Injector Sizes

**nathanblaise** · 19-01-2017, 23:00

Hi all,

Just looking at injector sizes for a duratec build (dth jenvey throttle bodies, retroford exhaust, standard cams/engine) and from everything I've read around 330cc injectors will be good to go. If possible i would like to be able to reuse the injectors I buy when going to a 262hp type build - for the later stage I'll need somewhere in the region of 400cc.

My question is - am I able to buy the larger injectors for the next stage and still get a reasonable idle/tune for the first iteration of the build? I've tried to read up as much as I can but can't seem to find anything conclusive. Some posts say the idle will be bad, some say it can be tuned out.

Does anyone have experience in this area? I'll be using a Link g4+ atom ECU.

All the best,
Gareth

**katana** · 19-01-2017, 23:10

No direct experience but I know guys running some fairly extreme turbo streetbikes - 1300cc making potentially 6-700hp @ 40+psi boost and using 1200 & 1500cc RC injectors and they idle just fine. If you can find suitable injectors even 500cc flow they will still idle down with reasonable flow and run cooler as their duty cycle will be lower. Low impedence / high flow used to be hard to find but not these days - don't sweat it, its likely a non problem.

**theduck** · 20-01-2017, 13:03

You'd be fine running that kind of size injector. Should be able to pick up Subaru "baby blue" WRX injectors for fairly sensible money and they would be ideal for your needs.

**Sultzi** · 20-01-2017, 13:20

With today's ecu's you dont have problem with idle, even with big injectors like 1700cc work fine on small engines. Is all about the ecu and quality injectors.

**Graham** · 20-01-2017, 18:54

ive run 1000cc per minute injectors and the engine idled like standard, most modern injectors have good enough spray patterns that as long as the ecu is mapped correctly dont give issues with idling

**Leafy** · 20-01-2017, 23:53

Just stick with an EV14 based injector from a reputable vendor that does proper flow balancing (ID, FIC, DW). If your setup uses the stock rail, you can use standard long (60mm) EV14s. You just have to notch the back of the injector for the rail clips to work.

From left to right, unmodded, modded, stock.

**nathanblaise** · 21-01-2017, 21:29

Hi all, thanks for the responses , good info and has really helped me out knowledge wise. Yep, I'll probably get some ev14 types from over here which are about $400 for a set which isn't too bad. I'm going to use a jenvey fuel rail which works with most lengths given spacers i believe. At lest this is one thing i won't have to change as part of a power upgrade! Cheers.

**_PauL_** · 26-01-2017, 15:54

high impedance injectors which work with more after market ecu's, also pays to learn about spray patterns and multi-hole injectors as you dont want injectors that are spraying on the port divider. I chose 660cc injectors based on the better fuel atomisation compared to 440cc which was more than enough but the fuel atomisation was poorer at idle and small throttle. avoid overly large for turbo injectors.

Funny a friend of mine runs a turbo hayabusa for the land speed record on salt in south australia, neither him or anyone else in that class is claiming silly numbers like 700hp out of a hayabusa. for instance the split case the gearbox sits in wont handle that kind of horsepower. nor will the tiny little gears or the bearing handle that much power. I could go on 8) maybe the horses are smaller in england

**theduck** · 26-01-2017, 16:58

UK tends to quote flywheel power, and I think Australia more commonly quotes at the wheel?

Even so, quick google shows this Australian was claiming 650bhp back in 2011 http://www.bikesales.com.au/news/201...-hits-502km-h/

**katana** · 26-01-2017, 19:39

Originally Posted by _PauL_

Funny a friend of mine runs a turbo hayabusa for the land speed record on salt in south australia, neither him or anyone else in that class is claiming silly numbers like 700hp out of a hayabusa. for instance the split case the gearbox sits in wont handle that kind of horsepower. nor will the tiny little gears or the bearing handle that much power. I could go on 8) maybe the horses are smaller in england

Just because you don't believe its possible, don't mean it isn't!.......https://www.youtube.com/watch?v=jQOpswi9Aqc
This guy is deffo one tinnie short of a six pack but he knows busa's and turbo's - admittedly this bike is a development tool and is a 1600cc but i've seen the dyno data and it will make over a 1000hp one day - btw that'll be at the wheel!

**nathanblaise** · 27-01-2017, 01:02

Thanks all, I,ve seen multiple injectors on my website travels but does anyone know of a good spray pattern for some jenvey dth throttle bodies? I expect there's not a huge amount in it although would like to ensure I get something that can be tuned nicely...

**_PauL_** · 27-01-2017, 04:33

yep and thats a believable claim hes making about that bike... billet engine and probably lots of other parts that start with billet +1600cc.
I would like to know more about that bike and dyno.
All Im saying is theres a lot of people saying there bikes make XXX amount of power that I know the the split crankcase cant handle.

And Ive been guilty of that very claim myself, When my mate first had his turbo busa up and running I was his test pilot of sorts for a while.
I was adamant that thing was 400hp ... reality more like 250hp still more than enough to lift the front wheel and burn rubber at the same time.