tom_loughlin
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 posted on 14/6/06 at 01:30 PM |
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Fuel pressure regulator question
Hi guys,
This morning I got myself an in-line fuel pump from a calibra - which should be up to the job - the question is what do I do about the regulator?
Below is a picture of the two I picked up this morning, the one on the left hand side is one from the same calibra i got the pump from (and is
adjustable I think, but only had an inlet and an outlet - As far as I`m aware, I need a return) and has a screw on the top of it.
Does it not need a return?
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The one on the right is from a cavalier GSI, with the Inlet on the bottom, and the feed to the fuel rail in the midle.
What is the top pipe for, it seems very low pressure, as the pipe is not held on with jubilee clips - I`m hoping this is a return feed to the petrol
tank.
Anyway, my question is which should I use for my throttle body setup - ideally, I`ll have Tank -> pump -> regulator -> fuel rail.
Any help will me much appreciated
Cheers
Tom
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Agriv8
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| posted on 14/6/06 at 01:41 PM |
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rising presure Jobbie,
the spare pipe goes to the intake plenum usually
i.e. more vacume in intake plenum - likley to equate to more fuel required. so when vaume is applied it adjusts the regulator for more presure.
Oh might be wrong but the ussual way to connect is
high presure fuel pump to fuel rail / injectors.
other end of fuel rail connected to the regulator
regulator back to tank swirl pot
regards agriv8
[Edited on 14/6/06 by Agriv8]
[Edited on 14/6/06 by Agriv8]
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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tom_loughlin
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| posted on 14/6/06 at 03:10 PM |
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My fuel rail though, only has one inlet port, and no outlet - if its any use, theyre from a gsx-r 600.
I was thinking of using the adjustable one, but im pretty confused as to how to plumb it up.
Cheers guys
Tom
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Krismc
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| posted on 14/6/06 at 03:31 PM |
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i have a adjustable one too and was also confused why there is 3 pipes, but the top outlet mustnt be under much pressure as mine is prefitted with a
very small and thin lenght of blue hose!
Built, Ivaed, Drove and now Sold - 2011 MNR VORTX RT+ 2000cc Zetec on R1 Throttle boddies.
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MkIndy7
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| posted on 14/6/06 at 04:22 PM |
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On the Calibra (the lower regulator) is called a fuel pressure damper or words to that effect to stop the pump from pulsing.
Probably just contradicted myself there as that is kind of what a regulator does.
The higher of the 2 pics is the fuel pressure regulator that goes on the far end of the fuel rail and returns to the tank.
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martyn_16v
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| posted on 14/6/06 at 07:51 PM |
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A bit of misunderstanding about fuel pressure regulators floating about here, so in a nutshell...
The purpose of a fuel pressure regulator is to maintain a constant pressure difference between inlet manifold pressure and the fuel pressure (i.e.
across the two ends of the injectors). The reason for this is to keep the fuel delivery for a given injector open time constant no matter the engine
load. Imagine if your fuel pressure was fixed at 3.5bar absolute. At idle when manifold pressure is low (say 0.5bar) then the pressure difference
between the two ends of the injectors is 3bar. But at full throttle the manifold pressure rises to 1bar (on a normally aspirated engine), so the
pressure difference across the injectors is now only 2.5bar. This will mean that the injectors will flow less fuel than they did at idle. Now suppose
you have forced induction, as the boost keeps increasing the injectors will flow less and less fuel.
Rising rate fuel pressure regulators do increase the difference in fuel pressure as the manifold pressure increases to increase fuel delivery, but
these are basically just a fudge for incorrectly spec'd injectors and totally unnecessary for normally aspirated engines.
For the FPR on the right of your pic, the top connection is to manifold vacuum (hence why it's diddy and is fine as a push on hose), the side
feed connects to the fuel rail, and the bottom feed is the fuel return to the tank (so fuel flows in the side and out the bottom). Fuel is fed from
the pump supply to the rail itself, the fpr then allows fuel to return as necessary to maintain rail pressure.
HTH 
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roadboy
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| posted on 15/6/06 at 11:47 AM |
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If the fuel rail only has an inlet & no outlet it is not possible to regulate the pressure, this means the rail will be under the full pump
pressure, which when I checked mine was 10 bar. This is extremely excessive, you probably only require around 3 bar. You need an adjustable regulator
fitted to a return line from the fuel rail to the tank, or swirlpot if you are fitting one.
Cheers
Ian
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BKLOCO
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| posted on 15/6/06 at 11:53 AM |
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As I understand it some bikes used a non return system, whereby an electric pressure switch was fitted in the feed line from the pump and the pump
pulsed to maintain the correct pressure.
To use a standard car regulator you MUST have a return to the tank and it is in this return that you fit the regulator. NOT the flow line
Experience is what you get when you don't get what you want!!! 
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Krismc
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| posted on 15/6/06 at 06:09 PM |
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could some one draw that one out a scetch or something to clarify- ive had too much sun again!!!
Built, Ivaed, Drove and now Sold - 2011 MNR VORTX RT+ 2000cc Zetec on R1 Throttle boddies.
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JohnN
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| posted on 15/6/06 at 09:58 PM |
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Tom if you look at this ebay item
clicky, it is the same tb's as yours, but as you can see, there are two connections to the fuel rail, one from the pump and the other
goes back to the tank, via the regulator.
If your setup has been re-spaced to match the zetec manifold (as in the above item) you must have a new fuel rail. Therefore, you need to make a
second connection to that rail for the return flow. Depending on what your fuel rail looks like, I or Ian B may be able to help you with the drilling,
threading etc.
ATB John
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