Simplifying Fuel tank/pumps - thoughts?

[greenwoo]

I've promised myself 1 winter mod....and that's to simplify the fuel system on the Tiger.

Currently it runs a 'typical' kit car system for EFI.....tank>LP pump>swirl pot>HP pump and return.

The tank has some crud in it that needs sorting, currently the pick up is from the top and i have 2 plans;
1/ Get a new tank made which would incorporate a swirl pot/sump to do away with the LP/external swirl pot.
2/ Take the existing tank out, get that changed to have a bottom outlet to effectively end up with the same as option 1. Albeit a new tank could prob be made to have more capacity - but that's not essential as it has 8galls+ already.

My question. Why do we have external fuel pumps ( HP ), why don't more kit cars use a pump/system from a factory car?
Having a quick look it would seem that there are many internal pumps that have some form of a chamber to make a swirl pot redundant ( assuming the tank is well baffled). And given that factory cars would seem(?) to rarely need a new fuel pump....that would appear to be a neat solution?

What critical point am i missing? Wouldn't a pump from say a fuel hungry car like a turbo ST or a rover V8 have enough capacity in comparison to the external Bosch that i currently have?

Thinking that if i'm going to have my tank cut to freshen it, to make sure that its well baffled....i could at the same time get them to cut the right size hole in the top for such a pump.

The end result i want from all this is to do away with 1 'circuit' that could/might fail....ie/ losing the external swirl pot/lp pump would be 1 less set of variables/hassles.

Thoughts guys?
Got to make a decision shortly as want to progress this and clearly whilst am dicking around with the tank it makes sense in my head.....

[kenton]

If i were in your situation id go option 1 with the built in sump assuming there is room below the tank without interfering with the diffuser. I like the bottom exit with external pump, its easy to check fuel flow or flush out crap. Its a common set up and if need be there is usually a spare pump carried on road trips.

[leegav]

Yes mark. I had this dilemma on the tiger. I didnt want all the pipework and swirlpots.
I ended up running. Baffled tank with one inbuilt fuel pump and filter. All i had was two fuel lines running through the car. One to feed the injector rail and one return to tank. Only thing inline external of the tank was the regulator.
Speak to pro-alloy. They built my tank and gave me lots of advice and i bet they still have my drawings. My advice if you want to simplify is get one built. Il have a look on my emails and see if i still have the cad drawings they did for the whole thing for me to sign off.

[leegav]

No drawings im afraid but some info in what they did for me..



What are the internal collectors for inside the tanks?

Our internal collectors are a fabricated box which has check valves mounted in the side faces. These check valves allow fuel to run into the collector but not out, so as the vehicle corners, brakes and accelerates the fuel is scooped into the collector through the check valves, this ensures that the collector is constantly full, even when the tank is almost out of fuel. This means that you are able to utilize almost the entire volume of the fuel tank without suffering from surge and pick-up problems, and can often remove the necessity for an external fuel swirl pot.

And this
http://www.proalloy.co.uk/pages/669.htm

You can get inside the tanks through there areo style entry points to clean it out and clean the filter.

[DJ.]

To be honest i'm not sure how it works, but on my Caterham, there is a large plastic pump unit that screws into the top of the tank and hangs down into it. There is only one fuel line to the injector rail, and the pump unit contains a sensor for the fuel level too.

The advantage is virtually no plumbing and the only wiring goes straght to this unit. Here it is on the Caterham parts site:
https://caterhamparts.co.uk/pumps-senders/3000-fuel-pump-module-sigma-suzuki.html

You'll notice the big drawback is the price I hope they are reliable!

[Matth93]

That looks very similar to a Ford Focus one

[greenwoo]

@ Kenton - height/space could be an issue. An R6 tank is already low, whilst i could possibly raise it, it wouldn't be ideal. Starting from scratch would be (in theory) foo proof, it does mean a certain faffing to get the dimensions spot on.
In terms of the 'sump' idea, i'd wondered about raising the internal 'floor' of the tank over say 4/5 of its length and siting the outlet in the deepest part to create a sump.
downside would be a slight loss of overall volume.

@ Lee, yep i'd seen pro-alloy and had wondered about them. Thing is i have no idea whether there's any effective baffling in the existing tank....if there is, or if that could be easily adapted/added to, would be relatively easy - in that i know the existing tank fits.

@ duncan/Matt.....yep that's the sort of thing i was wondering about. I know that the one for high power Caterhams is £'s, but logic ( easy tiger ) says that surely a standard pump for a high powered engine would suffice. Just wondering if there's any obvious issues with that thought?

[ChrisS]

I’m using an Elise tank and pump on my project. Tank is baffled (although lots of folk seem to reckon it’s a poor design and spend thousands on fancy fuel cells) and the pump is simply a stock Toyota item (although it came from an Elise) with integral fuel pressure regulator and level sender. I had intended using a pump assembly from the donor Alfa 166 as it was functionally the same but was just a gnats too big to fit in the tank.

Ultimately the same as above though, one fuel line feeding pressure regulated fuel to a closed end fuel rail.

[jeffw]

You can certainly replace the pump in those OE pump/filter swirl pots, done this in the past by putting Bosch 044R pumps in. In tank pump/swirl pot/level/regulator/one outlet will simplfy the whole set up considerable but you will need a new tank to suit.