How to: Le5 fuel return system. - Page 2 - Saturn Sky Forums: Saturn Sky Forum
Saturn Sky Performance Discussion Internal Engine | External Engine | Suspension | Exhaust | Upgrades and Aftermarket

User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #16 of 28 (permalink) Old 02-16-2016, 02:43 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
True, I just can't trust just anyone to weld up fuel systems though...don't know if I have a shop locally I can trust for that.


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #17 of 28 (permalink) Old 02-16-2016, 02:44 PM Thread Starter
Senior Member
 
Join Date: Mar 2010
Location: La Crosse,WI
Posts: 176
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
You may have to find something that works then or get one custom made.
slvrsky07 is offline  
post #18 of 28 (permalink) Old 02-16-2016, 04:27 PM
Senior Member
 
Join Date: Apr 2015
Location: Lake Orion, MI
Posts: 268
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
You don't need to weld to have a return system.

Do almost exactly what he did, but instead of welding the fitting on, just run a regulator "inline" with the fuel rail.




The OP did the top version, but the bottom version works just as well. It's easiest to intercept the 3/8 fuel line underneath the car before it turns into nylon braided flex hose. You will want to use Swagelok SS-600-6-6AN fittings (no special tools needed) or a 37* flaring tool and -6 tube nuts. This will let you run the hard line to braided hose, braided hose to the regulator, regulator to braided hose again, and the braided hose to the fuel rail. The fuel rail can be adapter by using a 3/8 to -6 GM rail adapter. You'll want to pick one of the manufacturers that make the locking adapters such as the aeroquip ones:



I also think the OP would have been much better off using the stock filter that sits inside of the tank, it's actually fairly big.

This can all be done with the tools in your garage, except for maybe that ridiculous hard to get off fuel tank ring (OTC 6599 ~$40)

Last edited by LT1Pat; 02-16-2016 at 04:31 PM.
LT1Pat is offline  
post #19 of 28 (permalink) Old 02-16-2016, 05:06 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
Hmmmm...

Correct me if I'm wrong LT1 (and I suppose I am) but I always thought the benefit of a return system was that all the injectors in the rail got the same fuel pressure because the fuel is allowed to travel through the whole rail before returning the excess pressure "Bleed off" to the tank?


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #20 of 28 (permalink) Old 02-16-2016, 07:53 PM
Senior Member
 
Join Date: Apr 2015
Location: Lake Orion, MI
Posts: 268
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
You supposed right! You can think of the stock system as a return system, except it returns inches from the fuel pump with a ball and spring. The return never technically leaves the tank so it's always metered right at the pump.

Now for some math:

fluids are subject to p=r*g*h : r is rho (density), g is acceleration (usually gravity) and h is the difference in height. When we're talking about a return style system, there isn't a pressure difference between the regulated pressure in the tank and the fuel rail because there isn't a difference in height. This is looking at the car from top to bottom.

Now here's why it matters. When a car accelerates or brakes, it's producing positive and negative acceleration forces or (g's), usually in the magnitude of 0-1 for a normal car. Now the "h" in that equation starts to matter because the acceleration forces are lateral now. This means that if there is a length difference of 12 feet from the tank (the spot at which it's regulated) and the fuel rail (the point at which pressure matters) then we're looking at a pressure difference.

Gasoline @ 60* has a rho of 711kg/m^3
Assume .5G positive acceleration .5(9.81/2 m/s^2)
Assume a distance of 12 feet from the gas tank regulator to the fuel rail (3.6 meters)

deltaP=711kg/m^3 * 1/2(9.81 m/s^2) * 3.6 meters
deltaP=25.08408kPa or 3.63 psi.

This means that if the stock regulator is set for 410kPa (59.46 psi) then the front of the car will only see 55.83 psi when you're accelerating at 4.9m/s^2. The exact opposite would happen when you're braking (higher pressure in the rail than the regulator).

By moving the regulator to the same "h" as the fuel rail (or next to the fuel rails) then you can always have a consistent pressure. The fuel rails should have the same pressure just before the the fuel enters the fuel rails, and throughout the fuel rail itself (unless the fuel line or fuel rail is a restriction). 700+hp can be made on -6 hose so I don't think the typical LNF guys are anywhere near this restriction.

Quote:
Originally Posted by Robotech View Post
Hmmmm...

Correct me if I'm wrong LT1 (and I suppose I am) but I always thought the benefit of a return system was that all the injectors in the rail got the same fuel pressure because the fuel is allowed to travel through the whole rail before returning the excess pressure "Bleed off" to the tank?

Last edited by LT1Pat; 02-16-2016 at 07:57 PM.
LT1Pat is offline  
post #21 of 28 (permalink) Old 02-16-2016, 08:06 PM
Senior Member
 
Join Date: Apr 2015
Location: Lake Orion, MI
Posts: 268
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
I should also add that some regulators are "boost reference", meaning that they adjust the fuel pressure for boost and vacuum. When you have a set of low pressure injectors in the intake manifold, the air around the bottom of the injector is almost always a different pressure than the fluid in the fuel rail (as well as atmospheric pressure). Fluid always moves from a high pressure to a low pressure, and you want to keep the difference in pressure somewhat constant. If you ran 59 psi of boost, and 59 psi of fuel pressure, then fluid would only "drip" out of the injector due to gravity like someone poked a hole in a bag. This is why some people switch to boost referenced regulator, because it's the difference in pressure that moves the fluid.

A lot of this doesn't apply to direct injection because all you really need to do is deliver the fuel to the front of the car as a feed for the high pressure pump.
LT1Pat is offline  
post #22 of 28 (permalink) Old 02-16-2016, 08:37 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
Got to remember LT1, I'm on a LE5...we're port injected not direct injected so all this probably applies to me.


