Fuel regulator set up

[Emz]

Hi all,

Just looking at installing my fuel system. The reg can be installed in two ways, just wondering if anyone has any comments or advice on which way would be better.

Config 1:



Config 2:


Thanks

[iOnic]

#2 with filter after fuel pump. Use the 3rd port on the reg for a fuel pressure gauge.

[soopachargen]

factory setups usually run like no.2 dont they? the reg keeps the rail up to a constant pressure

[Mr Revhead]

Later systems (altezza avensis etc etc) use system one.
No return from engine bay needed.

[evil_si]

always run the reg after the fuel rail

[Emz]

always run the reg after the fuel rail

why?

[sergei]

and filter after the pump.

[Emz]

filter after fuel pump.

why?

[sergei]

Filter is an restriction, pumps are limited how well they suck. Sucking through restriction is a much bigger loss than pumping through it.

As for the regulator after the rail look at this thread: http://www.physicsforums.com/showthread.php?t=291326

Basically the goal is to make pressure constant on the length of the rail.
The problem if the regulator is before the rail, the pressure drop is uniform a long the fuel rail (assuming the injectors open simultaneously), which means the injector that is further from the pressure regulator will receive less fuel.

If the regulator is after the rail, it compensates for the pressure drop inside of the rail making it more uniform.

[bluemaumau]

and filter after the pump.

dont you want to filter crap so your pump doesnt get wasted

[sergei]

and filter after the pump.

dont you want to filter crap so your pump doesnt get wasted

That is what the strainer is for.
The normal high pressure fuel filter is designed to be pushed through.

[Emz]

Thanks everyone!
Will use config 2 with filter after pump

[stolic]

The normal high pressure fuel filter is designed to be pushed through.

check out her build thread, that fuel filter ( and pump for that matter ) is far from "normal"
fyi manuals for both state the pump and filter can be installed either way, and cos they're both stupidly huge -12an fittings they can be swaped around with little fuss if there's an issue.

[strx7]

On a big power 6 cylinder i'd actually be tempted to feed into the centre of the rail and then have a return from each end, joining than going into the reg.

Diagram 1 only works with variable speed pump config's which is what all the modern japanese stuff does, they vari the pump speed to keep the pressure

[Malcolm]

Diagram 1 only works with variable speed pump config's which is what all the modern japanese stuff does, they vari the pump speed to keep the pressure

not true, used a returnless system on the last 3 FSAE cars, had no fuel pump control and it worked fine.

Should see less pressure drop across the fuel rail too, because you have a lower fuel flow rate along the rail (only as much fuel as is being flowed by the injectors flows along the rail, as opposed to the entire flow of the pump).

IMO the only thing you really lose with the returnless type is that you might have less fuel cooling of the fuel rail, but that is unlikely to be much of an issue. edit: and the fuel would be flowing more slowly/stationary in the rail, so it would have to accelerate more to be injected - not sure on the magnitude of the effects of this either

[matt dunn]

IMO the only thing you really lose with the returnless type is that you might have less fuel cooling of the fuel rail, but that is unlikely to be much of an issue.

Less fuel cooling? no way, returnless systems kick arse for fuel cooling,
as the fuel is burnt before it gets hot.

After a race in my car the fuel tank is hot to the touch because of the fuel getting heated and returned to the tank,
especially bad as the tank only holds 22L.

Preventing the fuel getting hot is one of the main advantages of returnless systems IMO.


The main downside is most have the regulator in the tank at the back,
and so run a constant fuel pressure that does not alter with manifold pressure, which usually makes them unsuitable for forced induction applications.

[matt dunn]

On a big power 6 cylinder i'd actually be tempted to feed into the centre of the rail and then have a return from each end, joining than going into the reg.

Yeah it is a good idea, especially on anything with large injectors.
I actually seriously considered it for the 20V as anything side feed suffers from it quite bad.

Diagram 1 only works with variable speed pump config's which is what all the modern japanese stuff does, they vari the pump speed to keep the pressure

that is usually more to prevent noise rather than flow.