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fuel lines, taps, FI pressure and central heating pipe
MikeR - 30/10/04 at 02:24 PM

Folks,

Just got myself 10m of 8mm central heating pipe to make my fuel lines. My plan is to either bend or solder connections but........

I've also bought 2 cut off taps. These are compression fittings. The guy in the shop said he'd expect these to be ok on low pressure. Now for my initial Carb setup i'm expecting it to be fine. Anyone know how much pressure a FI system uses and if these would be ok?

zetec - 30/10/04 at 03:11 PM

The output side of your injection pump to the fuel rail will run at about 45-55 PSI (3-3.5bar) after the regulator the presure is very low as it is just flowing back to the open tank or low presure side of a swirl pot. The presure into the pump will also be low with just the presure of the head of fuel in the tank or 3-4 PSI from a feeder pump if using a swirl pot.

I'm not sure where you will be fitting the taps. If they are to turn off the supply to the injection pump they will not be under anymore presure than for a carb setup. I don't see why you would but I would never fit one on the high presure section.

I'm not sure if normal plumbing taps or valves are OK with petrol.

MikeR - 30/10/04 at 03:26 PM

the plan was to put them in a position so i could turn off the fuel, make changes and turn the fuel on without having to drain the tank. The plan is also to run a swirl pot in the tank and high pressure (when i move to FI) in the full system so i don't need two pumps. Looks like the fuel taps where a waste.

Oh, the taps are all stainless steel and copper so i don't see any problems with the fuel reacting with them.

zetec - 30/10/04 at 04:03 PM

You could go for a baffled tank (as I have) and run from the bottom of the tank to feed your carb pump. Then when you switch to FI just change the pump and connect a return. That way you can still have a tank tap and easy changeover if you do convert, and no need for feeder pump. Just remember to fit a decent filter on the FI pump feed as they block easy.

MikeR - 30/10/04 at 04:23 PM

well my webber carb needs a return anyway so i've got to plumb that in from the start. I wanted to be able to stop the fuel so i could do filter swaps, engine changes, anything really with greater ease.......

ok, so it just seemed like a good idea!

mangogrooveworkshop - 30/10/04 at 07:19 PM

quote:

Oh, the taps are all stainless steel and copper so i don't see any problems with the fuel reacting with them.


The problem is not the metals they are made with but the seals that keep the liquid in its rightful place. Modern fuels have all sorts of chemicals that soften or attack plastics. If a tap is designed to carry petrol this will be taken in to consideration. If its designed to carry hot water then materials that withstand heat and pressure would be used.........????????.

They may do for a time till the seals go hard and crack springing a leak and a fire. Would you tell the insurance guy looking at the car that these are designed for C/Heating and not petrol.

Ask any lads who have had plastic tanks split after a few days with fuel in them ......but thats a whole differant post

MikeR - 31/10/04 at 01:01 AM

I did wonder and worry about this but ........ these taps don't have any plastic in them, the seal is a metal ball with hole in it. Turn the ball one way and liquid flows, turn it another and it doesn't. I'll check my leaving a tap in petrol till i'm ready to use it (if i ever do use it) the rate i build it will either spend 6 months in its petrol bath or 6 hours ..........

yeah ok, 6 months!