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Ok, I keep hearing everyone saying this is the problem with our cars, and why there is no turbo yet. Can someone please explain to me what a returnless fuel system is, and how it differs from a normal one?

 
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It is exactly what is says. The fuel lines in our cars don't sent the gas back to the tank but use it all up. The old civics used to send the gas back to the tank. The returnless system is supposed to help with MPG.

 
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Oh, as simple as that huh. Exscuse me for being ingnorant, but why does that makes such a difference in a turbo application?

 
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That i don't know. I am new to the scene. Grey would be the man to ask since he has been researching turbos. I think it has something to do with not getting enough fuel to the car to handle the excess air that the turbo is putting in.

 
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Robb you are correct sir. With a returnless fuel system you need to tell the ECU that you are getting larger amounts of air into the engine, so it can send the needed fuel.

 
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if it cant return excess fuel it has to pump it at a lower pressure in order for it to work right...turbos need higher pressure than our system can provide. so if we GIY a return line for the fuel system, and add a higher flow fuel pump, it will work. (except in the state of california)...and HKS USA is based in cali so all their kits have to be legal there first.

 
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good call man. i dont think it would be too hard to do a DIY.

 
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I take it it's the same for Superchargers as well. Both used forced induction so they need higher quantities of fuel, right?

 
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but if there was a turbo, wouldn't we just have to reset the ECM and let it "learn" how much air it's getting?

 
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and if you had longer legs you might be able to run 50mph, not sure if the ECU can make the fuel pump, pump as fast as needed.

 
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Poop is also correct, the stock fuel system could not handle the fuel needed for forced induction.

 
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In a nutshell, you need a properly engineered fuel rail with a return fuel line to the tank, a higher-pressure pump, a rising-rate fuel pressure regulator, and bigger capacity injectors with a modified duty-cycle to work with the turbo. Add to this either a piggy-back fuel computer or a stand-alone programmable ECM. Not quite sure if all this is worth the trouble in a Civic but I AM sure someone will do it.

 
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........
we could upgrade to the RSX fuel pump....
but it's in the gas tank........how the hell do we get it out.........
and if we did upgrade to the RSX......how would the ECU react???.........
Greddy has allready turbo'd the RSX and the Celica has been turbo'd too.
They are both returnless system's....
so how the hell did they do it???........
[IMG]i/expressions/face-icon-small-wink.gif[/IMG]

 
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They may have been able to come up with some sort of fuel map that presicely meters fuel flow/pressure as the engine needs it...theoretically, this is not too difficult since all needed sensors are in place (MAF, TPS, manifold vaccuum) all that would need to be added is a fuel pressure regulator and bigger injectors. A knock sensor wouldn't hurt either...

Edit: This would require precise ECM tuning to tie all sensors into the system and precisely control the fuel mixture...this would leave very little room for error!

 
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The Sport Comapct Car magazine's project Matrix is something we could learn from. Very high comperssion ratio, returnless fuel system, yet they turbo'd it and did it damn well (it survived the trip from Cali to Houston). It's in the May of June issue I belive, or search thier web site here.