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Fuel system questions

Steve Lovelock - 3/9/06 at 11:51 AM

I am at the stage where I need to sort out the fuelling to the bike TBs I am using. I had planned to use a normal pump to prime a VW Golf GTi pump and feed this via a pressure regulator to the TBs. However I re-read the Luego build manual this morning and noticed that they mount a Sierra pump from a fuel injected Sierra under the tank as shown in the picture. This goes to feed the engine via a fuel filter mounted in the engine bay. There is no mention of a fuel pressure regulator or a primer pump. This appeals to me as it would be cheap, easy and take up little space.

I have a few questions as always.

1) Is the cylindrical item to the very left of the pump a pressure regulator?
2) Would this set up be ok for a Megasquirt / TB set-up?
3) What model and year Sierra would a suitable pump come from?

big_wasa - 3/9/06 at 11:55 AM

Its a Bosch unit and they are not cheap. Think from memory its a filter on the end.

They also fit these to Rs turbos xr3i's ect.

Before 1990 ish as after that they put the pump in the tank.

Edit, Ebay Link

[Edited on 3/9/06 by big_wasa]

TangoMan - 3/9/06 at 12:03 PM

With injection pumps do you not need return feed to the tank. I thought the pumps were constant flow and a pressure regulator sent to excess fuel back to the tank.

I am considering switching to Fuel injection but was considering pumping to a surge tank with a pressure switched pump and then using a high pressure pump to feed the injection with an excess return back to into the surge tank. Does this sound feasibe as I don't really want to remove the tank to add a return feed.

It would also ensure no fuel surge problems.

matt_claydon - 3/9/06 at 01:24 PM

The regulator goes in the RETURN, not the feed. It is the fuel in the pipe between pump and regulator that is at correct pressure. Fuel after the regulator is at atmospheric pressure as the end of this pipe is open to the tank which is vented to atmosphere.

theconrodkid - 3/9/06 at 03:31 PM

that is the pressure reg next to the pimp,its a standard seirra one and runs at a higher pressure than bike tb,s,my suzuki ones are 43psi,plenty adjustabubble ones on fleabay

MkIndy7 - 3/9/06 at 04:00 PM

Not certain thats a pressure regulator on the end of the pump.

On Vauxhalls with the Bosh Fuel pumps that is decribed as a fuel "dampener" (i presume so its a smooth flow rather than a pulsing of the pump)
and then there is also a pressure regulator on the end of your fuel rail (is there not already one on the end of your TB's fuel rail?)

Mark Allanson - 3/9/06 at 04:52 PM

The bit on the end of the sierra pump is an anti hydraulic hammer device (it is a tube with a spring to take ot the shocks in the fuel system).

It does reqire a return to the tank, and does need a filter between the tank and the pump and between the pump and the fuel rail.

It runs at 50 psi, and come from siera's from the late 80's.
Rescued attachment CapriAxle3.JPG

martyn_16v - 3/9/06 at 06:53 PM

quote:
Originally posted by TangoMan
I am considering switching to Fuel injection but was considering pumping to a surge tank with a pressure switched pump and then using a high pressure pump to feed the injection with an excess return back to into the surge tank. Does this sound feasibe as I don't really want to remove the tank to add a return feed.

The problem with that is when you get stuck in traffic or sat still for a while with the engine idling. With only a small quantity of fuel being circulated round and round past the engine it soon heats up, eventually it'll start to vapourise and you'll have problems. If the fuel is returned to the tank itself it can dump the accumulated heat into the larger volume of fuel in the tank, so you don't have this problem.

Steve Lovelock - 3/9/06 at 08:54 PM

One of the things that puzzle me is that the GSXR 1000 TBs I am using do not have a pressure valve on the fuel rail. It has just one pipe to the injectors which means that I need to locate a pressure valve elsewhere in the system. This was one of the attractions of the Luego set up in that it seems to be pressure valve free.

zetec - 3/9/06 at 09:12 PM

I've run a Vauxhall SRi injection pump mounted below the tank. The fuel routes from a small sump in the bottom of the tank via 12mm tube to a pre pump filter, out in 12mm tube to the pump inlet, out the pump in 8mm rubber tube to a section of 8mm copper along the tranny tunnel this connects to a short rubber tube in and out a Vauxhall Carlton post pump filter and on to the fuel rail, out the fuel rail and in/out presure regulator and 8mm back to the top of the tank. No lift pump or swirl tank...was just fine when taken round Brands and Donny.

I've never had fuel starvation issues and keeping the fuel system with new filters (not old ones off a donor) keeps the pump happy.

matt_claydon - 4/9/06 at 07:23 AM

quote:
Originally posted by zetec
The fuel routes from a small sump in the bottom of the tank

...

No lift pump or swirl tank...was just fine when taken round Brands and Donny.

A swirl tank is only needed if you don't have a sump in your main tank. It's just to stop fuel starvation / loss of pressure during hard cornering but a sumped tank has that built in.

As an aside, carbs need effectively the same setup to avoid surge but they incorporate it as the float chamber so temporary starvation to the pump will not result in a loss of fuel to the jets.