Fpr

[The Vee]

Anybody know if the FPR on a VR4 is rising rate or is it just a standard as in vacuum contolling lower pressure?
Thanks in advance...............

[Nick Mann]

Pretty sure it is rising rate, but don't quote me. The feed to it goes through a solenoid, so it seems logical that it is a rising rate jobby.

[Gly]

1:1 raising rate
afaik
thats what i replaced it with and car runs as it should

[Wodjno]

AFAIK all Turbo/Supercharged engines require a RR FPR.

[The Vee]

OK thanks guys.
Nick, appreciate the solenoid bit, but all that does is bleed off vacuum under certain conditions to bring it up to baseline pressure as required by the ecu - this infact being one of the reasons for my interest in rising rate.
Glenn, That would sound logical - but not sure it is always so

[The Vee]

On a sidenote;
If the young NJ looks at this - don't suppose your reading of the ecu has defined when then solenoid operates has it? I suspect it may well be for cold start enrichment and when hot starting to purge the system of any vapour locks.
As mentioned above, this is part of my "experiment" with fuel delivery. I have bypassed my solenoid with encouraging results, but need some more miles on it yet! (and yes, I do have all the wideband for AFR readings etc!)

[Nutter_John]

As far as I can tell we have not identifed any tables that deal with the FPR function , but it may be a function of a known table for instance boost , as the ecu does not ever know what the true load is

[The Vee]

OK cheers for that NJ. Guess I could go back to old school (hammer & Screwdriver /pan) and wire up a bulb and relay in parallel and see when it does activate. Hmmmmmmmmmmm!

[Nutter_John]

well if you do get any figures back andy , eg rpm versus on or off then I can search the roms for these . But I suspect that you will only see the bulb on as it will more than likely operate at a duty cycle

[The Vee]

OK mate - it's a work in progress and we all know how quick I am at these things:evilgrin: not! But if I get some results I'll certainly give you a shout.

[Turbo_Steve]

If it's anything like the early Evos, it only really seems to do anything on cold start.

[psbarham]

Andy, are you still running this set up?

If so has it made any difference?

[The Vee]

Yes, still running this way, although have a new fpr ready to fit. Solonoid will remain bypassed. Has it made any difference? hard to tell really but I don't seem to get that smell of over rich at odd times anymore. Certainly on a run it will return some good mpg but round town its as thirsty as ever. If you look at my fuelly charts I think all of those are with this mod, but of course there are other things I've fiddled with too like the V6 throttle body etc.

[psbarham]

I might try this then, Mine went for MOT yesterday and they had to evacuate the workshop while the poor sod tried to get it to pass the emissions test /lol

[Beastlee]

Paul, have you used the wideband to sit at 15.2? I have with mine now and it flies through the emissions test, even when I haven't had time to hammer it.

[The Vee]

That's odd Lee, when mine was set at 15.2 it failed as it would not make lambda and had to put it back to 14.7 for test and it passed no probs. In a way I was quite pleased as it proved my LC-1 to be quite accurate.

[Mr.Salas]

Well I changed my fpr and my pump with a walbro 255 and in 3rd gear I have over fueling. I have a wide band installed, so I can see that the a/r is beneath 10 and car runs bad. So why is this happening, fpr is set to 42 base(without vacuum), fuel pump is hot wired, the only thing is that the fuel solenoid is not connected on the vacuum house to the fpr.

[Mr.Salas]

Fuel reg is a 1.1 aeromotive model

[psbarham]

Just an update on this, I have tried the FPR solenoid bypass for several weeks now, and the difference is huge, If i said 10mpg on short journeys (<5 miles from stone cold) would anyone go :o ? the difference in the mpg is massive, and the difference in the way the car runs is unnoticeable even with the outside temp showing -4
a mod all vr4 owners should do in my opinion.

[swinks]

Well done Paul. Give me some details via PM how to wire and plumb up. :)

[jayp]

Paul, is that just bypassing the fpr solenoid with the vacuum pipe going direct from the tb to the regulator , to give an improvement of +10mpg?
If so that is pretty damn impressice!

Sent from my HTC Desire S

[Wodjno]

Just an update on this, I have tried the FPR solenoid bypass for several weeks now, and the difference is huge, If i said 10mpg on short journeys (<5 miles from stone cold) would anyone go :o ? the difference in the mpg is massive, and the difference in the way the car runs is unnoticeable even with the outside temp showing -4
a mod all vr4 owners should do in my opinion.

So your getting over 30mpg on short journeys Paul ?
My last tankful gave an average of 29.3mpg. But that was a small amount of town driving and 6 x 50 mile journeys, each from cold engine start.
Any increase on this would be excellent, and if its a large enough increase then LPG could be put on hold ? Though I suspect it will still take place, but fingers crossed that this can make such a difference !



Glenn

[Beastlee]

At that sort of MPG increase I'll buy another VR-4! 27.9mpg average in the disesal at the mo and that's with 3000 miles on mostly motorways.

[Wodjno]

At that sort of MPG increase I'll buy another VR-4! 27.9mpg average in the disesal at the mo and that's with 3000 miles on mostly motorways.

