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Fuel setup changes - Returnless to Return style on VQ35

Old 02-10-2009, 09:25 AM
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Fuel setup changes - Returnless to Return style on VQ35

I just wanted to put this info out there. When I first did my 3.5 swap I did the fuel setup the way that others had done with the Tee. It satisfied the VQ35 engine by leaving it returnless, and also satisfied the car with the return line.

Ever since running higher boost, I have been battling a little bit of a lean condition at higher rpms in the higher gears. I have tried just about everything, turning the pressure up, added a boost-a-pump, SAFC adjustments, etc. Nothing would fully fix the problem. I thought I had it narrowed down the the fpr not rising 1:1 with boost, but I fixed that and I still had the problem.

I decided to remove the damper on the end of the fuel rail and make it return style and eliminate the tee from the system. Now the fuel has to pass through the fuel rail to be returned to the tank. This seems to have fixed my problem. I can be as rich as I want now at the upper rpms. I don't know if it was a volume problem flowing through the tee, or if it was just the setup allowing fuel to be returned to the tank without ever seeing the engine. This could have been a problem if the fpr was acting up.

Here is a simple diagram showing before and after.



Click see a larger size.
http://memimage.cardomain.com/ride_i...0078_large.jpg
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Old 02-10-2009, 11:28 PM
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I was wondering....

Great info I have a similar setup to your n/a 3.5 days (minus the jwt ecu)
My car leans out up top in high gears under alot of load. I thought my problem was alternator/ vacuum or fpr related but they all checked out fine.
I will try this once it gets warm. Thanks.
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Old 02-11-2009, 07:06 AM
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fuel pressure problems as well..

96sleeper, your posting came at a great time for me! I've been battling a lean condition ( A/F 17.8 ! ) when spraying as small as a 75-shot since last November.

My FPR setup is the same as yours was - I changed out the battery, rewired the fuel pump directly to the battery, the AERO FPR, fuel rail and injectors, opened up the fuel line and wired in a manual run-the-Walbro switch and checked flow through the filter, changed out the Walbro GSS342 with a new one, and the car still runs lean when spraying. I've spent every dry and warm day out terrorizing the on-ramps with no solution.

After reading your message, I see I have the same potential problem, so I'm building a new nitrous fuel distribution block with a fuel return after that block, but feeding the fuel rail from that same end. This way, the nitrous fuel connections will be upstream of the bypass point and the stock fuel rail will be at the same pressure.

Thanks for sharing your experiences with the forum. Oh, and please keep your car......


Last edited by grey99max; 02-17-2009 at 06:27 PM.
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Old 02-11-2009, 09:18 AM
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good info for those who haven't yet been convinced that return style is the way to go. I'm going to sticky this.
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Old 02-16-2009, 09:21 AM
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I have built a modified fuel setup on 2k2 Maxima before using -6an lines and fittings, modified fuel sending unit by eliminating the internal fpr, aeromotive FPR, adjusted to 3 bar 44.1psi @ idle and covered the -6an ss lines in 5/8" heater hose and ziptied up.

This requires some modifying of fuel sending unit, and needs to be tapped w/ 1/8 or 1/4 npt -6an 90* fitting for return system to work. Where most people make the mistake is the internal modifications to make it feed and not bleed with the internal fpr or fuel damper as nissan calls it. I will take some pics on the next build.
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Old 02-16-2009, 10:18 PM
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96sleeper, really good information. I have two questions, at how much boost did you start having this problem? and also, im not sure which year motor you have or which fuel rail you have but i got an 04 which is the picture below, Do you think I can do this same setup you did with this fuel rail?





Which damper would be removed?

