I am converting my 73 1303 (super) beetle to a watercooled Alfa Romeo boxer engine.

This engine has fuel-injection (Weber IAW). Now I am going to install the fuel lines. I was thinking of this setup, but I am wondering if it will work, feel free to comment on it:



Note the 6 mm outlet of the tank. My tank has a welded on 6 mm outlet which isn't easy to change to 8 mm (or higher).

Let me hear what you think.

Greetings,
Gerrelt.

On light throttle you will circulate hot fuel which will hurt performance, you also risk trapping air in the 'closed' circuit.
You will probably get away with the 6mm outlet your engine, but I would fit the return somewhere else, maybe into the filler neck..
Rich

I think the 6mm line at the tank will cause a restriction regardless of line size upstream.

Run 8mm new rubber lines from front to rear no probs put them inside the tunnel

Also increase the outlet size out of the tank, to the LP filter and pump 12 or 13 mm would be good find another tank if the outlet has been welded in

and as per above run the return line to the filler neck in 8mm

whats the Pulse Damper do ????

Pulse damper, from what I know, takes out the pressure spikes caused by the injectors. Kinda like fitting an accumulator to your water tap to take out water hammers

Nuthing wrong with those fuel lines

What throttle body are you using

Remember that 6mm isn't just a little smaller than 8mm. The cross-sectonal area is about half as much, which might be a problem if fuel is sent back to the tank. Even though the engine gets better mileage, the flow through the pump will be several times the consumption of the engine.

The best approach is to have correct fittings brazed onto the tank. All appropriate precautions relating to welding fuel tanks apply of course. I'd braze NPT nuts onto the bottom of the tank so that you can swap outlets as needed.

If you would rather not do that, then you could run a fuel header tank as recommended by the SDS EFI folks. You need a 1 liter or so tank with two fitting on top and two fittings on the bottom. Feed one of the lower fittings from the tank through an ordinary low pressure electric fuel pump. One of the upper fittings is used to return fuel to the tank via the filler vent. The other lower fitting feeds the high pressure EFI pump, and the other upper fitting takes the EFI return. Size the fittings appropriately to match the tank outlet, etc.

This way, the fuel stays cool because it is being recirculated to the tank, but the capacity of the 6mm outlet isn't being exceeded. If you temporarily exceed the capacity of the 6mm outlet, the level in the header tank drops to satisfy the engine's need for fuel flow.

It's kind of Rube Goldberg, but this would get you around the need to braze the tank.

Untried, but also a viable idea would be to put a heat exchanger in the return line for your "Y" arrangement. Heck, even your long return line might provide enough heat exchange to do the trick. I don't know what this setup would do with air bubbles, though.

George

There are a few problems. The hot fuel recirculating will definitely be a problem, trust me, I had a similar set-up with a surge tank where your Y piece is, and it overheated the fuel recirculating. It looked like this;


You may want to read this thread;
http://forums.aussieveedubbers.com/viewtopic.php?tid=9938

Also, never ever put a fuel filter before a high pressure pump. It will cause cavitation in the pump which will damage it. You should only ever use a strainer on the suction side of a HP pump (like a mesh).

You need to do what others have mentioned and add a small surge tank. You can then use a LP pump to recirculate the fuel back to the main tank, you can then use your 6mm outlet and return to the filler neck or similar. My current set-up looks like this;

sorry to tell you this, but with vibration copper work hardens and becomes brittle over a period of time. Eventually it splits and I think you can imagine what happens. You'd have been better using rubber fuel line than that. When the car is finished and you have some money, pic up some stainless steel or aluminium high pressure pipe in the same diameter and replace those lines.

Maybe rubber rings would help but for the price of some aluminium fuel pipe I wouldn't risk it. I looked into copper early on and came across some horror stories. If those fuel lines crack while driving any leakage could be blown back to the hot end.

woah, hold on a minute.

this is my setup, do you think there could be a problem there?

tank --> generic fuel filter --> facet low pres pump --> surge tank --> hi pres pump --> EFI fuel filter --> motor.