I would expect that if 351 miles the car achieved on a tad over 54litres, had have been all motorway driving and longer journeys. Then I would thought the car would have achieved 33mpg +.
If this FPR mod even gives 2 mpg, then that would be 30 - 35mpg easily achievable on good runs. And a 2-3 mpg increase on local driving would see 25mpg+ in town. :beer:

Glenn

[adaxo]

Are you guys have a laugh or something?? 30 MPG?? mine NEVER return more than 20 MPG no matter how carefull driven, actually is 18 for last few fill ups

[swinks]

Adam, you shouldn't drive broken car...:)

[Wodjno]

Are you guys have a laugh or something?? 30 MPG?? mine NEVER return more than 20 MPG no matter how carefull driven, actually is 18 for last few fill ups

Adam

I used to think the very same. Never achieving above 20mpg. Average round 14-17mpg. Down to a low of 9mpg average on a full tank of WOT town driving. And 4.5 mpg average on the Ring.
You will be able to find posts of mine saying the exact same thing your now saying. But there is more skill and concentration needed to make these cars drive frugally, than to achieve a 9 min lap of the Nurburgring.


Glenn

[adaxo]

Adam, you shouldn't drive broken car...:)

I know that, but is hard to find how to sort this out, probably must be send for rehab.:lipseal

[adaxo]

Adam

I used to think the very same. Never achieving above 20mpg. Average round 14-17mpg. Down to a low of 9mpg average on a full tank of WOT town driving. And 4.5 mpg average on the Ring.
You will be able to find posts of mine saying the exact same thing your now saying. But there is more skill and concentration needed to make these cars drive frugally, than to achieve a 9 min lap of the Nurburgring.
Glenn

You probably right, what I find out is, usually when I fill up and then drive around 100 miles till fuel gauge set exact on half way down BUT sometimes after driven 100 miles fuel gauge sit few millimetres above half so me think 'is good result' and then start some full throttle action/rally/pan, after that fuel gauge just plummeting down, and here is 18mpg result/Hissy

[The Vee]

Paul, that's a great improvement - nice one. Certainly, like yours I had no running issues when cold, if anything possibly slightly cleaner and AFRs still good when warm and hooning it! What's more it'll still do the 9mins at the ring :p. (but at a very reduced mpg though!) TBH , mine made more difference on the run rather than round town.

[Wodjno]

Paul, that's a great improvement - nice one. Certainly, like yours I had no running issues when cold, if anything possibly slightly cleaner and AFRs still good when warm and hooning it! What's more it'll still do the 9mins at the ring :p. (but at a very reduced mpg though!) TBH , mine made more difference on the run rather than round town.

By how much on a run did it make ?

[The Vee]

I would think 3-4 mpg. The only thing I cant do is be absolutely definitive as mentioned earlier, I was "fiddling" with other bits as well. But still convinced it does make a difference as that over rich smell at times has also gone.

[Wodjno]

I would think 3-4 mpg. The only thing I cant do is be absolutely definitive as mentioned earlier, I was "fiddling" with other bits as well. But still convinced it does make a difference as that over rich smell at times has also gone.

Ok Thanks.

[The Vee]

another thing I found (slightly off track - but relevent to mpg) is that de-catting does help with performance but on a long light throttle run, I find it's slightly better on mpg with it fitted. I can only guess, that would be down to back pressures, off spool etc etc

[psbarham]

it really is a 5 min job, just run a hose from the fpr to the nipple on the tb.
on a run I would say its worth 1-2 mph, cruising at 56 gives 37 mph.

[Nutter_John]

Whats the AFR's look like when running with this mod in place , as to use less fuel you must be running leaner ?

[Wodjno]

Whats the AFR's look like when running with this mod in place , as to use less fuel you must be running leaner ?

Not entirely correct John

Glenn

[Nutter_John]

I am fully aware that when you fit an aftermarket FPR you by-pass the solenoid , but this is because you set the pressure when fitting it and it then follows the engine correctly ,

So if the stock FPR is not actually rated to 3 bar and say is only at 2.5 and the solenoid up's this pressure to raise the fuel pressure by controlling the amount of air being seen by the stock FPR , remember that also the stock FPR is fixed and can not be adjusted

Anyway If you are allowing the stock FPR to run at the actual line pressure (eg linear with the engine ) then you will not be running the same pressure that the ECU believes will be there - the Solenoid allows the ecu to adjust the actual pressure based on the RPM band .

So therefore if you are running at say 2.5 bar actual fuel pressure and the ecu thinks it should fire the injectors for 33ms then the amount of fuel pushed through the injector in that 33ms will be less at 2.5 bar than it would be at 3 bar , which would mean that you would see the fuel ratio to less as you have allowed less fuel in .

But if the Stock FPR is fixed at 3 bar then it should not realy make much difference or just adding a aftermarket FPR would also show the same traights

[The Vee]

John, the vacuum is connected to the FPR - just direct from vacuum nipple on TB / manifold and by-passing solonoid so that the ECU can't encourage higher pressure when you don't seem to need it.

[psbarham]

the afrs are pretty much the same, maybe .3 lower when cold.

[Nutter_John]

Thanks Paul , do you notice much difference when on full chat ?

[psbarham]

Thanks Paul , do you notice much difference when on full chat ?

none at all tbh, it was bypassed at the rr day so it definitely didn't affect power :D

[Kenneth]

Sounds like a mod I should try... Bypassing the FPR solenoid will also free up an output on the ECU.

/edit: done on my car now. Be interesting to see if it has any effect on warm, open loop idle.

[wintertidenz]

Kenneth - could that FPR output be redirected so we can use the FPR solenoid for boost?