fuel return

chendaxian888

Hi guy question
fuel retrn is must for e85
does fuel return necessary for 93?
does fuel return necessary for turbo 93?
will the engine more reliable without it?
does GTR come with fuel return?

Spooler

Yes, you need a fuel return system, upgraded fuel pump or pumps, and upgraded injectors. Depending on what whp you want will dictate what you will need.

gomer_110

For just 93 no it's not needed. Our cars need premium fuel from the factory which in Ohio where you say you're from, premium is 93. If it was required just for an unmodified car, Nissan would have included it.

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'11 370Z Nismo #528 Fast Intentions | Stillen | Motordyne | Uprev | CSF | Zspeed | Z1 Motorsports | AST | Swift | SPC | SPL | Whiteline | Hotchkis | Bride | Schroth | Robispec | Cusco | Nismo | Volk | Forgestar | Hoosier | RJM
'17 Titan Bone Stock

Spooler

He has a turbo car. FI kit I think it is.

THE BULL

This answer might be a bit more technical than you can understand.

Depending on your goals will determine if so.

The main issue with return less systems is the size of the hose and folks attempts at solving fuel pressure issues.

The issue is not fuel pressure but fuel flow and the now lack of there of.

With the introducction of surge tanks we see that even return less systems dont lean out any more.

Without a pressurized chamber the oem feed line just dries out as it demands more flow however due to the size + lenght of this hose fuel pressure just bleeds off the regulator. Upon demand the regulator closes however since theres really barely any volume then a lean condition presents itself.

I did a recent test in my fuel injector cleaner machine. Upgrading the pump from a 150 lph to a 240lph and while I did see some pressure increase when I try to flow high flowing injectors the pressure drops tremendously.

Now If I add a plastic chamber in the middle of the pressurized line I dont get as low of a drop. If I could squeeze a bigger chamber there would be little to no pressure drop in that setup.

This transitions into real life scenarios.

Return style works in keeping fuel flowing through the system by having a regulator outside of the tank and keeping the rail with as much of a direct flow from pump to rail as possible. The problem with return style is that it too can be affected by flow.

What you see is folks blowing ridiculous money on dual/triple pumps because that's what everyone does and have been doing for years. Surge tanks only started trending because the looks of the system were finally understood by the regular population.

A simple surge tank can keep you at a single pump for some time. A dual pump with a surge tank will over kill most VHRs. (900-1000whp has been a safe limit for a while)

You usually see these types of issues with air as well.
Turbo single cylinders suffer from this flow as well, the turbo is just simply not able to create boost on command without enough exhaust flow. By adding a pressure chamber on the cold side you see a much smoother flow and no loss of pressures when you dont want them.

phunk

In short, the purpose of a return fuel system is to regulate fuel pressure at the rails, rather than at the pump. This provides more stable and consistent fuel pressure as it remains under better control.

Explained; There is a fuel pressure drop that occurs across the fuel line. The longer the line, the smaller the line, or the greater the flow; the more pressure drop across a fuel line. At stock power levels, the flow through the stock fuel line is minimal as the fuel flow matches fuel consumption and low horsepower means low fuel consumption.

As power increases, fuel flow increases, and this causes pressure to drop. With a stock returnless system, you are regulating fuel pump pressure, but not rail pressure. Your rail pressure result will be pump pressure minus your feed line pressure drop, which increases as power/flow increases. Your pump is always capped off at 52psi by the stock regulator.

The reason for a return system is to regulate pressure at the engine, which is more consistent and reliable. Now your fuel rail pressure will be consistently controlled by the regulator (opposed to variable pressure drop), and the line pressure drop in the fuel feed line will be absorbed by the fuel pump. So if you want 52psi in the rails, the pump can operate at rail pressure plus line pressure drop for a total higher pressure to accommodate the end result of ideal rail pressure.

A return fuel system like the CJM system benefits you from a few things... For 1, most obvious, it is a return system, so you are regulating rail pressure rather than pump pressure. 2, you have increased fuel feed line size, which reduces the overall pressure drop to begin with, and helps utilize the peak capabilities of the fuel pump. 3, an inline fuel filter allows you to bypass the stock one, and for use with E85 this is beneficial as the stock cellulose fuel filter will swell with moisture introduced by E85 and more quickly become a larger source of pressure drop. 4, the provided adjustable regulator has a vacuum port for if you or your tuner wish to change from a static fuel rail pressure to a 1:1 pressure.. this means the rail pressure will be a constant differential from the intake manifold pressure, which makes better use of the fuel injectors.

For the surge canister stuff mentioned above... that is about protecting you from sharp and sudden pressure drops as a result of fuel pump starvation caused by fuel sloshing about in the tank. These products and this fuel slosh issue is, for the most part, entirely unrelated to return fuel systems. Surge tanks have been around forever, and you can use them with or without return fuel systems. Surge tanks allow a returnless or a return fuel system to continue to function properly when the fuel inside the tank sloshes around during extreme driving.


Questions answered:
fuel retrn is must for e85 : No.
does fuel return necessary for 93? : No.
does fuel return necessary for turbo 93? : No.
will the engine more reliable without it? : No.
does GTR come with fuel return? : Yes

A return system is never required, you can always work without it. As your fuel consumption/flow increase, you become better and better off to have one.

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chendaxian888

turbo kit still making, will be done like a month, I am looking for the supporting mod for turbo kit now

chendaxian888

Got it! very good answer!

