If you complete this reading material.... you will understand perfectly why you SHOULD NOT plug up your stock fuel pressure regulator when installing a return system!!!

Lots of you probably know who I am because I have been a frequent on this forum for a while now. I do what I can to help and offer advice when possible. I used to get a lot of PM's from people asking me who does all the world on my car, etc... for many, it was not exactly clear that I was the owner of a performance shop that has taken in the 350z as a project and R&D vehicle.

Well, I am proud to now be a sponsor of this forum. I wanted to let people know that we are going to be continually testing and developing product for the 350z. Our product will always be a product of R&D and personal hands on experience working with the 350z inside and out.

Anyhow, enough of that stuff

We have been testing and developing a fuel system for the 350z. When it is finally complete, well, it will speak for itself. Give me some time to finish and test the rest of it.

Right now I am "going public" with one component of the fuel system. This part of the kit is available seperatly, and right now. I am going to explain here how return fuel systems in the 350z should work when properly engineered.

Lets starts start out with a little bit of explanation... Most of you have seen this white plastic fuel pump assembly in your Z... but what is inside of it... what exactly is it doing that you cannot see?

Take a moment to read this diagram I made.



How did I figure this all out? Easy... I used the band saw and sliced the pump assembly horizontaly into 4 parts.

So what is most important to notice here is that the fuel that is relieved by the fuel pressure regulator is sent to TWO jets. One of them uses the flow to pull in fuel from the drivers side of the gas tank and then put it inside the catch can... and the other one shoots the fuel back into the catch can to help pull in more fuel from outside the can and also create a swirl pot effect to keep the catch can's reserve of fuel as high as possible.

Simple enough to understand now.

So lets look at how we bypass this internal regulator system and add our external regulator to get the 1:1 rising rate.

Almost everyone has been plugging the stock fuel pressure regulator completely. Then they run a return hose thru the top of the pump assembly back into the can.

This works... but... there are 2 problems with doing it this way.

Problem 1: It is a physical IMPOSSIBILITY for any fuel to be pulled from the drivers side of the tank now. Your pump will run dry at roughly 1/4 fuel gauge indicator level. If you are WOT, this could blow your motor... and you would be left wondering... what happened?

Problem 2: The lower swirl pot jet is now disabled also. This means that there is no swirl function in the can. This means the cans fuel level will be no higher than the level of gas in the tank. This is because there is no swirl function to keep gas inside the can. With the swirl properly operating the can will actually be FULL to the TOP even if there is only 1" level of gas. But without the swirl, gravity will cause the fuel in the can to level with the tank thru the hole in the bottom.

So... now we know that we cannot simply PLUG the spot where the stock regulator goes.

The fix is easy really. What has to be done, is you need to somehow get your return fuel to power those jets again.





Thats right... this is not a solid plug. What this item does is plug ONLY the T where the fuel feed channel feeds the stock regulator. However it is open in the bottom to allow you to return your fuel back thru this fitting and once again power your jets.





So you can see, the bulkhead fitting that goes thru the top of the pump assembly now has a barbed nipple on it... and a hose that runs into another barbed fitting that threads into the bottom of this plug. We now have our return fuel going exactly where it was meant to go from the factory.

Most people do not know this... but the APS kit addresses this exactly the same way. I am offering this product without having to buy the APS kit... and this uses AN fittings rather then having hose simply clamped on a pipe external of the tank.

NOW... we are going to take this one step further.

Think about what is happening in the system. Your car is at idle... it is BARELY burning any fuel at all. But your pump is going full blast just pushing all this fuel. This means that your return line is very busy evacuating all this fuel to keep pressure where you have it set.

The problem here now is that ALLL this fuel has to be pushed thru those 2 small jets!!! Those jets are PIN HOLES!!

We found that with factory jetting the walbro 255 pump, fuel pressure could not get below 55 psi... and this was with the pump at only 12v.

So what is the solution? You dont want to modify the siphon jet, because then you would be pulling in fuel very fast from the other side, and you would run that side of the tank dry quickly. Not to mention, you will never get to the siphon jet before you destroy the pump assembly.

What you CAN get to is the swirl jet. This jet can be removed (VERY CAREFULLY).

