Adjustable FPR- Worth it or not?

[gmac78]

Hello All.

With my engine slowly going back together following headwork, turbo upgrade and associated parts, i have a question regarding adjustable fuel pressure regulators.

Does anyone use them to tweak WOT air/fuel ratio?

I have an ABY and 7A FPR, both 4bar i think, to fit my 3B but really could do with an RS2 one to accompany the chips i have.

However i've been thinking perhaps an adjustable one would be better and easier to obtain , giving me some control to tweak overall air/fuel ratio across the range should they be slightly out of spec for WOT. Not sure yet exactly what injectors i'll be using, either Siemens 3600cc or RS2 genuines.

I'm aware that air/fuel will be adjusted for WOT and idle/cruise conditions but with WOT being the more important of the two to prevent catastrophic failure occurring i'd prefer to have that one in check.

Just wondering what your thoughts are on these and do many of you use them?

Cheers

[Rusty]

It will work but that assumes a constant offset of the AFR over the WOT range, so if it's not steady then you'll still be out somewhere. It's not a proper fix but may work.

[Error404]

I believe Motronic can trim fuel enough to cover the 4bar vs 3.8bar FPR discrepancy on an RS2 tune, assuming the injectors are right. If you have different injectors there is more to consider than just the static delivery rate. The latency and voltage compensation will likely be different so they will be way off everywhere, not just on open-loop WOT. Bottom line, tune properly for the right hardware.

[GazzaG60]

id agree. ecu tuning and adaptatino should take care of things.

maybe on an old carb or early injection car it may help.

[gmac78]

FPR's

Cheers for the input guys, i've been thinking that i definitely need a 3.8 bar FPR to make RS2 chipsets work correctly, the problem with that is i would then need an ABY fuel rail and hoses to accommodate the clip in FPR which i've been reading has it's own fitment issues on a 3B IM. However, if you reckon that Motronic could handle the 0.2 bar difference in pressure i may as well use a 7A FPR with my current 3B fuel rail, far less hassle! Assuming of course like you say, i am using genuine RS2 injectors.

Has anyone else used the 7A FPR regulator with RS2 chipsets and injectors that can confirm air/fuel ratios are within spec on known good chipsets?

As always your help is much appreciated

[domas]

wait wait wait.
is your car 3b or aby?

3b FPR is 3 bar, AAN/ABY/ADU is 4 bar
7a is 3.8bar

So if you want to use rs2 injectors on 3b, you have to lower the pressure to 2.5bar or so.

[gmac78]

Hi Domas,

Yes my car is 3B.

I think you might be getting mixed up, 7A/ABY/AAN is 4bar, ADU is 3.8 bar.

7A FPR bolts in the same as 3B, ABY/AAN/ADU are clip in types and would require a different fuel rail.

[domas]

well please double check that then. because either i've been worng all my life or you are.

I was always sure 7a was 3.8 bar

weird

[gmac78]

Here is a link with some info mate

http://forums.quattroworld.com/s4s6/msgs/21108.phtml

[domas]

sorry for that

time to kill myself.

[gmac78]

he he easy mistake to make.

[silizium]

So are you using RS2 ecu or RS2 chipset made to aby ecu or 3b ecu? Or do you know what kind of hardware that chipset is made for? If not then you really shoud not use that chipset.

[gmac78]

I have several options to try. First one is RS2 chipset by Harmmon for 3B application, the other is RS2 chips by TS tuning for ABY ecu, coil packs etc which i will be trying second to compare the difference.

The plan is to convert to ABY ecu etc and leave it at that but since i've got chips for the 3B setup i will try this first before upgrading ignition system. Just trying to suss out the best option for FPR's.

Cheers

[silizium]

Do you know what injectors are those chipsets made for? I thought there was some reason you cant use original rs2 injectors on 3b/aby/adu ecu? And you are planning to use rs2 injectors?