The V8 Owners Forum -

I am currently carrying out a project to fuel inject my 3lt Triumph Stag using 2 sets of Suzuki GSXR 600 throttle bodies
Looking at the fuel delivery side of things, I intend to fit a fuel swirl pot and have the original fuel pump as the lifter pump into the swirl pot, and of course a high pressure pump to feed the fuel rail, then back into the swirl pot.
I do not want too high a flow rate for the high pressure pump or it will just overheat flowing around the ring, but how high?
If I said sufficient for say 200BHP?
The original SU low pressure pump maybe flows only 70 Lt/hr, so surely the popular Bosch 044 pump flowing at 264 Lt/hr would just be silly
Any guidence appreciated!
Thanks,
Mike.

The 044 is a full on motorsport pump and although you could use it, it is a bit much and IMO far to pricey.

For my EFI set up I opted for the next one down (i think), Bosch 910, but I will be running about 300bhp.

Pretty much any EFI pump will do really, but make sure the original lift pump can flow enough to cope.

I'm currently fitting an almost identical system to the one you describe, and was using a Facet Red Top pump but I've now replafced that wil a Holley Blue pump (if it ever arrives!)

The Bosch 910 makes more sense over the 044. 204 lt/min compared to 264 lt/min, and half the cost.
Where did you purchase your 910, I have been looking at www.fuelsystem.co.uk for tech specs and prices.
I assume my original SU pump will be sufficient, its okay running my holley so the power increase will only be marginal going EFI, I am thinking more efficiency
Overheating the fuel though is a worry at idle speed. I guess a certain amount will flow back from the swirl pot into the main fuel tank at idle.

If you are not planning to take the high pressure return to the tank (rather than the swirl pot) then I would do so, this will avoid over heating the fuel (which I think is actually of little concern given the heat capacity of a few gallons of petrol and specifically the latent heat of evaporation for petrol). If you are always bringing fresh pertol to the swirl pot from the tank you will not boil your petrol with a fuel pump.
Mike

My initial thoughts was for the return from the fuel rail back into the swirl pot, and from the swirl pot back into the fuel tank.
I don't know in reality how much fuel would flow from the swirl pot back into the fuel tank though.
I agree returning from the fuel rail straight back into the fuel tank would be the best option, however my low pressure lifter pump would have to be sized bigger than the high pressure pump, something like 4 times bigger than my current SU!

mjheathcote wrote:My initial thoughts was for the return from the fuel rail back into the swirl pot, and from the swirl pot back into the fuel tank.
I don't know in reality how much fuel would flow from the swirl pot back into the fuel tank though.
I agree returning from the fuel rail straight back into the fuel tank would be the best option, however my low pressure lifter pump would have to be sized bigger than the high pressure pump, something like 4 times bigger than my current SU!

This is the better way to run the system.
As at full power the low pressure pump may not cope with moving enough fuel to keep the swirl full (or pump air for a couple of seconds as fuel sloshes in a part full tank) and then the fuel rail stuff will go to the swirl and be recirculated (all be it slightly warmer)

As soon as you are off max throttle the low pressure pump will refill the swirl (if it pumped air) or replenish the swirl with new cold fuel and the warm stuff would be returned to the tank.

So the fittings should be from top of swirl
Exit back to tank (Hot fuel rises)
Return from Fuel Rail
Fill fron tank via low perssure
Draw to high pressure pump filter and fuel rail

Cheers
Ian

Thanks Ian.
Just need to establish the best place to buy my pump & swirl pot at a good price!

There's a place called AH fabrications who I've spoken to. They do a good swirl pot for about £92 + £12 on ebay (cheaper through other places though). The swirl pot has a 8mm feed from lift pump, 8mm return from fuel rail, 6 or 8mm return to tank and 13mm feed to high pressure. Perfect for the system you describe (and for me!). 1.5 litre capacity too.

As for the Bosch pump, well I had to shop around but you can get Bosch pumps that aren't branded 'Bosch' for a lot less than the normal priced pumps. I paid less than a ton for it, including fittings.

Thanks

I got mine from
James Aiken trading as Alloy racing Fabrications 07968 329 108
www.alloyracingfabricaons.co.uk

Price £45.00 plus £3.50 post and packing

Had to pay up front but it arrived within a week

Ian

Im running a 910 pump which supports easily 300hp, Have a look on EBay for a escort XR3i, Granada and capri 2.8i all use this pump.
As for swirl pots and returns, I have allways fed from the swirl pot and returned to the tank as keep feeding the fuel round in a short circuit the fuel absorbs heat, rather than having the fuel in the tank acting as a heat soak, and we all know hot fuel is not ideal.
On my car now, I dont run a swirl pot at all, I just have a gravity fed 910 pump and a decent rear pickup mounted very lowwith a small filter fitted to the end.