Last edited by streetzlegend; 02-16-2009 at 10:40 PM.
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Old 02-17-2009, 02:45 PM
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I only had this problem when I went to the 2.70 pulley, 11-12 psi for me with the intercooler. That fuel rail is different from mine. My engine was an 02. I left the damper with the fuel inlet on it. I removed the other one that was bolted onto the end of the rail. Mine looked just like the picture I drew. That rail design would not work as well for a return setup. It might be hard for the adapter and fuel line to fit under the rail in that location.
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Old 02-19-2009, 03:50 PM
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96sleeper do you have any pictures of your modified fuel rail? i'm doing a 3.5 swap now....should i do a return style setup? or is this mostly for F/I cars?
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Old 02-19-2009, 04:59 PM
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Originally Posted by streetzlegend View Post
96sleeper, really good information. I have two questions, at how much boost did you start having this problem? and also, im not sure which year motor you have or which fuel rail you have but i got an 04 which is the picture below, Do you think I can do this same setup you did with this fuel rail?

Which damper would be removed?


Here's a 2002-03 fuel rail. It has removeable dampeners on both rails and the fuel feed line on one side - and since I have two, it looks like I can put feed hoses on both rails and "Y" them together. That's my plan when the weather gets a little better.

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Old 02-19-2009, 05:19 PM
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Thanx for the picture, it looks like i'll have to upgrade the fuel rail before i increase my power. you got any extra fuel rails similar to that Harold?

one_fast_max:
I really doubt your going to have issues if you stay n/a, so if you already setup the fuel system how everyone else does, then leave it as it (my recommendation).
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Old 02-19-2009, 05:24 PM
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Originally Posted by streetzlegend View Post
Thanx for the picture, it looks like i'll have to upgrade the fuel rail before i increase my power. you got any extra fuel rails similar to that Harold?

Sorry, nope - one on the car, one on the bench - and it's gonna be short the inlet hose soon...

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Old 02-19-2009, 05:53 PM
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ok... thanks streetzlegend! i plan on a supercharger in the future so i will just change the fuel setup before i do that...
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Old 02-19-2009, 06:14 PM
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Originally Posted by one_fast_max View Post
96sleeper do you have any pictures of your modified fuel rail? i'm doing a 3.5 swap now....should i do a return style setup? or is this mostly for F/I cars?
I don't have any pictures with me, I am in Wisconsin this week for work. My car ran great N/A so I would leave it returnless and not worry about it. Many people have done it that way and it runs fine. I think the return style works better once you get a high flow fuel pump, large injectors, and start running forced induction.
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Old 02-19-2009, 08:33 PM
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ok! awesome info! thanks! i'm hoping i can break a 12 sec with my 3.5 like you did
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Old 03-08-2009, 07:27 PM
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Fuel system updated - finally

I've been working my way through the entire fuel system over the last few months - it's been deep winter here. I was having serious problems with running leaner and leaner since the fall of last year - typically 18:1 when spraying as low as a 75-shot.

I put in another new Walbro GSS342 255lph pump with battery-direct wiring - that didn't help.

Then I decided to replace everything in the fuel system from the fuel line onward. I installed a huge Aeromotive fuel filter, changed all the lines to 3/8"ID Gates fuel hoses, left the new Aero regulator - but changed where it was connected. built a new 3-port nitrous/fuel manifold, modified the 2002 fuel rail to have feed hoses on both the front and back portions of the rail, and connected the Aero regulator between the 3-port manifold and the lines to the fuel rails - to keep the pressure there at the set point. I measured the 300ZXTT filter i've used for years (except this one had maybe 250 miles on it) and found the inlet was only 1/4" ID..... ???

Most photos don't show the 3rd fuel port, but right now it's connected to an unpowered solenoid through a 4AN - 4AN line for the next step in spraying.

Last night was the first time I took out the car with all the changes made and fresh fuel and hot nitrous bottle loaded on board. Jetting was 75-shot and 100-shot for the first two stages. This car feels very strong with the 75-shot alone, and when I hit the second stage, if felt like an afterburner kicked on - darn near left the road in a heartbeat. Plugs looked fine - for a change, they all looked identical ! (at least the front bank did). I think the idea of regulating the fuel pressure right at the fuel rail pays BIG dividends when spraying. A/F stayed right at 12:1 when N/A and through all the nitrous stages. Finally....