Get a drill bit that is 0.0750" in diameter. and DO NOT put it in a drill, but use a hand tool to run it thru the swirl jet.

Now, you will find that your min fuel pressure is going to be around 35 psi.


Here it is in action. Notice how the can is overfilling because of the swirl effect.. very nice. NOTE: The gas in the picture appears frothy... this is because I left the siphon inlet OPEN and it is sucking in air... this is why it is so bubbly. If we placed our finger over that siphon inlet the fuel calmed down.

PERFECT... Everything is now simply perfect. Now everyone can and will do it... with or without my product

http://www.cj-motorsports.com/produc...turnsiphon.htm

So I present this product. It can be used by someone who is making their own fuel system... or it can be used by someone who wants to correct a different fuel system... or it will be included with the rest of the CJM fuel system due out in a few weeks.

-Charles
CJ Motorsports

 

Really nice R&D Charles. Thanks for sharing this with us. And welcome as a board sponsor. You have been an invaluable resource to ALL of us on the board!

 

First, congratulation on becoming a sponsor on this board and thank you for sharing your findings and R&D with all, including your competitors, this really shows they type of person (company) that you are

Thank you for being you,

Az

 

Good work charles can't wait to get ur setup in my car

 

Good work charles can't wait to get ur setup in my car

 

Looking forward to it Charles!

 

Real nice explanation. Looking foward to buying your system, minus the parts I am already running.

 

Hello Masters
what is the main Differance ???
I mean AAM and CJ Motorsports Fuel system ????
and this kit looks like My APS fuel system not everything but some!!!!

 

Awesome work. I really appreciate all the R & D! When I do go F/I, I'll be sure to do it correctly with your system.

 

so, i know you saw this coming a mile away....

what do you think about a group buy???
I know gq_626 will be #1 on the list...I'll be #2

-TODD

 

Count me in as number 3 if there is one

 

confirmed #1.

 

if there is a group buy award of 2004...i nominate sharif as a prime candidate

 

Sorry for my interleaved and garbled post ....

Good analysis, also another Kudo to APS for being one of the few "if only" kit builder to figure this out as well ,along with the crank wire etc etc.

 

i believe that Ultimate Racing might have been doing something like this as well in their kit for quite a while now... so I am told. But this is not verified yet.

All it comes down to is anyone that wants to sell a product, such as myself, and other manufacturers... need to do the R&D on this stuff in order to provide a real world working solution to the customers. Too many manufacturers are quick to slap things together, sometimes perhaps by making small changes to a part they already make, and never even test fit or road test, etc etc.

I can understand that on some parts where real world testing would be too costly on every single engine and that it needs to be installed only by someone who knows exactly what to look out for... but with a fuel system... there is not much you need to look at.

Dealer cost on a fuel pump assembly was a mere 240$ for me... so i really had no excuse not to just buy one and cut it up. With me sharing my findings, those of you who learned from my findings are able to make sure whatever you do with your fuel system is going to function properly, with or without my product. I know I am not the first to do this, I am just the first to explain why its done and make this available without buying a full turbo system... it really was made just as a part of my premium fuel system to come out soon, but i figured since so many people are running plugs in their assembly, that I might as well sell it seperate to correct their problems... or at least show them how to correct it by themselves.

I also felt it was worth mentioning the proper way to modify the pump housing to support all that flow of the walbro 255 pump... simply putting in that pump can create excessively high fuel pressure, depending on what your pressure goal is. Drilling the swirl jet corrects this problem.

-Charles

 

Confirmed #4

 

Thanks for all the kinds words, everyone.

As for the group buy... that might be an option. Let us finish up some stuff and when I make the announcement on that product, we can possibly give it a shot. I am not sure there is a huge market for the fuel systems right at the moment since I think everyone already bought stuff for their winter engine build project... but we will see. If there is good demand for a group buy, I dont see why not. Give me some short time to show you guys the details on what you get for the money as soon as its ready to be displayed.

 

nice findings and write up.

 

Thanks G3po, it's nice to see some recognition for APS's effort to engineer and design a fuel and ignition system that's up to the task for the 350Z with FI.

Peter

 

Yes they do, and it works, however, the setup is a bit different then yours.

Az