top feed vs side feed

[88supraTT]

just wondering if there is any performance issues with using top vs side feed injectors. compare 880cc injectors at 75-80%% flow rate, is there going to be any noticeble difference between the two? need to start going through possible setups and need enough fuel for a pt67 with a .81 turbine a/r.

already have standalone, 8 AN' feed and 6 AN return with the factory rail.

Its a 1jz

 

[Cz.]

Most people go with top feed since most aftermarket injectors are made that way and you have way more choices. As far as flow goes, it should flow as much as it's advertised so there shouldn't be a real difference between the two.

 

[apexi287]

The difference is the fact that side feed are in the rail so the fuel must flow through each before it reaches the last injector. Once you begin making big numbers and need all the fuel your pump is supplying your going to want to go with top feed to get rid of the restriction from each injector thus creating a pressure difference from the first to last injector.

 

[woodytsi]

The difference is the fact that side feed are in the rail so the fuel must flow through each before it reaches the last injector. Once you begin making big numbers and need all the fuel your pump is supplying your going to want to go with top feed to get rid of the restriction from each injector thus creating a pressure difference from the first to last injector.

couldn't you tap the rail and make it a dual feed?

 

[Bigzavs]

couldn't you tap the rail and make it a dual feed?

you could, but you're also going to be limited on the volume of fuel that the rail can hold

if you look through the stock rail, the openings are tiny

try looking down a stock rail versus a -8AN top feed rail

 

[Supracentral]

you could, but you're also going to be limited on the volume of fuel that the rail can hold

if you look through the stock rail, the openings are tiny

try looking down a stock rail versus a -8AN top feed rail

Under testing, the stock rail has been shown to support 800 +/- rwhp.

So if you are going for 800+, then upgrade, otherwise it's just for looks...

 

[funky_monkey58]

Rail volume is also very dependent on the fuel being used. For alcohol based fuels upgrading the rail is a must, for high hp.

 

[Evilempire1.3JZ-GTE]

I wouldnt go with side feed.
The top feed is cheap and so is the specific injector sizes.
The top feed rail haves 2 -8an side inlets with one pipe thread center tap outlet.
The flow is amazing when you compare it to the oem side feed.
The size of the fuel passage in the OEM rail is small and the area & flow is limited.
With top feed all your injectors get the right flow volume and get good spray patterns & pressure if your ~500hp & below oem sidefeeds are ok.

The only downside to the top feed is the rail center tap points right into the corner of the head where the forward cam angle sensor is so with the oem ECU if it is OEM will be a pain to keep that sensor and route your fuel 180° AN pipe and pipe thread to AN adapter.

In my case with my rail I had to delete the forward cam sensor shave down the mount and seal off the head. With a stand alone ECU this is no big deal because the ECU could use either cam sensor they are just 180° off from each other and the standalone ECU needs only one cam signal to operate.

 

[88supraTT]

If i go top feed with a duel 8 and center return; the problem i'm thinking about is that i only have one fuel pump and one supply off of it. Its not as easy as "Y" in another 8 off of the main supply is it or do i need to get more involved.

 

[RockPaperSwoRD]

a y connector before the rail should be fine. what fuel pump do you have?

 

[88supraTT]

walbro 255, i need to get a bigger one or run another one.

 

[Evilempire1.3JZ-GTE]

Look at the aeromotive fuel pumps because they have a chart lph HP limits etc
Mine is rated up to 800 or 1000hp turbo fuel injected na vs turbo efi vs carb they all build different hp.

I heard the wallbro is good to about 500hp never confirmed to though with recomendations.

I have an aeromotive eliminator mounted low on the back of the rear subframe.
My fuel line is all -10an

goto summit racing buy a roll of 5/8" 20' aluminum line for ~20

I have a -10 an bulkhead coupler sumped on the bottom of my tank I may get a fuel cell later.
It goes into a -10 hardline for about 2' to my fuel pump then the -10 hard line 14-15' goes all the way to my "Y" splitter into (2) -8AN braided fuel rail feeds to my top feed rail from there stand alone manament sequentially opens 750cc RC injectors.
the center tap return lines -6an feeds into aeromotive efi pressure regulator into the return line. I kept my vapor line it is a must to keep the evap system unless you goto a fuel cell and it is hooked up like factory to the jza70 co2 canister.

My setup is good for up to easily 1000hp if i ever get that crazy 2JZ or 1.5JZ is a must.

With my current injectors turbo fuel line I am good for 20+ psi 700hp setup.
All in All any cams any boost any rpm no lean spots & perfect afrs & egts. Better safe then sorry.

 

[OneJSupra]

The difference is the fact that side feed are in the rail so the fuel must flow through each before it reaches the last injector. Once you begin making big numbers and need all the fuel your pump is supplying your going to want to go with top feed to get rid of the restriction from each injector thus creating a pressure difference from the first to last injector.

You can remove some of this restrictions and increase flow to the stock rail by installing an adjustable fpr and bypassing the fd using DM fuel line kit.

 

[apexi287]

You can remove some of this restrictions and increase flow to the stock rail by installing an adjustable fpr and bypassing the fd using DM fuel line kit.

You do realize the fpr is after the rail correct? Thus wouldn't effect any flow restrictions before or in the rail. Getting different lines wouldn't decrease restrictions they are easily good for 500+ they only allow a larger quantity of fuel supply to the rail.

 

[Supracentral]

The only reason to improve flow on the return side is when you have increased flow on the feed side to the point where the existing FPR and return lines cannot manage fuel pressure effectively anymore.

Think guys - this is not rocket science.

 

[OneJSupra]

^ My thoughts exactly.

 

[apexi287]

^ My thoughts exactly.

What does your first post apply to then:dunno:. Unless I'm mistaking just bypassing the FD and replacing lines won't cause a great enough effect to warrant a larger than stock fpr. Thus still not solving the issue, or concern being side feed injectors vs. top feed.