Injection fuelling

[colnagowetdream]

Thanks for the help in sussing out my coolant hose runs (hoses will be ordered tomorrow). The next part of my engine swap is the fuelling.

1. My narrow body has a "carb" fuel tank (from its X-flow days), I know I have to fit a swirl pot  but where in the fuel circuit?

2. Do I have a fuel pump feeding the swirl pot and then another pump taking a suction from there and supplying the fuel rail?

3. Do I fit the fuel regulator before or after the fuel rail

4. What pressure should I be looking for in the fuel rail?

5. Where do I fit a filter(s)?

Thanks in advance

[Blatman]

The order is:

Fuel tank > filter > lift pump (Facet Red Top) > swirl pot > injection pump > another filter > fuel line > fuel rail > pressure regulator (45psi) > return to swirl pot.

Everything before the fuel line needs to be mounted at the rear of the car........ IMHO......

[Kevin Wood]

I have just done a carb to injection upgrade in this manner. Used the Red top fuel pump as per standard carb installation to feed the swirl pot. Fitted a fine filter to the output of the red top and didn't bother with a filter in the high pressure circuit as I figured as long as the system's clean to start with the low pressure filter will stop anything getting in.

Couldn't fit the swirl pot in the rear easily so I have mounted it and the high pressure fuel pump just under the top chassis rail on the inlet side of the engine. Red top feeds swirl pot at a tangent towards the top of the swirl pot. Return to the tank is taken from the very top centre of the swirl pot. I put a 1.5mm dia restriction in this line as otherwise the Red Top does its' nut trying to pump against no restriction. Return to the tank uses 8mm kunifer fuel line, a section of rubber hose to a -4jic bulkhead union I fitted in the top of the tank - near the fuel sender for easy access. I have a section of rubber hose inside the tank down to the bottom to prevent aeration. Maybe not necessary.

On the high pressure side you end up with a very simple circuit. Surge pot (bottom) -> Fuel pump -> fuel rail -> Pressure Regulator -> Surge pot (top, at a tangent). The high pressure plumbing is reduced to a small area on the inlet side of the engine with the main fuel lines to the rear at low pressure.

The swirl pot came from SBD and the pump is a sytec (FSE) Sierra Cosworth equivalent.

I have both fuel pumps powered via a relay from the ECU so they run for 3 seconds to prime when ignition is switched on and thereafter only when the engine is running.

Standard fuel pressure varies with the injector manufacturer but is typically 3 bar (45 PSI ish). You can run injectors at significantly higher or lower than their specified pressure which alters the flow rate but eventually the spray pattern suffers. I used a 3 bar fixed fuel pressure regulator from a scrap Cavalier SRI. Injectors came from a scrap Volvo with roughly the correct amount of power (190BHP). Check the impedance of any injectors are compatible with the ECU you intend to use.

What is important is that you end up with injectors that flow the correct amount of fuel for your engine at the pressure you're using them at.

Fuel pressure regulators should be fitted at the opposite end of the fuel rail to that fed from the pump. This bleeds air from the fuel rail and also provides a flow of fuel through the rail to prevent it getting too hot.

HTH

Kevin