Nice little factory swirl pot / cache tank

gerrelt

On a german vw beetle site, somebody asked a question about this "cachetank":

It's meant for some VW Golf convertibles that were equiped with a fuel injection system.

See:

It's actually a small swirl pot. In the Golf a small in-tank pump delivers fuel into it. One hose attached to
it will be the return fuel line that comes from the engine. The fuel hose on top will provide a fuel return
hose to the tank, for the small fuel pump. And there is this larger outlet that goes to the main fuel
injection pump.

I think this is an ideal and cheap alternative for a swirl tank. They sell for about 20 euros (listed
wrongly as "fuel filter", btw). The VW part number is: 533201511A .

Once I got my other projects done, I am going to use one of these for my beetle.
This is how I would connect it:

The great thing is, that this thing offers a way to convert your beetle/bus to fuel injection without
having to modify the fuel tank!

And you don't have to worry about running out of fuel in a corner.
The only drawback I can think of is the fuel heating up, but as my fuel lines run under the car all the way
to the back and back to the front again, I think the fuel will get enough cooling.

Apparently, the black hose is 6 mm (would be perfect for a VW beetle tank outlet), the blue hoses are 8 mm,
and the fuel pump outlet is 10.22 mm.

The german thread: LINK
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Kai · Posted: Wed Mar 03, 2010 11:06 am Post subject:

That looks pretty sweet and would be a nice clean item to have fitted.

The only problem I can see with it is that I doubt you could use it for the high HP engines i.e. Subaru motors.

The reason for this being that my fuel pump requires a 12mm outlet from the tank. Which admittedly is gravity fed. If the unit is only allowing 6mm outlet it wouldn't suffeciently supply a GRAVITY fed pump.

I realise that there are people out there whom will disagree with me on this who are succesfully running 6mm fuel lines supplying a gravity fed pump but from my knowledge the fuel outlet should be enlarged according to the supply required by the pump, its better practice.

I realise the golf is using a lift pump to fill the pot before it goes to the main FI pump. To use this in a conversion I think you would have to replicate the system exactly (With a lift pump) as it is in the golf for it to be a success

But then also if your not prepared to modify your existing tank to suit your conversion your still running the possibilty of fuel starvation by not fitting any form of baffle into your tank.
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gerrelt · Posted: Wed Mar 03, 2010 7:46 pm Post subject:

Hi Kai,

I have to disagree with you.

You are talking about a 6 mm outlet, but I think you mean the 6 mm inlet from the tank?

The 6 mm inlet combined with the return line should supply sufficient fuel for the fuel pump.
BTW, the fuel pump outlet is 10.22 mm.

The Golf uses a extra pump to feed the cachetank because the FI pump and cachetank is not situated below the fuel tank. It all sits besides the fuel tank, thus causing the need for the in-tank pump.
In this picture you see the fuel pump, it's the black square thing with the silver round thing in the middle:

The fueltank is on the left.
I think it will work without the extra pump, as long as you place it all below the fueltank.

When using this cachetank, you don't need any baffles in the tank. That is what the cachetank is for. I've read on a german Golf forum that people added the cachetank to solve fuel starvation on fast cornering.

The Golf that was fitted with this kind of cachetank had a 1800 cc 100 hp which means it's not only suiteable for low HP engines.
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Kai · Posted: Wed Mar 03, 2010 9:11 pm Post subject:

In is in and out is out in my opinion. The output of my tank which is supplying fuel into my pump is (dare I say it) ID of 10mm od is 12mm

Ok yeah Reading it again for the forth time I realise I've missed the bit where you've clearly explained it does infact have a larger outlet for the FI pump.

However I'd still be concerned about recircating the fuel as you mentoned. Also my pump is a performance pump and is capable of producing silly (sorry I can't remember the actual figure) pressure for the fuel. My concern would still be of restricting the flow. Like sucking a drink through a small bore straw. Although you have got two small bore straws in this case.

One thing we've overlooked is our front mounted fuel tanks and rear engines is similiar to the golfs layout of front engine and rear mounted tanks. So I guess the problem of recirculating the fuel and warming it up might not be worth mentioning as I'm sure vw have done plenty more testing on the idea then any of us sat behind our monitors. I'm sure that if there is a risk of heating the fuel then there would be a fuel cooler plmubed in the systems.

I still wouldn't use it though.

It's cheating.
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gerrelt · Posted: Wed Mar 03, 2010 9:20 pm Post subject:

lol!!

Yeah, sorry..

But you've got a point about the fact the Golf has the same length fuel lines.

I was warned on other forums for the fuel heating up. Baja Wes from Aussieveedubbers had this problem, see: LINK . But he has a big V6 engine in it.
I also might be dependend on how well the fuel rail is isolated for heat in the engine appartment. My Alfa engine has a rubber sleave around the fuel rail, probably because of this.

And, yes, if I would have a high-pressure high-flowing fuel pump, I wouldn't use this also. But for the run-of-the-mill engines, this might be sufficient.
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gazman · Posted: Fri Mar 05, 2010 4:34 am Post subject:

Hey guys, I have a similar setup with a custom made aluminium 'surge tank' as we call them over here Wink

.
You will need a lift pump to fill the tank quick enough to feed even a standard efi pump as trying to gravity feed it through a 6mm hose would starve it. That being said it should be fine for any efi pump with a 10mm inlet as these pumps supply a very high pressure at a relatively low flow rate. In other words its a great idea for anyone using a stock efi pump.
If you have a larger performance efi pump you'll need a surge tank with a matching (or larger) outlet.

We use a bosch pump with a 1/2"(IIRC) inlet and the tank (big silver can thing) has a 1/2" outlet. The Holley Red is the lift pump. Oh and despite high engine bay temps the fuel never gets very hot, possibly due to the large volume of our surge tank.
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gazman · Posted: Fri Mar 05, 2010 4:48 am Post subject:

I've posted this on aussieveedubbers a few times before, a basic pic of how all the hoses etc go on our bus -

Without the Tank Return line, the recirculating fuel would get hotter and hotter and eventually cause problems like bajawes on AVD was having.
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