Conversion to Return Fuel System

BosnianLanos · Post by **BosnianLanos** » Mon Feb 12, 2007 11:00 pm

As you guys now, our Daewoos have a returnless fuel system. Older technology, makes it hard to control fuel flow.

Well, with recent upgrades to my intake system (Cold Air, Larger TB, Bigger injectors) and a thirst for some nitrous (the kit is waiting to go in), I'd really like to convert the stock returnless fuel line to a return system. My main motivation is fuel pressure control through a fuel pressure regulator, but the problem is that they can be mounted only on return fuel systems, throwing a serious monkey wrench into my plans. I was wondering if there is any way to convert our stock returnless system to a return system capable of taking a fuel pressure reglator? I think daewooluvr may have done this mod because I remember seeing some extra fittings on his fuel rail and hearing talk of it being a return system.

How complicated would it be to do this, also, is it worth it, or should I just run the nitrous alone, no fuel regulation (it'll be a small shot only). I have some pretty good machining skills and access to some tools, but I'd like to know if anyone has done this and how it is to be done.

Thanks guys for all the help!

MMamdouh · Post by **MMamdouh** » Mon Feb 12, 2007 11:47 pm

first off i think we got return system on our woos... pop the hood and go to your fuel rail you will see the feed going from the left side and the FPR and return line on the right so this is a return system (unless i got something figured out seriously wrong)

we did install a RRFPR on the turbo 2.0 nubira and the fitting was a peice of cake and the nubira had a return fuel system a well so i recon you don't have to do any modding on your current fuel supply setup to accomodate the RRFPR.

MMamdouh

exist3nce · Post by **exist3nce** » Mon Feb 12, 2007 11:56 pm

If it is returnless (my 2004 Optra is), I know it is possible to convert it to return fuel system. I know the general idea/concept of how to do it, but not the specifics lol.

MMamdouh · Post by **MMamdouh** » Tue Feb 13, 2007 12:00 am

i know that the newer models like optras and all got returnless fuel system and i am sure the older lanos/nubira/leganza has return system.

MMamdouh

ubuyau · Post by **ubuyau** » Tue Feb 13, 2007 2:19 am

MMamdouh wrote:i am sure the older lanos/nubira/leganza has return system.

+1. They do for sure.

--Tim

Post by **PrecisionBoost** » Tue Feb 13, 2007 2:46 am

Yes.... the Nubira, Lanos, Leganza all came with a return fuel system..... but the Optra/Reno/Forenza/ has a returnless system.

Typically I belive that the stock regulator is built right into the fuel rail on the Leganza/Nubira.... not sure about the Lanos.

I am also looking at the current system.... once I figure out how the stock system sets fuel pressure on the returnless system I will let everyone know.

gse_turbo · Post by **gse_turbo** » Tue Feb 13, 2007 2:55 am

see, regulator and inlet on the left, outlet on the right.

garrett

Post by **PrecisionBoost** » Tue Feb 13, 2007 5:19 am

Ok..... I went through all my manuals and the Optra/Forenza/Reno/Lacetti as well as Aveo/Kalos use a returnless system where the fuel pressure regulator is inside the fuel tank.

Basicly it's the same as the one you would find on the Nubira except it's inside the fuel tank instead of on the fuel rail.

It's basicly a diaphram held in place via a spring.... as fuel pressure rises it pushes down on the spring allows fuel to bypass the diaphram.

With a return system the fuel goes into the "return line" and makes it way down a line all the way back to the fuel tank.

In a returnless system the fuel simply falls back into the tank.

So..... with a returnless system there is two options.

1) Remove the fuel sender unit and increase the strength of the spring.... which will increase fuel pressure
2) add an inline system to boost fuel pressure outside of the fuel tank

The problem with #1 is that it's a one shot deal..... it raises the fuel pressure all the time.... so it will run rich at idle, partial throttle and wide open throttle

So.... for a returnless system the best way to go is to add an inline booster system.

It looks like this....

Basicly the fuel control module senses the vacuum/boost and turns on an inline pump to increase fuel pressure.

So at idle and everywhere else the inline pump is shut off.... and regular fuel pressure exists throughout the system... it simply flows through the check valve unchanged.

Then as boost kicks in the controller turns on the inline pump.... which sucks fuel in from the fuel tank and then pressurizes it according to the controller software. ( ideally a digital controller)

The fuel stops flowing through the check valve and only goes through the inline pump since the pressure on the right hand side of the check valve will be higher than on the left.

The cool thing is that it can be used to give you very flexible management of the fuel pressure and thus injector output.

Now..... you might say " sounds great.... where can I get one" and my answer is " I don't know.... I haven't got that far on my research "

Oddly enough.... I can't seem to find anyone making this yet.... but I've found the diagram for the solution on several different sites.... including one on supercharged mustangs.

Anyways..... now that you guys can see what the system consists of..... perhaps someone will stumble accross a company building these systems for a returnless system.

Oh..... I added a few things in like the fuel pressure sensor... it seems that they use one.... but it doesn't normally show it on the diagram.... so I added it in there... since it's absolutely necissary.

Post by **PrecisionBoost** » Tue Feb 13, 2007 5:23 am

Well a Walbro inline pump costs about $120..... so I don't imagine this is a cheap solution.

Summitracing has an inline MSD pump for $94.98

Post by **PrecisionBoost** » Tue Feb 13, 2007 5:48 am

Here is a good link showing a problem a guy had.... http://home.alltel.net/mcfly/returnless.htm and it has a link to a digital Fuel management unit (FMU )... but the link is broken.

Ok.... searched Yahoo for returnless digital FMU and whamo.... a pile of hits.

Ouch $419 for one of these units.... http://www.wildponymotorsports.com/prod ... roduct=656

Nothing found on Ebay.... and it seems that Aeromotive Inc. company is one of the very few companies making these.

So that means your looking at something in the range of $540 to get a fuel management system for the Returnless system.

Hmmm..... well.... at that level of money it's probably cheaper to simply install a Piggyback Engine management system.

The Perfect Power SMT-7 is a nice unit.... and the SMT6 isn't bad either.... pretty good bang for your buck..... probalby less than $400

Audacity Racing · Post by **Audacity Racing** » Tue Feb 13, 2007 5:49 am

You could modify the stock system to have a return for that kind of cash...

MMamdouh · Post by **MMamdouh** » Tue Feb 13, 2007 4:21 pm

chris@PrecisionBoost wrote: Typically I belive that the stock regulator is built right into the fuel rail on the Leganza/Nubira.... not sure about the Lanos.

well... talking from engines point of view, the 1.4 SOHC, 1.5 SOHC, 1.6 DOHC got a FPR that can be totally removed from the fuel rail, the 2.0 DOHC and 2.2 DOHC got a FPR that is partially integrated into the rail and you can only remove the top part of it.

MMamdouh

BosnianLanos · Post by **BosnianLanos** » Tue Feb 13, 2007 10:44 pm

Ok, so the Lanos did come with a Return system?

I'm sorta confused.

The new models of the GMDAT line are returnless, but the old ones are return, but they have almost the same engines. LoL, beside the point.

Would this mean that I can install an in-line fuel pressure regulator, like the ones you get off *GASP* Ebay?!

I wouldn't install such a cheap version because a friend with a built eclipse has had a few go bad on him, but would something like that work, and how would it hook up, considering that the fuel lines of the Lanos are hard plastic with special ends.

Also, this Perfect Power SMT7 sounds like a really good investment (I have some money to $pare). Is it just a matter of just hooking it up the the ECU and tuning it via Laptop, or is it more complicated than that?

Thanks for the help guys.

davids06aveo · Post by **davids06aveo** » Wed Feb 14, 2007 12:00 am

I have an Aveo that I am trying to turbo right now with the same problem
of a returnless fuel line. It was mentioned that you could modify the stock
fuel rail instead of spending the money to make your own or buy a
piggyback to tune it. Any suggestions on how to modify the stock fuel rail?

Post by **PrecisionBoost** » Wed Feb 14, 2007 12:54 am

BosnianLanos....Yes.... Lanos is a return system... and MMamdouh confirmed that it can be removed so you can buy an adjustable regulator off ebay or where ever and you shouldn't have a problem

David / Audacity ..... the returnless system was designed to reduce evaporative emissions.... it's possible that the Aveo might not allow for a simply change over to a returnless system.... it may cause it to fail emissions testing.

I do agree you could make it into a return system for that kind of money... but then you have to add an adjustable fuel regulator ( or rising rate ) and then fine tune it with something such as a SAFC.

Going direct to a piggyback would be easiest and cheapest for a low boost "returnless" application given all the options.

there are many different management systems.... some are easier to tune than others.... so allways do your research and get opinions from people that own them.

Tom (GSiTurbo) went with the Greddy e-manage system because it interfaces with his Profec E0-1 Electronic Boost controller.

Kinkyllama has the SMT6 ( or is it SMT7 ?? ) but I don't think the turbo is up and running yet.

Tom and I know someone with Renualt turbo using a Megasquirt (Tom did most of the install and initial setup of the unit ) so he could comment on that unit as well.