im working on a FE3N+Holset setup. My goal is 500hp-ish to the wheels in my Courier. i have a DW400 pump on the way, an aeromotive FPR, Flex Fuel sensor on the return side and running 3/8 fuel line an ebay fuel rail and 1000cc 5.0 motorsports injectors. It is already plumed as a return system and i was planning on putting the regulator under the hood but there is no good hiding place up there. Now im planning on putting the regulator back by the tank.

If i put the regulator back by the tank should i just run returnless? is there an advantage to keeping it a return system over going returnless?

here is what im working with:

 

I prefer a return system for a couple of reasons...

A return system is constantly flushing itself. Any particle that may have escaped the filter will more than likely return to the tank rather than clogging an injector, and,

If the vehicle sits for extended periods, you will be flushing the stale fuel away from the injectors before you crank the engine.

 

There isn't even a question, return and no other option. Esp for your particular setup.
There is a zero percent chance your setup will work return-less.

 

Just run RTA and profit...

 

Thank you for the input, I'll post pics in the build thread when done.

 

I'm going to be a somewhat dissenting voice and say that while return is slightly better it doesn't really matter all that much. Non-return works fine on my car with 350ish rwhp on race gas, I don't see why it wouldn't work similarly for 500 rwhp on E85.

OEMs use returnless because it doesn't heat up the unused fuel, which helps with evaporative emissions. This is a minor disadvantage in our sort of application because that fuel doesn't cool the injectors back down as rapidly on a heat-soaked restart (drive it, park for 10 minutes, then restart). That throws off the dead time, so it idles a bit lean for a couple minutes in that situation (at anything more than idle the change isn't enough to matter). Returnless also needs a pulsation damper. Other than that it really doesn't make much difference, and I would go with whatever packages better in your application.

--Ian

 

500whp on e85 is a metric ton more fuel than 350 on race gas.

 

Generally, a return system has a referenced rail pressure and a returnless system has a fixed pressure. A referenced system is preferable for a higher boost build.

 

OEM ones, yes, because the regulator is in the tank.

Aftermarket regulator isn't going to be in the tank, so there's no reason you can't just run a long vacuum line back there to reference it. That's what I do on mine.

--Ian

 

OK, we thought there were (2) choices being discussed, when there were (3).
Normal presumption is Returnless = atmospheric reference and Return = manifold reference.
I suppose the other issue is when are pulsation damper(s) needed / not needed?

 

Returnless == atmospheric can only be presumed to be true if someone is using a stock NB fuel pressure regulator in the tank. Given that the project in question is an FE3N in a Courier, I doubt there's a single stock Miata part involved.

I'm not an ME, but my impression is that the pulsation damper is needed whenever there's a significant lag between the pressure changes due to injectors open/closing and the response to that change from the regulator. That lag gets larger the farther the regulator is from the injectors, which suggests to me that you'd need it whenever you have the regulator back by the tank, regardless of whether there's one or two fuel lines going up to the engine bay. I haven't actually tried it, though.

--Ian

 

Im running a stock miata CAS on my FE3N lol