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MG MGB Technical - Racing fuel system design - opinions

Hi,

As some of you may know I'm trying to get my track car sorted at the moment with a new engine. After that's sorted I will be completely replacing the fuel system in the car.

It currently has a standard MGB fuel tank and a Facet Red Top Pump.

The plan is to use a Jaz racing fuel cell mounted in the boot with an internal lifter pump feeding into the top of a fairly large fuel swirl pot. I then want two scavenger pumps feeding off the bottom of the swirl pot, which will have the fuel lines joined towards the engine side of things (i.e. there will be two fuel lines). I know this may seem a bit over the top but I've seen similar systems used time over in many race/track cars. The fuel cell will be fed by a custom pipe/fuel filler which will (hopefully) be mounted somewhere on the side of the car (perspex window maybe)

I would like your opinions and/or designs/systems used in your own track/race cars for comparison.

I would also like some advice on the types and makes of pumps required. I had planned on using two Bosch 044 pumps until I found out how much they are! (about £250 each new)

Thanks in advance everyone!

olly
OT Hayter

O.T. it sounds pretty sound, but I wonder why you plan on using two pumps off the swirl pot and only one to feed in? The swirl pot won't do any good unless the volume in is equal to or greater than the volume out. If the use of dual pumps is for reduncancy, then I'd also use two pumps on the input side for the same reason. Always place check valves in the lines to prevent fuel from returning through a leaky pump valve in the other pump in the event of a failure.
An economical fuel pump might be found at the breakers off of a VW, BMW, or Audi. Most of these used a Bosch high pressure high volume pump which mounts outside the tank on their later injected engines. Downside is that they are designed to work with a pressure relief valve and a return line as used on injecton systems. Hope this information helps.
Bill Young

I have built my own ally fuel tank, baffled, I use blue Holley fuel pump. The engine is a rover 3.5 V8 with Holley carb.
Regards
http://membres.lycos.fr/mgcontact/fileupload/uploads/1131045247_fueltank.jpg
http://membres.lycos.fr/mgcontact/fileupload/uploads/1131045247_fuelpump.jpg
michel

Olly - are you running a fuel injected engine?

If not all the swirl pots and extra pumps are superfluous money and weight.

If you are, it sounds about right.
Bill Spohn

You may want to think about cutting the trunk floor to lower the fuel cell to improve handling. A friend did that and it dramtically improved his handling especially w/a full tank. He used a custom mount with a flange to hold and lower the cell.

A holley fuel pump should serve all your needs providing you're not running an injected motor.
Mike MaGee

Are you 2 pumps/pipes from swirl pot to fuel rail so as to avoid cornering fuel starvation?

If this is the case an alternative is to design the swirl pot to avoid this. A narrow tall swirl pot having a cone shaped bottom with the out let at the point of the cone will do the job. The return line from the fuel rail comes in at the top. Any overflow line back to the main tank goes out of the top.

Unless you intend to spend all day driving round a round about, a swirl pot of 2 litre capacity will be plenty.

You might like to have a quick look at the midget project on the Emerald web site. Dave Walker did not find he needed to go to the extream of swirl pot shape that I suggest.

David
David Witham

When I originally designed the system (in my head that is) I was planning on using fuel injection. As it stands the need for a new engine has prevented me from affording this, so I will be sticking with the carbs for the time being.

If that's the case can I just use a single lifter pump, swirl pot and single Holley fuel pump instead? I hope so as that is cheaper!

The engine is running a twin turbo set up with suck through carbs. I am now planning on changing them to blow through carbs using a rising rate regulator. Will I still need a return line to the tank?

thanks

olly
OT Hayter

Interesting. For blow through the carb you have need a pressurised carb, what carb? (SU HIF44 for metro turbo, for instance, is pressurised, but it's a small carb) I think with a carb, swirl pot and return fuel line it’s not necessary, “just” a good pick-up system with an internal collector and surge tank. With a blue Holley fuel pump, a fuel pressure regulator is necessary.
Regards.
michel

Go simple - you don't need all the fancy fuel injection stuff.

Just use a good high volume pump (I use a Carter Superpump) and an adjustable fuel pressure regulator.
Bill Spohn

Michel,

Yes I had planned on using turbo-specific carbs. I know I can get either Montego or Maestro Turbo carbs - the 1.75" carbs bolt straight onto the SU manifold that I have, so I've been told.

I will be fitting a swirl pot anyway, as I want to run EFI eventually. I just thought it would be cheaper in the long run to buy some good injection pump(s) rather than e.g. a Holley, which would need replacing if I went for EFI.

I now think I can get away with a simpler system. The original design was based on systems observed in fuel injection cars. I don't have many pics etc of a carb-engined racing fuel system.

thanks
OT Hayter

Hi OT,
Consider this for a "Swirl Pot"
http://bcbroncos.com/store/product_info.php?cPath=27_51_108&products_id=119
and how it is used:
http://classicbroncos.com/efi.shtml
Regards
Tony
Tony Bates

Tony - that is brilliant.

Thnks very much, the Bronco fuel solution looks like something I can use in my V6 Jamaican project without changing gas tanks or having to weld in a swirl pot, or having to watch fuel level.

Anyone elese doing such a project would be well advised to take a look at Tony's link!
Bill Spohn

This thread was discussed between 03/11/2005 and 06/11/2005

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