What Injector Size To Go?

[Randon_I_Am]

My 34gtt is at 215kw atm with the following mods

3"stainless xforce turbo back exhaust

NIStune ecu

Greddy Profec II Boost controller

Blitz Return flow FMIC

K&N filter in standard air box

wallbro fuel pump

It's now time to upgrade the turbo and injectors

I'm looking to get 250+kw but with more emphasis on responce as opposed to top end power.

So looking at NISMO injectors, my only 2 choices it seems are 480cc or 600cc. I've been told 480cc will be enough to get me to that power level but my question is, Do they have an effiency range they like to run on? is it better to have 480cc running on say 80% than it is to have 600cc running on say 50%? (figures i pulled out of my head). Considering its a street vehicle, so it'll be limping around alot on 1/4 throttle.

Also I'm considering E85 if we ever get that on pumps here...

Your thoughts would be greatly appreciated.

And any suggestions on turbo choice?

[Scradly]

GT RS on about 16psi should give you the power level your looking for.

Go the nismo 600ccs

[R31Nismoid]

480's are fine for 270rwkw

[darkhalf]

yep. 278rwkw with my R34 using these

http://forum.nistune.com/viewtopic.php?f=2...50&start=16

480's are fine for 270rwkw

[Harey]

Yes what you are saying is correct, if you are never going to go for more power then you are better to run injectors at 80% then 50% as it gives you more progression. Whether you would notice or not is another question.

I have never heard of nismo 600cc injectors to fit the rb25det neo engine? Can you post some info on these and where they can be obtained.

[Randon_I_Am]

harey : i looked back at the nismo 600ccs and you're right, although they are purple (like the 480s) they apparently will not do the rb25neo

I've read somewhere that e85 fuel needs larger injectors, as it must run richer. will the 480s be any good for that?

[Harey]

harey : i looked back at the nismo 600ccs and you're right, although they are purple (like the 480s) they apparently will not do the rb25neo

I've read somewhere that e85 fuel needs larger injectors, as it must run richer. will the 480s be any good for that?

joejoey etc uses 550cc nismo injectors on his R33 with E85 at 320rwkw, i think he said the injectors were running at 90% duty cycle. I know you cant use these injectors, but just for an example.

So do you mean 270rwkw on 98 and 290ish on E85?

[Randon_I_Am]

yeah top of the scale 270ish of 98 and then whatever e85 can bring i guess...

but i think I'd be more happy with 250ish on 98 but with better response. (not that injectors have anything to do with response)

by those numbers it looks possible but the 480s would be very close to maxing out

i don't know much about it but being a neo head, might be able to get the power slightly easier?

[Harey]

The 480s will be fine for your 98 power level but yeah if you go E85 and really push it you may be on the edge.

Other options are the siemens deka 60lb injectors which are very cheap but require wiring modifications. There is a thread on here about it.

Another option is the 650cc SARD injectors (but very pricey):

http://justjap.com/store/product.php?produ...at=0&page=1

Everyone raves about the nismo injectors, spray pattern etc.

[chrisR34GTT]

yep. 278rwkw with my R34 using these

http://forum.nistune.com/viewtopic.php?f=2...50&start=16

What duty cycle Matt? Is the car daily driven?

joejoey etc uses 550cc nismo injectors on his R33 with E85 at 320rwkw, i think he said the injectors were running at 90% duty cycle. I know you cant use these injectors, but just for an example.

So do you mean 270rwkw on 98 and 290ish on E85?

Based on the Joejoey information I threw around some figures;

260kw = 81% of 320kw

therefore, 81% of 550cc injectors = 440cc injectors running at 90% duty cycle

however, if running 480cc injectors instead (440cc/480cc = 0.916) should give you 90% duty cycle * 0.916 = 82.5% duty cycle, which is pretty efficient as I read it is desirable to be under 85%.

This is assuming all things are relative lol

Waits for flaming...

Edited April 13, 2010 by chrisR34GTT

[R31Nismoid]

Duty cycle will vary between cars/tunes and so on. Totally depends on the tuner and their decisions.

Some tune a tad richer, some a tad leaner etc. So the figures might be the same, however i'd expect some variance without question.

Also some pumps might not be getting the 100% correct voltage. Even .5v can make a difference in flow rate and then duty cycle required.

So there are some variables to consider, whilst not major, they are certainly there

[chrisR34GTT]

But ideally, if the joejoey setup was used for example, same tuner and only the injectors were changed to 480cc and tuned accordingly. A tune for 260kw should see the injectors run at around 83% duty cycle.

I'm just trying to get a feel for what duty cycle a particular power figure can attract for 480cc injectors.. I have a set and have been told that running that over 85% duty cycle promotes the chance of injector/s failure and that I should go bigger.

[conan7772]

Don't forget SK's basic guide for 6 cylinder engines.

480cc = 480 bhp or 363 kw based on 80 %

Edited April 13, 2010 by conan7772

[Harey]

~ 280rwkw on 98

[.WILKO.]

I'm running 510cc injectors at 290rwkw

from memory they was under 50%.

[Randon_I_Am]

cheers guys, The 480s will be fine for my needs

anyone had any experience with siemens injectors? they are very cheap so I'm a bit skeptical

[Harey]

They are very popular on the xr6 turbos. I think they have quite different injector pulse widths or something so require a bit of extra tuning to get right. If you want more info jump on an xr6 turbo forum they have tonnes of info on em.

[180or200]

fitted some EV14 90lb injectors to a friends 34gtt couple weeks ago, direct fit (US car plugs needed) easy to tune and cheap, $79 each on ebay!! too easy.