New filter: http://www.aeromotiveinc.com/products.php?prod=158

More pix:



http://i48.photobucket.com/albums/f2...9/DSCN0730.jpg
http://i48.photobucket.com/albums/f2...9/DSCN0731.jpg
http://i48.photobucket.com/albums/f2...9/DSCN0732.jpg

http://i48.photobucket.com/albums/f2...9/DSCN0734.jpg
http://i48.photobucket.com/albums/f2...9/DSCN0735.jpg
http://i48.photobucket.com/albums/f2...9/DSCN0736.jpg

300ZXTT filter: Is this too small ??




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Old 03-12-2009, 11:21 AM
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Do any of you have pictures of your fuel rail after being modified? Just looking for some reference before I start.
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Old 03-12-2009, 12:01 PM
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Originally Posted by sparks03max View Post
Do any of you have pictures of your fuel rail after being modified? Just looking for some reference before I start.
In my case, if you look at my Post #9 up above, you will see a 2003 fuel rail complete with stock injectors. There is a fuel hose at the inlet of one rail, and a damper on the same end of the other (front) fuel rail.

I took off the damper, took off a fuel hose from another fuel rail, and bolted the new hose to where the damper came off. Presto, two fuel hoses feeding the fuel rail. (this only works on 2002-2003 fuel rails).
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Old 03-12-2009, 01:10 PM
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Originally Posted by grey99max View Post
In my case, if you look at my Post #9 up above, you will see a 2003 fuel rail complete with stock injectors. There is a fuel hose at the inlet of one rail, and a damper on the same end of the other (front) fuel rail.

I took off the damper, took off a fuel hose from another fuel rail, and bolted the new hose to where the damper came off. Presto, two fuel hoses feeding the fuel rail. (this only works on 2002-2003 fuel rails).
Ok so you just used that 2nd damper for your return line with the FPR inline, right? Seems easy enough.
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Old 03-12-2009, 01:39 PM
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Originally Posted by sparks03max View Post
Ok so you just used that 2nd damper for your return line with the FPR inline, right? Seems easy enough.
My setup is a little more complicated because I built a 3-port fuel manifold before the dual inlets to the fuel rail, and connected the FPR at the midpoint where those two join. I don't flow fuel through the rail like the OP does - just provide a feed hose for both side of the fuel rail. There's more pix in the "Fuel SYstem Updated - Finally" post above...
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Old 04-05-2009, 05:48 PM
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Return-style system is the best ?

For what it's worth - I was watching the SPIKE channel this morning, the Muscle Cars segment where they were rebuilding a Dodge Challenger left over from Fast and Furious and installing a new Hemi - the builder was describing the new fuel system they built for the car, using a new fuel pickup in the tank which was 1/2" ID tubing. They ran a 1/2" stainless line up to the front and ran a 1/4" stainless return line back to the tank "to keep the fuel cooler and to reduce vapor lock" for the fuel-hungry Hemi. Return-type systems seem to be important for the big boys...

The part about preventing vapor lock seems to be another good point to me - plus the extra bonus of keeping the fuel cooler.

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Old 04-14-2009, 10:58 AM
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i have had a fuel rail like this on my setup from a murano I took the dampner off and attched a fuel line there works great!!! I stay rich as can be under boost.. on my 3.5l did you guys know that you can use ford injectors if they are high impedence.. I have 2003 ford mustang supercharged injectors in my engine and they work great.. they are 410CC
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Old 04-29-2009, 12:22 PM
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hey 96sleeper, was looking over your diagram, the drawing of the rails is just a general picture right? because the 3.5 rail only has one cross over tube connecting both sides.
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Old 09-15-2009, 08:08 AM
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Just to inform everyone, So far I have not had any issues with my 2004+ 3.5 fuel rail, im getting plenty fuel (little too much actually), with the traditional 3.5swap fuel plumbing. Perhaps this rail flows better, but it works for me. This is at 15-20psi of boost btw.
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Old 11-18-2010, 03:36 PM
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^^^ that's very good to know since I just swapped in a 05 motor and plan on doing a RMT. I'd rather leave my fuel rail how it is unless it's absolutly necessary to modify it.
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Old 02-22-2011, 01:19 PM
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The ebay nissan fuel rail adapters work on VQ rails too... I bought one that has a -6AN fitting, like so....
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