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #23 of 28 (permalink) Old 02-16-2016, 09:05 PM Thread Starter
Senior Member
 
Join Date: Mar 2010
Location: La Crosse,WI
Posts: 176
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
His system makes sense. I ran this setup to make it adjustable and keep the same pressure and flow to each injector. It works great for this engine. I do think his setup would work for you if you didn't want to change the rail. There's a lot of cars that are both ways we have listed here. You can always try his and if it doesn't work the way you wanted, you can get a rail or something.
slvrsky07 is offline  
post #24 of 28 (permalink) Old 09-09-2016, 02:20 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
So to come back to this since it looks like something I'm going to do, the DDM fuel rail makes this a lot easier. The rail has plugs at each end so you could (in theory) easily adapt it into a return fuel system. Now I just need to figure out what I need to do so.


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #25 of 28 (permalink) Old 09-19-2016, 05:59 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
Just adding

I'm not going to provide part numbers or anything like that for this as this is basically the same build as slvrsky did just with a DDM fuel rail and a different placement of the regulator.

I don't know which layout I'll be going with yet and won't know until the day of the install. The difference in my setup over slvrsky's is no welding is required. You replace the stock fuel rail with the DDM piece and it has ports at each end that allow you to easily convert it to a return system. Remove the plugs from those ports, put one of them in the center feed port, and it's ready to go. You can also leave the center feed in place and tie both end ports together for your return to the fuel pressure regulator but I like the through and through method better because I think it's cleaner.

My plan is to connect to the stock fuel line from the tank in the engine bay to the front of the rail. The Regulator will mount using AN fittings directly to the fuel rail in the back. Here I will have a pressure gage and put the regulator on it's side to clear the cowl at the base of the window. To still be able to access the pressure adjustment, the pressure adjustment screw needs to face the drivers side of the car. This puts the return port on the opposite side of the rail from where the line will route to return to the tank so I use a couple of 90 degree elbows to get the return facing the right direction then use the same style quick connect to connect the return line to the regulator. At the tank, a bulkhead fitting and 90 degree hose fitting will connect the braided line to the tank.

My primary layout:



My (infamous) "Plan B" layout:



And, because this is my first time designing something using AN fittings and I don't know what can go into where...my Plan B's Plan B:



The difference between the two layouts is the extra male to male and female to female fitting between the pressure gauge and the regulator. This connection runs almost DIRECTLY above the oil filter. I want to be able to change my oil filter without removing my fuel rail so if the gauge fitting alone doesn't push the regulator far enough back to have a socket and extension pass down to the oil filter housing, I'll extend it with the male to male and female to female fittings.

For those wondering, yes the regulator does have a port for a fuel pressure gauge but where I'm going to mount it would cause the gauge to face downward and make it completely useless. Thus I use this setup and it spaces the reg away from the rail like I need it as well as letting me see the pressure.

EDIT. Just wanted to add to this post for anyone that runs across it in the future. All the above designs did not work due to clearance issues with the return line fittings. Here is the final layout I recommend. Note that on the fuel inlet side of the rail I used the design above with the 90 degree hose end and a 90 degree male to female fitting because I already had them. In retrospect, I would have replaced those with a 180 degree hose end as shown in the diagram below.

Attached Thumbnails
Click image for larger version

Name:	rail.jpg
Views:	243
Size:	65.3 KB
ID:	84906   Click image for larger version

Name:	rail2.jpg
Views:	363
Size:	67.7 KB
ID:	84914   Click image for larger version

Name:	rail3.jpg
Views:	239
Size:	67.2 KB
ID:	84922   Click image for larger version

Name:	rail3a.jpg
Views:	209
Size:	110.7 KB
ID:	87345  


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.

Last edited by Robotech; 12-04-2016 at 04:28 AM.
Robotech is offline  
post #26 of 28 (permalink) Old 09-19-2016, 06:25 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
Quote:
Originally Posted by LT1Pat View Post
I also think the OP would have been much better off using the stock filter that sits inside of the tank, it's actually fairly big.
I just noticed this and after taking apart my fuel pump assembly to do what the OP did, my question is how would you use the stock in tank filter without using the stock in tank regulator? They look like (from what I can see) tied into one another.

The line from the pump goes out and into a fitting that, I assume, directs it into the filter and the regulator. Then another line comes out of the assembly and heads for the lid to go out to the engine.


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #27 of 28 (permalink) Old 09-22-2016, 05:05 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
Just got the last parts of this ordered today. Have a lot of it assembled already. Will take some good pics once I start installing to show my version of this build using DDM's rail. Should be a very easy build that anyone who can change the injectors should be able to accomplish.


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.
Robotech is offline  
post #28 of 28 (permalink) Old 12-03-2016, 06:29 PM
Super Moderator
 
Robotech's Avatar
 
Join Date: May 2006
Location: Temecula, CA
Posts: 10,412
Mentioned: 58 Post(s)
Tagged: 3 Thread(s)
Quoted: 1606 Post(s)
Garage
This was a huge help in my return system.

I did a write-up on this on my version using the DDM fuel rail and a FueLabs regulator. Want to make sure the author of this thread gets credit too since mine is just a tweak to his original idea.

https://www.skyroadster.com/forums/f2...5/#post1137033


V.A.L. (#1108)
2007 2.4 Base
MagnaFlow dual outlet, quad tip exhaust test car
**Sold**

Max (#1547)
2007 TURBO 2.4
Too much to list here. See my Garage for details.

Last edited by Robotech; 12-04-2016 at 04:32 AM.
Robotech is offline  
Reply

  Saturn Sky Forums: Saturn Sky Forum > Saturn Sky Discussion > Saturn Sky Performance Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Saturn Sky Forums: Saturn Sky Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome