im doing a return fuel system on my xb and im going to document everything so i can make and sell kits. im going to try it with two diffrent fuel pressure regulators. one is going to be a 1:1 and one will be a 12:1 fpr im leaning more tward the 12:1 mostly because the xb dosnt run much boost. im not sure what the forums police is on post like this (feeler thread) but i will become a forum vendor if the price is right if i need to to advertice my products. so just chime in if your intrested in this kit or have any questions or anything to add.

 

I'm Interested! Let me know how it goes.

 

1:1...thats what I used on my setup...max fuel pressure is gonna be about 55psi with the in tank regulator in place.

 

the kit i will be sellin will inclued ethere a detailed instrution on how to block off the in tank regulator or a cap off system but it will defenitly included a way to block off the in tank reg. i no alot about the in tank static regulator systems and there very easy to bypass (normaly). this will allow you to run full pressure as high as your fuel pump will make. thats why im leaning more twared the 12:1 fmu.

 

also if someone can chime in on what the stock in tank regulater is set at it would be great because i still dont have a wideband yet (ordered it just hasnt arived) and i dont want to set my base pressure to low.

 

45psi +/- a few psi

 

44 ~ 50 psi as per the Service Data Sheet.

 

Okay, for the rest of us, what does a return fuel system do?

 

ok the xb along with a lot of other new cars are using a fuel system that’s called a static pressure system meaning it stays the same psi of fuel no mater what the vac or boost pressure is. this is not good for turbo cars. a return fuel system is where you have a fuel pressure regulator (fpr for short) the gas goes from the fuel pump to the regulator and then to the fuel rail ect and there is also a line that goes from the fpr back to the fuel tank to return fuel. the reason it needs to return the fuel is because the pump makes 100psi sometimes more and you don’t need all of it so you adjust it with the fpr now this is the part that helps the turbo guys you run a vac line to the fpr and the more boost you make the more fuel pressure that makes it to your injectors. now threes different kind of fpr and there’s also fmu (fuel management units) a fpr is on a 1:1 scale it will add 1psi of fuel for every 1psi increase in boost. a fmu is on a 12:1 scale which means it you fuel psi goes up 12psi for every 1 psi of boost. fmu are basically a cheaper way of adding fuel compared to bigger injectors. injectors are rated at a psi basically if they say its a 250cc injector its 250cc at say 55psi but if you change the psi to say 75psi it now flows more like 280cc. so in short terms a return fuel kit/fpr is a cheep easy way to mechanically adjust your air/fuel mixture.

 

Thanks for the great explanation.

Is there a similar gadget for mpg - the harder I mash down on the accelerator the better mpg I get?

 

Very Interested......please keep us updated.

 

Why not run the Boost-a-Pump from Kenne Bell? Easier to install and cheaper. Turns on at at 3lbs of boost and is adjustable from the drivers seat.
http://www.kennebell.net/accessories...boostapump.htm

 

because all that dose is increse the fuel pump speed to increse flow and psi that would not help us. basicaly in the tank befor the gas exits the tank but after it leaves the pump theres a fuel bleeder that bleeds off all fuel over 44~50 psi so even if you used the boost a pump it would still bleed of the boost.

 

So in your kit will you have a block off or a ball bearing to disable the in tank stock regulator?

 

yes the in tank factory regulator will be bypassed so you can control your fuel presure yourself with the fpr or fmu. i also found out that the factory full pump will be maxed out at around 70~80 psi so if you set your fpr to 60psi with no boost and no vac you be at 50psi at idle and 68psi running 8psi of boost. also to inform you its can ony pull 10psi away with vac so it wil go from 60psi base to 50psi at -10hg and remain at 50psi anything below -10hg. but in boost a fpr will raise 1psi for ever 1psi.

 

Sorry to jump into this thread, but the regulator should be located after the fuel rail. And you can use the 12:1 as a cheap fix as long as you are not maxing out the injectors. What i am going to do and would recommend (depending on the setup and amount of boost) is upgrade the injectors, get a 1:1 fpr, set the pressure at 45psi and I would install my fpr after the fuel rail. Also if you think about this for a second, for 1 psi of boost the fmu raises the fuel pressure 12 psi. So, on our turbo charged xb that runs 6psi of boost the fmu will raise the fuel pressure with 72 psi, correct? Then if your base setting of 45-50 psi goes up to 117-122 psi, correct? That's a lot of pressure, you are better off with getting a 1:1 fpr and if necessary get bigger injectors. They are not that diffecult to install and not that expensive. And no matter what you use, you will have to tune the setup anyways.

 

actualy the fpr i will be selling with my kit have an ajustabel ratio as well as the normal ajustabel presure you can set it at 1:1-2:1-3:1 all the way to 12:1. an it dosnt matter if its before or after the fuel rail stock it in the tank. iv been ,making custom fuel systems for cars for a long time everything from simpel return lines to full blown drag car systems.

 

Any updates on progress with this? I'm interested...

 

progress is on hold right now. waiting on fuel line as well as regulator.

 

thanks for the update. good luck...