EFi fuelling?

[Twitch6284]

Hey guys. 

I am currently doing an engine swap on my '86 Daihatsu Domino. Going from ED-10 engine (carb) to EJ-VE (EFi) one, mostly done just need some fuel system advice.

I was thinking I could use the Domino's tank, with a low pressure lift pump up to a boot mounted swirl pot, out through a LP filter to a high pressure pump then through a HP filter to the fuel rail.
 


All seems to make sense up until the fuel rail, as with this system I believe I would need a return from the fuel rail back to the swirl, and then a return from the swirl to the tank. Is this correct?


But the fuel rail on the EJ-VE has no opening for a return. Only an input. So would I need an aftermarket fuel rail that would accommodate a return line to run the aforementioned system?


And as such I am assuming the ECU would be running the in tank pump (from the donor) on-demand, so would I need to get ECU work done to work with the constant flow of the aftermarket pumps, or could I just wire them in to the original system wiring and run them on-demand, therefore negating the need for a return line?



Not going to lie, I am new to EFi stuff, so apologies if my questions are stupid.. 

[MrSpeedy]

I've only done one EFI install but it was from scratch.

As I understand what you're saying, the in tank pump is the low pressure pump (lift pump) ?!
In that case the ecu won't control that. You'll need to switch that through a relay off of the ignition switch.

As for the fuel rail, it is more common to have a circulating fuel supply, but not essential. I see no reason why you can't tee off the supply to the rail and feed that back to the swirl pot via a pressure regulator.

[Twitch6284]

So I could plumb the return line into the system before it gets to the tank??

This idea sounds odd to me, but I will try and look into it.

Yeah, the in tank pump would be the low pressure one, just on a switch would make more sense.

Cheers dude

[vitesseefi]

If there is no pressure regulator on the fuel rail then it must be built into the pump assembly on the original vehicle. This will also mean that it has no manifold pressure reference connection, so the fuel pressure correction to allow for changing manifold pressure is done electronically in the ECU.

If you are going to use the original ECU then you could keep the original arrangement with an unreferenced pressure regulator somewhere between the pump and fuel rail. The regulator set pressure needs to be the same as the door vehicle and it'll need a return line to the tank/swirl pot if it's not built into the pump. Ideally you'd use the pump assembly from the donor vehicle (perhaps built into a swirl pot if fitting it in the tank is not practical), but this may not be realistic.

If you are going to use an aftermarket ECU then you'll probably need to add a manifold pressure referenced regulator close to the fuel rail and plumb a return line for that. I usually use the original carb feed line for the return and put a new high pressure line in.

Nick

[MrSpeedy]

I understood that you only need a pressure sensed regulator on a forced induction system? Otherwise surely it'll be measuring vacuum in the inlet manifold, not pressure ?! Or am I missing something?

[Twitch6284]

Thanks Vitesseefi. No, there is nothing coming off the fuel rail apart from the input. There is something that I thought was a FPR on the rail but apparently that is a pulsation dampener. Another term that I am not familiar with. But there is no connection of any sort that comes off that.

I hadnt thought of putting the original pump into a swirl pot, that is something I will look into. Although I am considering cutting the original and donor fuel tanks frankenstein-ing them together so I can just use the donors complete assembly. And then just running a new line.

Does it matter if I don't plumb the charcoal canister from the donor back in?

[vitesseefi]

Nov 26, 2015 10:36:46 GMT MrSpeedy said:

I understood that you only need a pressure sensed regulator on a forced induction system? Otherwise surely it'll be measuring vacuum in the inlet manifold, not pressure ?! Or am I missing something?

Pressure sensed regulators were used on most injected cars well into the 2000s. Purpose is to maintain a constant differential pressure across the injector (ie fuel pressure goes up and down with the manifold pressure) to make the ECUs calculations easier. They work on NA applications (mostly below atmospheric pressure) and forced induction where they'll see positive and negative pressures - purpose is the same in both.

Don't see any reason to keep the charcoal cannister though it is possible that the OE ecu will get upset if it can't see any electrical gizmos that may have been attached to it.

Nick

[Twitch6284]

Cheers nick No electrical gizmo's attached to the canister so may just ditch it.