To surge tank or not to surge tank?

[joostvdw]

Hello all,

I'm investigating the possibility of getting my 2 stroke motorcycle to run on triple ITBs instead of carbs (I hate them with a passion) and I've sorted almost everything, but I'm not sure what to do on the fuel pump/pressure regulator/surge tank front.

As it is now, it has a fuel tap and gravity feeds the carbs, obviously that's not enough for the injectors who run on 3bar of fuel pressure. I can get a 3 bar fuel pump from ebay (or the scrapyard) and simply run it like this:

Tank/fuel tap -> pump -> injectors

I really like this setup for it's simplicity and I can easily put in a 5bar pump and regulator if I'd wanted a higher pressure, but I have a feeling it won't work.

I could also use a surge tank (like on most FI swapped cars) but since I have a space restriction, I'd rather not:

Tank/fuel tap -> surge tank -> pump -> injectors -> surge tank

And finally, a bit daft, but thought I'd throw it in here anyway:

Tank/fuel tap -> one-way valve -> pump -> injectors -> inlet of pump

This would use the fuel lines as a tiny surge tank, but I'm not sure it would work...

Your thoughts?

Have a picture

[andyborris]

Surge tank is pointless without a pump to keep it full, all it'll do is reduce the natural head for the pump, bit like lowering the water tank in your loft!

I'd try just feeding the EFI pump straight from the tank, but try using larger fuel lines....even if they go up a size then down again.

[jrevillug]

If you vent the top of the surge tank to the fuel tank, the head will remain the same, but there will be a bit of reserve to keep the fuel flowing when cornering.

My friend has an injected Honda Shadow 750 that has a fuel pump in a 'pot' under the seat below the tank. The return runs into the pot, and there are two lines to the tank - one large feed from the bottom of the tank and one small vent to the top of the tank.

[joostvdw]

Mar 29, 2012 15:49:49 GMT andyborris said:

Surge tank is pointless without a pump to keep it full, all it'll do is reduce the natural head for the pump, bit like lowering the water tank in your loft!

I'd try just feeding the EFI pump straight from the tank, but try using larger fuel lines....even if they go up a size then down again.

You mean my first option? Does the pump shut off when it reaches a certain pressure? Is it harmfull for it to pump into a "dead-end"?

Maybe my fuel pressure regulator has a return line, plumbing that into the tank might be the easiest option.

[andyborris]

A surge tank works when it's at pressure, either from a pump or by gravity. The return from the fuel regulator usually feeds into this tank and it has an overflow back to the main tank.

I doubt you've got the room for all these gubbins in a bike frame, so I'd just go with a direct feed to the pump and then return back into the tank, a return is essential, most pressure regulators are designed to work this way, unless you can find a bike one which is a "dead end", I think they're quite rare.

The Yam R1 system I had, did have a return, but no surge tank.

www.megamanual.com/index.html is a very helpful site, even you're not using a MS

www.sdsefi.com/tech.html as is this site.

Good luck

[ianboyd]

well non of my FI bikes have surge tanks, all have a return to the tank, even the new Royal enfields that we sell at work

Bikes don't corner the same as cars, which means fuel starvation is not an issue when cornering,

[HARDCORE]

Locking as non car-content (sorry ) hopefully you've got the answers you needed anyway