoeltd.co.uk/ I have used their adjustable FPR's for many years with great success, source a small fuel gauge too and either fit it to your fuel rail or the FPR itself so you can set your pressure very easily in seconds without the need and hassle of setting up a testing gauge. Just tell them what your requirements are and I'm sure that they will be able to sort out the correct unit to fit your car.

Pete