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EFI Conversion fuel flow

r1_pete - 29/5/14 at 05:24 PM

Now my E Type is back on the road I want to get on with prepping for EFI next winter.

I really don't want to run a return line, and modify the fuel tank etc. etc. so I've come up with the idea below:

Fuel flow

The stock SU pump feeds a swirl pot in the engine bay, with a float arrangement to cut the fuel when the pot is full.

I've an in tank pump to fit into the pot, feed the injectors, then return to the pot via the pressure regulator.

Does this look like a workable solution?

Cheers.

Pete.

[Edited on 29/5/14 by r1_pete]

coyoteboy - 29/5/14 at 06:44 PM

Yep, but only if your LP pump can out-flow the HP pump at almost all times and you will almost undoubtedly see quite high temp increases at low EFI flow rates - this is normally negated by the large tank volume and long pipe flows- consider passing the fuel through a cooler on the return.

My biggest concern is venting and how you're going to achieve it without A) starving the pot and b) risking spillage.

r1_pete - 29/5/14 at 07:25 PM

Thanks, I hadn't thought about heat, thats probably enough to justify an extra line and a more conventional setup....

matt_gsxr - 29/5/14 at 08:13 PM

Adding a return line is a good idea really.

In the design you show there are a couple of problems
1) return line from fuel pressure regulator is pressurised so you won't get stable fuel pressure
2) if you run out of fuel then I don't know how you will get the air from the swirl pot
3) fuel temp (but you already knew that)

I wish I was building an e-type. Very jealous.

If you do want to minimise plumbing then I don't see why you can't run a dead-head systems (i.e. fuel pressure regulator next to swirl pot near tank, and just one line to the injectors with no return line). People worry about dead head, but several BMW run dead head as do suzuki motorcycles. Just a thought.

mark chandler - 29/5/14 at 08:47 PM

I tried that, it failed to work

The EFI circuit became a closed circuit, pump cavitation means that over a period of time the swirl pot empties itself and you stop.

matt_claydon - 29/5/14 at 09:30 PM

quote:
Originally posted by matt_gsxr
If you do want to minimise plumbing then I don't see why you can't run a dead-head systems (i.e. fuel pressure regulator next to swirl pot near tank, and just one line to the injectors with no return line). People worry about dead head, but several BMW run dead head as do suzuki motorcycles. Just a thought.

Yep, like this:

Feed only injection fuel sys

The tank, pump and reg can all be at the rear of the vehicle. It works, but I assume there are downsides as otherwise OEMs wouldn't bother with the 2-line systems fitted on pretty much every production car.

The obvious problems are:

*Difficult to vacuum-reference the regulator
*Pressure drop along the feed line means the pressure at the injectors is not exactly what the reg is set at. The difference will vary with flow rate.

Both of these should be able to be compensated for in the mapping though. OEMs have a lot more to worry about in terms of getting perfect fueling for emissions and fuel consumption reasons than you do.

r1_pete - 29/5/14 at 10:04 PM

The Dead Head system could be quite neat, the fuel tank has a small sump in the bottom, so if I use the subaru pump in the tank, the reg in the boot, I wouldn't need a swirl pot, and 10mm pipe would minimize pressure loss, and as its regulated have less pressure in the rear to front pipe.

Thanks guys, that could really work out nicely, and be less fussy under the bonnet.

Uphill Racer - 29/5/14 at 11:18 PM

Why not tee the return in before the low pressure pump?