Should I put the generic filter after the facet pump?

A facet pump is positive displacement and isn't as sensitive to inlet restrictions as HP pumps. It won't care too much.

I run a rebuildable mesh strainer on the suction to my facet pump. You buy them from autobarn or anywhere, it's a little mesh screen. Just enough to keep the rust flakes from the tank out of the facet. The facet has a magnet in the main mechanism, and it attracts the rust flakes. They then build-up inside and make the sliding piston part seize (I know from experience ).

Yeah Wes

They appear to be the hard type plastic not the soft stuff used on carby engines and the filter looks like a paper type substance not metal mesh. I had this on the Audi 5+5 straight out of the tank and into a plastic type fileter then into the HP pump and into a HP steel type filter

Same as the 76 Bay window Kombis

the copper will work harden thats why your not allowed to make brake line out of it. Replace them with rubber flex hose its about $50.00 for 8 meters from Pirtek

when I first read about the copper hardening I presumed it was some reaction with petrol - ive never heard of this with brakes too....

here in the Uk its acceptable and legal to have copper brake lines - in fact it is considered preferable by some....and many kits are sold in copper by automec and similar. ive never come across this being a bad thing to do. Im interested to hear more bout this work hardening of copper as I have copper lines on both my van and my morris minor!! why does it harden? is it a reaction with certain fluids?

As you work a metal like Cu it hardens. Vibration of the fuel line or pulsations from the pump will cause this hardeneing of the line. As the hardening progresses strenght increases as does brittless (you can see this difference in hard drawn compared to soft drawn Cu pipe). Work hardening is a mechanical process, put some soft Cu pipe in a vice and bend in back and forth. Its easy at first but gets hards as you go, until the pipe just breaks in half.

[ Edited on 21-7-2006 by mackaymanx ]

Dunno if you guys are interested but there's pictures of my modified '78 Bay tank (and some of my conversion) here:

http://www.vwkd.co.uk/bb/viewtopic.php?t=228 

Rich,
Brake line in the UK is made of CuproNickel, the nickel content makes a big difference to its strength and resistance to work hardening..
Rich

I did a test with my copper tubing. I put a piece of it in a vice and then bent it all directions. It didn't crack.
I had to really clamp it in the vice because it came out. This flattenend the end of it. And, after a lot of bending
it back and fort it finally broke.
My gut feeling says it broke a little earlier than an iron pipe would. But it took a LOT of bending to get it to break.
It was a lot more bending than what these pipes would endure when mounted under a car.
Add to this that these pipes are sold as gas-lines (the stuff you cook with, not the fuel) for campers and
caravans. Campers and caravans vibrate a lot, I can't imagine that these lines would be allowed to use as
gas-lines when they have a habbit of breaking.

Now, my project. I finally decided on this setup:


The pump should always have enough fuel because the 6mm tank outlet only has to provide the used fuel. Which
should be even less then with the original VW engine.
The only problem which could be encountered is fuel
warming up. But, the fuel doesn't spent much time around the engine, so it doesn't really get the change to
warm up (the fuel rail is also isolated with rubber). Furthermore, my copper fuel lines will act as coolers.
But I will monitor the temperature.
This is how it looks like in the nose of my beetle:

As you can see it's easy to check for hot fuel, I just have to open the front decklid and feel the 22 mm pipe.

Some more text and another picture on this site.

More text an pictures on my fuel lines here.

Thanks for all your thoughts and suggestions.:thumb

Greetings,
Gerrelt.

[ Edited on 9/8/2006 by gerrelt ]

[ Edited on 9/8/2006 by gerrelt ]

Copper work hardens over time ... it dosent have to bend as you have done in your testing precudures

Gerrelt,

At my first attempt, I ran almost the same set-up as what you have shown there, but I had a surge tank where you have the 22mm pipe. It looked like this;



It didn't work. After about 40 minutes the engine would start cutting out because the fuel going around and around got too hot. I think without a surge tank you will notice this problem earlier.

That's my experience anyway...