THE BULL

Wouldnt a 2 liter surge tank with a 6-8 AN hose that feeds the rails help with volume and pressure?

As the engine demands more volume, wouldn't then this volume be satisfied being that there is already 2 liter of pressurized fuel in the surge that can be refilled by the pump once WOT even has ended?

phunk

A surge tank with its own fuel pump(s) providing the rails with pressure reduces or eliminates fuel slosh starvation. If you were to also run a larger fuel line from the surge tank to the rails, you could reduce the pressure drop between the surge tank and the rails. You do need to regulate the new system though, and you do need to devise a technique to keep the original in-tank venturi system operational, since plumbing the stock fuel pump module to fill a surge canister would relieve the original sending unit from pressure thus eliminating the backpressure required to keep the venturis working. If you are adding a new fuel line from the surge tank to the rails anyway, seems like youd be best off to just put the new regulator in the engine bay as you will now have 2 fuel lines and thus can also have a return system, killing 2 birds with one stone. There are ways to make surge canisters work in vehicles with backpressure venturis, but it is a little overcomplicated and that can make it finicky and depend on installation conditions that can become a hassle in certain applications. This is why, for our product line, we eventually strayed away from this overly complex arrangement. We ended up solving all the fuel slosh starvation issues directly at the primary fuel sending unit in the fuel tank, with no secondary fuel system required. We do still call it a surge tank, but it actually just replaces the original fuel sending unit and the entire venturi system. We did the separate surge canister thing for like 10 years, and while it works for the majority of customers, it also painted some of them into a corner when they needed to make custom changes.

To answer your question in short: Yes, a surge tank with a big feed line to the rails can solve issues. But unfortunately the integration is more complex than it sounds and can be finicky with the backpressure side venturi system the Z uses. I wouldnt generally recommend this route to someone unless they have a strong understanding of fuel system dynamics so that they know what they are up against and how to sort out the less obvious issues when encountered. But sure, if you set it up right and dial it in, it could very possibly handle your needs.

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avioni

questions.

does the external regulator on a return system go before or after the fuel rail? if after then how is that installed with oem fuel rails? if before how does it work?

is the fuel dampener connected to the rubber hose that goes to the firewall needed? i have an issue where the dampener line hits the throttle cause of stillen plenum and i bent the line down and it kinked a bit. solution would be to install a plate with AN fitting replacing the dampener and a line to the firewall. but 2 reasons why i havent done it. dont know if the dampener is required and cant find anyone selling a line that would clip to the firewall line and have an AN fitting on the other end.

phunk

A regulator can go before or after a rail, it is up to the installer or the design of the kit. The regulator works by bleeding pressure from the fuel system. You can tap into the fuel system anywhere you wish to feed a regulator. Ideally the regulator is spliced in close to the rails or off the rails, so that it is regulating true rail pressure or as close as possible to rail pressure.

In CJM kits with billet rails, the regulator is after the rails. In CJM kits with stock rails for VHR, the regulator is before the rails. This adapter is used to splice fuel for a regulator off the fuel rail inlet tube at the front of the engine : https://cj-motorsports.com/products/...p-4-way-2-bolt

Fuel dampers are highly recommended. The more the merrier, but we have found in most cases that VQs with a damper on each rail do well enough without the 3rd one on the feed line.

https://cj-motorsports.com/products/...output-fitting
drop down selection 320.0086 is an adapter that allows -6 connection to the stock fuel pipe.

https://cj-motorsports.com/products/...-nissan-2-bolt
this is a real simple adapter if you want to replace the damper with a AN adapter to make a new feed line and dont need the outlet for a regulator/return like the 4-way adapter I linked above.

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THE BULL

Dampers in the aftermarket fuel area were non-existent up until recently. My awareness of them started with the VQ. Then you started to see them more and more.

For what I understand these remedy an effect of resonance and pulse in the rails from every closing of each injector, the first one absorbing any pump related pulses that could resonate in a way it affects airfuels

Would this mean ANY decent fuel system HAS to have this or is this particularly related to return less systems, types of injectors and type of firing of these injectors.

phunk

As far as I know, we might have been the first aftermarket company to integrate dampers to complete aftermarket fuel systems and directly into aftermarket rails. We have been doing it for over 10 years. When we started, the only thing on the market we had seen was a Marren damper, universal application part.

It wasn't without reason. We were having unidentified issues for some years without understanding why. Eventually we got it sorted out. Yes the fuel pressure pulsation is basically a pressure resonance of the fuel injectors closing. The pulsations can cause audible noise and have big side effects on the fuel injection system at resonant frequencies, occurring at particular windows of engine speed.

Soft rubber fuel lines have dampening qualities. We always used hardpipe and PTFE, which is why were had problems earlier on while everyone else was still using rubber core stainless braided hoses. I am sure some fuel injectors exacerbate the issue as well, if they have a more aggressive or harsh closing of their valve. Larger injectors probably contribute as well.

Does any decent fuel system have to have them? It certainly wont hurt to lower the amplitude of the pulsations with a damper or 2 or 3. If your car has a lot of soft fuel line, it may already have adequate inherent dampening. At this point, where fuel rails are being CNC machined per application lots of the time, its difficult to justify eliminating them. You might just bottom them out at high boost with big fuel pressure, but that wasnt really when pulsations were causing grief. Its more of a problem at steady engine speeds where you find and hold resonant frequencies that wreak havoc and cause drivability issues. In the years that we struggled with pulsation issues, we never saw a problem under meaningful power, it was always just an issue when cruising at steady engine speeds.

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