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fuel pressure regulator question
omega0684 - 19/2/09 at 03:53 PM

how does a fuel pressure regulator work? i have a small one on the end of the fuel rail on my R1 TB's which has a vacuum pipe linked to it? i have no idea what my fuel pressure is and im using a standard bosch high pressure pump but i dont know what the pressure in the fuel rail is.

what fuel pressure should i have?

vinny1275 - 19/2/09 at 04:09 PM

Hi Alex,

Not sure about R1, my GSXR TBs are 43 psi (about 3 bar), they'd be roughly similar I guess...

Is the regulator part of the fuel rail? In the Suzuki it's a part of the pump, so I had to get an aftermarket one and fit it - this came with a take-off port for a gauge. If it's part of the assembly as it came off the bike though, it should be correct (unless it's a duffer of course)....

Cheers


Vince

omega0684 - 19/2/09 at 04:30 PM

the fuel regulator is at the end of the fuel rail

clairetoo - 19/2/09 at 04:39 PM

You really do need an adjustable regulator if your fuel system is a bitsa - the standard one will have been set to the bike pump .
Dead cheap off ebay - mine was £25 (with a fitted guage) .

clairetoo - 19/2/09 at 04:45 PM

Here's the one I have - bit more expensive , cant find any cheap ones (LINKY)

britishtrident - 19/2/09 at 06:21 PM

quote:
Originally posted by clairetoo
You really do need an adjustable regulator if your fuel system is a bitsa - the standard one will have been set to the bike pump .
Dead cheap off ebay - mine was £25 (with a fitted guage) .


Actually No
To explain a bit provided the fuel pump isn't grossly over sized the regulator will govern the fuel pressure down to 3 bar or so nearly every modern injection system works at roughly 3 bar above inlet manifold pressure .

How a traditional injection system fuel pressure regulator works is it bleeds off fuel from the rail and sends the excess fuel back to the tank when the fuel rail pressure exceeds manifold pressure by more than the set pressure.

This system is reliable and keeps the pump and the fuel in the fuel rail from getting too hot when stuck in traffic in high ambient temperatures.

The most modern tin top systems tend to have the regulator built in to the in-tank fuel filter. which isn't so good but saves the manufacturers as few pennies.




Of course the type of add-on regulator you can buy for carb systems are different again, they don't have a return line so work by regulating the fuel pressure down by continually shutting it on and off ---- this really isn't a good way to control pressure.

BenB - 19/2/09 at 07:03 PM

It'll be a 3 bar sensor as that's what 99% of stock cars work at. The vacuum pipe is because you want the fuel pressure to be relative to the pressure inside the plenum. Otherwise if you ran the fuel line @ 3 bar absolute if you had a condition where you had 1 bar vacuum inside the plenum you would effectively have 4 bar fuel pressure and you'ld crazily over-fuel the engine. Equally with forced induction engines if you had 3 bar pressure inside the plenum you'ld have effectively zero fuel pressure.

IE the vacuum line makes it a relative pressure regulator.

There are lots of adjustable pressure regs on Ebay like the one shown. It may say its made from 6061-T6 ali but the one I've got it blooming heavy and doesn't look like ali to me!!!

If you're not going forced induction stick with the bike one. It'll be fine.... If you're going FI it might not cope with big boost (if its only designed to take vacuum down the line)....