So heres my setup. Details on drivetrain must be kept private but Ive been able to get this to work perfectly thanks to Larry at SP who ive been talking to for about 3 months now(who might I add has done a great job at helping and putting up with my phone calls) I wanted to run an external pump setup to supply my engine with enough fuel. I was able to do it without using those swirl cans or whatever you call them.


Heres the top of the bucket. I had Larry weld a pipe to a -10 stainless fitting that would be used as the feed for the pump. The other one is just a -6 return used from my previous setup.


Heres the pipe and you can see how much CAREFUL cutting is required in order to keep the two posts and get the pipe and nut to fit in there


And here is sort of a mock up how it works. Basically it draws fuel from the pipe into the pump to the rails to the FRP back to the tank via the -6..and from there it goes into one port of the venturi and as the fuel is forced into port one and out port 2 it creates a vacuum to port 3 which sucks fuel from the other side of the tank.


You have to hook port 1 up to the return line port 2 just dumps back into the passenger side anywhere and port 3 on the venturi as to be brought over the other side of the tank(try to get the tank as empty as possible)


For anyone trying this I pray you have patience because you are going to need A LOT of it. I pushed my venturi unit off to the left side of the bucket so that it wouldn't interfere with level sender or get stuck under the bucket. Once you get all the right lengths everything hooks up and my pump is pretty far from the tank(right under my driver seat) and it primes pretty quickly and supplies constant pressure perfectly. You have to cut a few big holes in the bottom of the bucket to make sure the pump doesnt suck it dry before it gets to fill it back up.

 

that will be nice for that big turbo on that V8!

 

I spy an LS valve cover in that picture. LS's have those really short (ugly) valve covers. It looks like an LS..........should be a fun project.

 

Nope.....

 

What size is the external fuel pump you are using? Do you have a voltage controller to reduce voltage at lower engine load?

 

Magnafuels dont require a voltage step down. I have the 4301 flows enough for 1500hp.

 

So, just so i can be clear... you plan on running a 1500hp fuel pump. with a return fuel line through a -4 bulkhead fitting, and then a pinhole sized venturi?

You might want to reconfigure this a little, unless you are going to idle at 6000rpm Your idle/low rpm fuel pressure is going to be off the charts... the return is too restrictive for the regulator to do its job.

 

-4? Im running a -10 bulkhead to the pump -8 to the rails to the aeromotive 13101(the bigger one) and a -6 back. I had the system runnnig today at 76psi(stock is 58 but I wanted to check for leaks) for an hour and 20 min and the pump barely got warm. The venturi was working EXTREMELY well(much better than I though) I had the driver side spot open and the hose had quite a bit of vacuum on it. It was keeping the driver side full and was spilling back over.(how the stock one works)

 

Oh and I was able to get pressure down to a stable 40psi(regulator says 35psi but 40 was as low as it would go). Which is lower than the car will ever see. Not to mention this was with the engine off so it might go a little lower once the injectors are working.So however small the hole was it seemed to be working pretty well. Have you ever looked at the return port opening on a FRP? The 13109 is tiny and the 13101 isnt much bigger and is rated at 1000hp.

 

Nice

 

The -4 I was referring to is the bulkhead fitting for the return line. In your pictures, its a -4 bulkhead, with a 4/6 adapter on it. The hose is 1/4" it looks to be.

I have had issues on the test bench with return setups that small with much less than a 1500hp pump. I am surprised that you are able to get down to 40psi, unless that pump isnt really that big. Your pressure may still go up once the voltage is higher with the engine running and alternator turning.

Regulator outlets are pretty small, but its a very short restriction. The duration of a restriction matters just as much as the size of it. I used to try running complete -4 return lines on 350z's with a single walbro... couldnt get pressure in check at idle. Replacing the line with a -6, but still using the -4 bulkhead and 1/4" inside the pump assembly fixed that. If we only needed the return line to match the size of the regulator outlet, we could use -3 returns!

