Short EFI return system?

[forcefed86]

Just wondering why my system could not be setup like so.... This way I wouldn't have to use a $140 worth of -8 line from the fuel rail all the way back to the tank.

Thanks...

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[GRAVEDIGGER]

What am I missing here? Your picture still shows it going back to the fuel tank doesn't it? Unless your fuel tank is up front it's still going to have to go back to the tank.

 

[mike96]

i think what he is doing is a makeshift return less fuel system, where his FPR and filter are all the way back under the rear seats with the tank.

what would you use to get your vacuum/boost pressure back to the FPR? that much hose is guaranteed to loose a lot.

 

[forcefed86]

i think what he is doing is a makeshift return less fuel system, where his FPR and filter are all the way back under the rear seats with the tank.

what would you use to get your vacuum/boost pressure back to the FPR? that much hose is guaranteed to loose a lot.

Correct, I just don't see the point in running the uneeded fuel all the way to the front of the car and then back again? Keep the regulator and return line right by the tank.

As far as loosing boost pressure, I don't follow you there. No pressure would be lost. It may take it a tad longer to get there, bt no pressure woudl be lost. It would be no different than a brake line really.

 

[steve]

The 2G 420A do that. The downside is poor pressure regulation at the rail.

 

[GRAVEDIGGER]

The 2G 420A do that. The downside is poor pressure regulation at the rail.

Very interesting! I was unaware of that. Thanks for the clarification.

 

[forcefed86]

The 2G 420A do that. The downside is poor pressure regulation at the rail.

I’m not disagreeing with you, but is there any kind of proof to that statement? Seems odd that the newer OE “return-less” fuel systems would have a poor fuel regulation at the rails compared to there older counterparts? What was the point of going return-less in the first place? (again no disrespect, I honestly don’t know)

 

[steve]

Your welcome to search for references like I did when I was curious. I didn't save any links.

The only reason to use a "return-less" fuel system is cost.

You have already pointed out one shortcoming, time delay. That translates to poor dynamic response and remember it's a two way trip, the signal has to get from the intake to the FPR and then the change has to get back to the injectors. A regulator at the end of the rail can dampen the pressure changes that happen in the rail as the injectors open and close. Hard to do that from a mile away.

 

[forcefed86]

Makes sense to me... thanks!

I also did a little search. Another major reason they made the returnless was to reduce evaporative (EVAP) emissions from the fuel system. In 2004, federal emission regulations required lower EVAP emissions. This, in turn, required a change to returnless fuel injection systems on many vehicles.

It aws worth a shot anyway. I'll just bite the bullet and make the braided line purchase.

 

[jrohner]

Look at how boost spike is created/magnified when the hose is too long or too small. I think you're just asking for fuel pressure issues (inconsistent, or slow response of fuel pressure) with a system like this. Not to mention pressure losses on the line to the fuel rail not being compensated for.

 

[steve]

I just can't see putting braided hose under the car. When I finally have to I'll use bent hardline just like original but larger.

 

[forcefed86]

I just can't see putting braided hose under the car. When I finally have to I'll use bent hardline just like original but larger.

I was unsure of compatibility issues with e85 and alum/ss tubing. Probably be ok with stainless, but it's as much as the braided. It wasn't actually as much as I thought. Summit brand -8 was like 84 bucks for 20 ft.

 

[steve]

Stainless is fine for E85, aluminum is questionable.

 

[sheffester]

What if you have an aftermarket fpr? If I recall correctly, my Aeromotive FPR doesnt have a vacuum line going to it. I am actually researching a returnless system because I have a 15 gallon fuel cell and Aeromotive Tsunami fuel pump.

 

[steve]

If your AFPR doesn't use a reference port it's the wrong one for our cars. As far as I know all ECUs you might see in a DSM, factory or aftermarket, expect the fuel pressure to change 1:1 with manifold pressure.