My plan is to run a LS2 in an Ultima GTR but I just read in popularhotrodding that the ls2 is "Returnless, sequential port fuel injection". Does this now mean that I now longer have to plan for a return line back to the tanks?
thanks.
chris

 

You always need some sort of return from the regulator back to the tank. With the later F-bodies the regulator was in the tank and a single line runs to the fuel rail. With the later Corvettes the regulator is external, but mounted near the tanks. A single fuel line runs from the regulator down the length of the car to the fuel rail and a short line back to one of the tanks.

The LS2 uses a single feed fuel rail just like the later LS1.

SO... If you use an external regulator, you will need a return line. If you run an internal pump/regulator combo then you don't. Most LS1/2 swaps have been using the external 99+ Corvette regulator mounted near the tank.

 

Thanks 70, I will stay with my origional plan then and use a return line. I have attached a pic of the system I plan to use (its a copy of one on the net)
chris

 

this is just something small i wanted to point out to you..

since you have only one fuel rail inlet, you need to slightly modify that setup.

first off. everythign between the pump and the regulator, is at the regulated pressure.
this means that you can do exactly what the factory does, and tap off that line anywhere to get your fuel rail fuel. you can see that in my attached pic.. everything thats highlighted yellow has the full pressure.

the way i layed it out here, the fuel goes to the regulator and back out to the rails.
this is very similar to how most of the 3rdgen and other factory fuel injection guys convert theirs.. your only diff is the surge tank for high G fueling...

 

How much power are you going to be making? And why the surge tank?

 

Power should be in the 450/500 range to start with. Most of the guys that have done this (only a few) on an Ultima are running a surge tank to ensure that the high pressure pump does not starve for fuel. Ultima suggest that you run a SBC not LSx motor so it’s experimental for me. The few others say that the above set up works, not necessary the best but works so I thought I would ask opinions.

Thanks to both of you for the suggestions / help!

Dude - I see your point, in my drawing I don't think I had it regulating properly.

 

what you have there is basicly what the sand rails run... lots of off road cars run something like that.

personally, i think its WAAAY overkill, but ive never made a car that had dual fuel tanks.

what is the stock reccomended EFI fuel system like?
i would just do that, but attach the rail to the regulator.

 

Not sure on the stock set up. The motor is coming out of a '05 Vette. As far as duel tanks its new to me also. I have never played with FI before so this is a learning experience for me. After the motor goes in and is running I plan to do some mods and learn about tuning. I would think with the very short exaust and no cats it will need some tuning at the start. I think its time I stepped away from those old school carbs and move into FI.
chris

 

Hijacking in progress....
MrDude... I remember you telling me a while back that i needed a low-pressure pump like the one you drew in that diagram, i'm wondering if its completely necessary. I don't want to run one. Won't it work just like this?....



olly

 

My setup is exactly like your picture with the inline pump to the vette FPR to the fuel rail. I have had no starvation issues at all. I didn't even sump the tank. Just used the stock 1970 fuel outlet pipe.

 

thanks, jeff. wish someone coulda told me that when i posted about it 3 months ago. oh well. Now i've got a basically starvation-proof sump setup.
sweet.
olly

 

you probably have me confused with someone else..
the only time ive ever even seen that kind of setup is on offroad cars.

im a big fan of something SIMILAR to what you posted... the only diff is i HATE external pumps.. they're loud, and most have a high failure rate compared with the quiet, reliable intank pumps..

but yea, that works, thats whats in my car, except my pump is in tank.


the only reason i left his pic like it was, was because i dont know about that part of it.. but he was asking how the high pressure side hooked up..
ive never even seen ultima GTR fuel tanks, so i didnt know if the rest was needed or there or what.. so i just showed how to attach the "returnless" rails.

 

That's a great diagram. May I ask what site you got that from? It looks like the long lost site I had before my computer crashed! Thanks in advance. Gar

 

Its here:
http://www.markkoch.net/

I have been following his build for some time now. I love the turbo set up and hope to follow his design after my car is running. His is the Can Am version not a GTR (roadster vs coupe). Several others have posted the same basic fuel design on Pistonheads.com all with similar concerns. With dual fuel tanks do you pull fuel from one and return to it or the other or as Mark has done to a swirl pot with overflow. And where should the overflow go to. should the tanks be connected? if they are how big a line and then how do you fill them up? If you fill one it will be draining into the other at a slow rate but it will still drain. Do they make a check valve for a line 3/4"? As you can see going against what the factory recommends adds complexity but I love a good challenge.
Thanks - I like the last design.
Chris

 

Hi there Chris.....

Speak to Jeff Schwartz.... he has a single pump setup on his and did the same for mine. I also had larger (-12) fittings put into the tank so that its easier to fill from one side....if you search PH you will find posts from him about his setup.... or email him - he's very helpful

GC

 

Thanks crafty I will. I am headed down to Flordia at the end of the month to check out a few other Ultima cars there and maybe get a few ideas on different set ups. Has Jeff shipped your motor etc. ? I know you can't wait!!
chris

 

take lots of under "hood" pics and post them!
thoes guys always have something cool under there....

 

Engine should be leaving Jeff's today... should be in UK next week and then packed with the chassis and sent here...... it was ready before Xmas but I decided not to send it as it would have been sitting in a UK port over Xmas....

so... I should get the whole lot mid Feb... You are right - the suspense is killing me - had to ease the pain with some tool shopping over Xmas.

 

like this?