For comparisons sake, a stock 350z pump assembly has 2 venturis off the return line, and even then with a single walbro you have to drill one of them out larger to get pressure in check at idle. Now imagining your car, you have whats supposed to be a 1500hp fuel pump. When pressure testing it with the engine off, that pump might as well be running into a dead end with nothing but a pinhole to vent pressure. If the pump is really 1500HP large, how could it possibly only be generating 40psi? A single walbro will generate more pressure than that, and anyone who tried to use a Walbro without drilling out one of the 2 siphons can attest to that.

More comparison; the APS twin walbro assembly uses a single venturi on the return like that, and it has caused plenty of headaches. When they first released the pump, the venturi opening was too large for the venturi to operate during any return fuel volumes less then engine idle, and causing fuel starvation after 1/2 tank. So then they started shipping a press-in part for the venturi to restrict it more so that the siphon worked during driving too... but now it was too restrictive to idle without too high of pressure.

In our twin assembly, we got rid of a return venturi all-together because we found that, after several different test sizes, when using 2 walbros, it was either too restrictive to control pressure at idle, or too open to create a venturi effect when at cruising RPM... Same problems the APS had. The only solution was to stage the pumps, but we couldnt expect the customers to all have setups capable of staging fuel pumps.

A last comparison... I believe that SPs triple pump setup in Toms G35 is running staged pumps. I would ask Larry if thats true or not, because I cannot remember now. But if so, was that because the venturi was too restrictive with two pumps at idle? Or was that at least one of the reasons?

Ive been wrong before... so if when you have this car running and driving, if you experience no issues with fuel pressure at idle, and no issues with the car starving of fuel just below a half tank, while flowing over 600hp, then definitely let me know... but as it stands for now, i foresee issues ahead, and I am questioning the output of the fuel pump.

However, I like to see ingenuity and custom work, so props on going your own route. I am not trying to knock you... just very confused at how this all adds up, and trying to help. You have probably noticed by now, that I think about fuel systems a lot... so I am just trying to figure this one out since it is going against previous experiences.

 

Im glad that you got it all sorted out!!


Charlie, this is basically the same setup we run on our Z and quite a few Z's now as well as supras (although they dont have the venturi siphon obviously). One big pump with a -10 supply and - 6 return. I can get the fuel pressure down to 35 psi in our Z although I had to drill out the return hole in the regulator as we always do when running one large external pump.

 

well alrighty then!

 

I understand where you're coming from exactly however like I said so far its been good. And I tested it with the car off but I had my other car running with jumper cables going to my Z's battery to simulate a running car.You'd think the fuel systems pressure would be the highest with the injectors off correct? There is absolutely no fuel going into the engine only to the FRP and back to the tank. I understand where you are coming from with it being too small but the venturi isn't much bigger than the -4 bulkhead so making that bigger wouldn't make much of a difference and as Larry stated he runs this same type of setup on his car and I think he mentioned he had an even bigger weldon pump on his car.

With the top bolt on the FPR all the way loose I was seeing EXACTLY 40psi constant(and this was on a 1000$ digital snap on fuel gauge). I let it run that way for a while(I had the system running for a total of about 2 hours)..then I turned it up to the factory 58psi for a little while then I turned it all the way up to make sure if I had any leaks they would show themselves. The pump is a magnafuel 4301 and supports 1500NA hp as stated on their website.

 

It sounds like you have pretty much simulated actual use, and you're right, with the injectors firing, your lowest pressure will be even lower. I guess there is something I am over-looking... but its cool that its working. I guess its very possible that that venturi is sized differently then the 350z one internally also, Ill have to take a look at one of those.

thanks for posting

 

Once the car is up and running I will drive around for a week or so and monitor the fuel pressure very closely and post my feedback on here.

 

This is with the car jumped to my daily to simulate a running car and the screw all the way out on the fpr.

 

I'm glad you are pleased with the setup. I believe I spoke with you on the phone at SP the other day.

Reid

 

how is this big single turbo LS2 project coming along? the pics i saw on the other forum look pretty good.

 

Larry, you drill out the bottom of the Aeromotive regulator? I've never had a problem with the -4 return on our RFS. We do put a decent sized hole in the canister siphon jet though.