Injectors - How Big To Go And Drawbacks

[wannabeslida]

Am looking at doing a few upgrades over the next 12 months to my newly aquired GTR. Was looking at just getting current injectors cleaned/flowed etc but then thought, why not use the clean money towards upgrading them?

Don't want to fork out upgrading Injectors twice if I don't get large enough ones the first time. Also hesitant to get too large as worried it will cause it to run rough and loose the adjustability down low? Is this my misconception or real?

Interested to know what size to go for, I realise that it would be dependant on what I have planned and if I upgrade it will require a tune to adjust. At this stage, being put on are 3 inch exhaust, pod filter setup and yet to be worked out, larger single turbo?

Second query if anyone wants to enlighten me, what price roughly are injectors for GTR, 800cc or 1000cc seems to be where I will be aiming?

Have seen on EBay 7993894339 - Nissan 800cc Direct Fit Top Feed RB26DETT INJECTORS. Buy now for set of 6 US$360, will do 1000cc for same price.

These are also listed starting at $299 and dont attact many bidders so would be mailed to Aus for US$330. Any better deals around?

Thanks

[grim32]

1000cc injectors are huge, what sort of power are you looking for?

[Suspense]

from my understanding injectors run off a PErcentage readout from the ECU, so the larger the injector for or use, the more inaccurate the injector would be, hence i would assume it is best not to over size...

[The Dan]

You will need to remap your computer or run aftermarket gear to use bigger injectors.

THIS IS THE FORMULA YOU WILL NEED TO WORK IT OUT:

Work out the horsepower you want to achieve

DIVIDE that figure by the number of cylinders you have

Then MULTIPLY that figure by 5.

This will give you the approx CC/Min rating you will require.

EG. GTR wanting 800 (Engine) HP will require

(800 / 6) X 5 = ~ 666 cc/min injectors

Then add 50cc/min for good measure so that you wont max them out.

The trick is to come up with an engine horsepower figure that is approx. 20% more than what you really want.

Hope this helps.

[The Dan]

Also....DO NOT GO TOO BIG OTHERWISE YOU WILL HAVE TUNE PROBLEMS. As close to what you want as possible....don't get 750's when you only need 550's.

[TommO]

Also....DO NOT GO TOO BIG OTHERWISE YOU WILL HAVE TUNE PROBLEMS. As close to what you want as possible....don't get 750's when you only need 550's.

<{POST_SNAPBACK}>

Care to elaborate why and how it will affect the driving of the car?

I've got a couple of mates running 1000cc injectors, who are currently not running anywhere near the potential of them (low boost tune - so honestly only using about 550cc worth of injector), and the cars all drive very nicely, perform well off / on boost, and don't seem to have ANY injector based problems. Both have Microtechs.

[The Dan]

Ahhh, the good old microguess. I shouldn't really need to explain myself. Problems are too much fuel as the larger injectors are harder to tune to smaller amounts.

What cars do these mates of yours have?

[TommO]

R33 GTS-T, Lancer GSR... both making fairly big power, but both drive great off boost and are smooth. I agree with your thoughts on the Microwreck but if it produces good results, then I anything can

I understand about the "too much fuel" comment, but is the only thing that would affect is fuel economy? Would it affect driving too? Just these guys have got their AFRs where they want them.

Just trying to work out exactly what the effects of going too big injectors for your application is, as i've always wondered this myself.

[ferni]

You will need to remap your computer or run aftermarket gear to use bigger injectors.

THIS IS THE FORMULA YOU WILL NEED TO WORK IT OUT:

Work out the horsepower you want to achieve

DIVIDE that figure by the number of cylinders you have

Then MULTIPLY that figure by 5.

This will give you the approx CC/Min rating you will require.

EG. GTR wanting 800 (Engine) HP will require

(800 / 6) X 5 = ~ 666 cc/min injectors

Then add 50cc/min for good measure so that you wont max them out.

The trick is to come up with an engine horsepower figure that is approx. 20% more than what you really want.

Hope this helps.

<{POST_SNAPBACK}>

This calculation means standard 444cc GTR injectors are good for 533HP(400KW) at the flywheel? is that right?

[Fitzpatrick Speed Works]

I woulndnt run an 800hp skyline on 666cc injectors thats for sure. You will need an aftermarket computer for anything larger than 550cc injectors. With an aftermarket computer how a big injector behaves has a lot to do with the tuner and how much time they put into loading injector inputs and how finely they tune the opeining of an injector, if someone does a rough job you will get a rough idling car and other associated problems. To clear up for those who dont undertand an injector is operated from the computer through a hot wire (power) that powers the injector diaphram which inturn opens the a needle off a seat and the fuel pressure behind the injector sprays fuel through the injector past the needle and into the inlet. The computer tunes how long of time the injector is feed power to lift the needle off the seat. An injectors size is detemined buy the area of the needle ie if you have one needle at .2mm in one injector and have a twin pintle design with 1.5mm needles the second is going to larger. The computer controls smaller injectors better as if the injector is left open too long there isnt as big of an opeing letting fuel through, however the tuner of an after market computer if good enough can tune a big injector as effectively as any other, it comes down to time and experience as we are talking 100's and 1000s of a second in injector timing. Hope this clear it up for people.

The stuff I have seen on american ebay for cheap prices doesnt look that good and I dont think you would be recieving the item you are paying for, as a rule of thumb in Austrlalain dollars for six that are a direct fit you will pay the same as the size. Ie. 600cc around $600, 1000cc around $1000. This is for quality stuff that will fit the application.

[The Dan]

I woulndnt run an 800hp skyline on 666cc injectors thats for sure. You will need an aftermarket computer for anything larger than 550cc injectors. With an aftermarket computer how a big injector behaves has a lot to do with the tuner and how much time they put into loading injector inputs and how finely they tune the opeining of an injector, if someone does a rough job you will get a rough idling car and other associated problems. To clear up for those who dont undertand an injector is operated from the computer through a hot wire (power) that powers the injector diaphram which inturn opens the a needle off a seat and the fuel pressure behind the injector sprays fuel through the injector past the needle and into the inlet. The computer tunes how long of time the injector is feed power to lift the needle off the seat. An injectors size is detemined buy the area of the needle ie if you have one needle at .2mm in one injector and have a twin pintle design with 1.5mm needles the second is going to larger. The computer controls smaller injectors better as if the injector is left open too long there isnt as big of an opeing letting fuel through, however the tuner of an after market computer if good enough can tune a big injector as effectively as any other, it comes down to time and experience as we are talking 100's and 1000s of a second in injector timing. Hope this clear it up for people.

The stuff I have seen on american ebay for cheap prices doesnt look that good and I dont think you would be recieving the item you are paying for, as a rule of thumb in Austrlalain dollars for six that are a direct fit you will pay the same as the size. Ie. 600cc around $600, 1000cc around $1000. This is for quality stuff that will fit the application.

<{POST_SNAPBACK}>

No-one said anything about running 666cc/min injectors on an 800hp GTR. I would pick something like a 720. As I stated....go up another 50 cc or so...or to the next available size.

What I was getting at was don't go out and buy 1000cc injectors if you are only aiming at 300rwkw. There is an equation to work it out and I have provided it.

In answer to the previous statement : yes, the standard GTR injectors will be good for around 530 engine hp.

[Duncan]

actually standard gtr injectors are good for 511rwhp

[Duncan]

for about 8 weeks

[wannabeslida]

Thanks all for responding to my query. I will have to think a bit more about the target power figure and then work out the injector required.

I might aim for 720 instead of going all out on 1000cc.

Thanks again.