Im a little lacking in the purpose of a Fuel return system...... when you upgrade your fuel pump you will have a higher pressure fuel system right???? so if you add a return system what benefits does this give your max pressure... I understand that a return system will cycle all unused fuel back to the tank but how will not having this pose a danger.....

One with little knowledge *Me* would assume the only negative thing possible would be a rich condtiton...

Please enlighten me.....

 

Quote from gq 626:


A return fuel system with rising rate is absolutely critical when it comes to building reliably high HP F/I systems. It's a similar setup to the way APS runs their fuel system, although I think its superior, in a sense that you run all new stainless lines (except the under car feed pipe), ANS fittings, an upgraded fuel rail, and a quality rising rate FPR located in the engine compartment...AFTER the fuel rail exits...exactly the best way to do it. CJ-MOtorsports also makes another excellent return fuel system, and he includes the undercar feed pipe as well.

Without a rising rate FPR and return system, your fuel pressure will drop as boost rising. In addition, the pressure differential between the injector nozzle and the intake track will effectively cause another drop in pressure. For instance, if you running 50psi of fuel pressure at 10psi of boost...the effective fuel pressure at the tip of the injector nozzle is actually on 40psi, becuase you have 10psi of pressure "pushing back" at the nozzle.

 

So a good question is how much Fuel pressure do you need on a F/I kit????

 

So does the fuel pump supply fuel @ constant pressure in a returnless fuel system?

I can see the benefit of having a return system if the pump is supplying X psi @ constant rate and u control the pressure @ the injectors by changing the amount of fuel that is return as opposed to a returnless system which modulates the pressure by running the pump faster/slower (which would take a while to propagate through the lines).

above is an uneducated guess so it might not be @ all accurate.

 

i will be doing a tech article on fuel supply systems versus tuning systems in the 350z shortly. i get so many calls a day about this stuff that i have no choice!!

 

Im just trying to ensure I make the right choice before buying a F/I system.... I only want 330WHP initially.... have to see if my clutch will handle it...so if the upgraded fuel pump is all thats needed then ill upgrade the fuel system at a later date..... when i decide to boost more.....

Im not sure how the stock fuel system works.....thats why im asking....

 

will this system work on a stage 3 stillen with a 7th fuel injector?
Will it make more hp.

 

bump

 

You don't necessarily need a return fuel system for FI applications. You can run something similar to Vortech's FMU which is a boost dependent fuel pressure regulator. This device increases the fuel pressure as manifold pressure rises, ensuring that you get more fuel under boost. It is not adjustable per se like an aftermarket FPR is. BUT, you can change the pressure on it by changing the disks inside.

 

So at what hp levels do you recommend upgrading to a return fuel system?

 

yes at what levels on the turbonetics kit

 

400+rwhp is where you want to start considering it.

 

whats the highest whp i can get with the 380cc(i think) injectors that come with the kit? I've done the search a few times actually and found no definitive answer.

Other mods: ill be running utec, plenum spacer, lgtwght flywheel, modfied ses(not a 3" but better than stock still) and stillen headers
what should i expect?. Can i run 9 psi boost?

 

This is true but I feel that this also has it's short coming as exceeding efficiency of the injectors lead to bad news i.e. injector lock up. I would recommend changing to larger injectors even if using this method

 

when i do my FI Setup in a few weeks, if im using the speed force kit a little modded though, can i just run a fuel pressure regulator, big injectors, and a pump and be fine over 400 whp? also there will be an adjustable fuel tuning map on the external tuning system?

 

+1
Running 120psi of fuel pressure via Vortech FMU and their 6:1 riser is not ideal.

 

I have the Procharger with 7lb pulley and just went with the SGP return fuel system and its like night and day. I was only making around 350whp with 380cc and went ahead and upgraded to 440's and the car is sooo much smoother! Definately worth it... especially in the long run with higher boost and such.