Author Topic: injector impedance????  (Read 1520 times)

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Offline zyber_kreazian

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injector impedance????
« on: Jul 9, 2012, 10:51PM »
help pls......

i have a u13 sr20det awd.

apparently i need to kno the impedance of the injectors so i can buy some to match.....

so what is the impedance on my car???

and what cc injectors do i need to get 200kwatw with my t28 bb

thanks.

Offline noss

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Re: injector impedance????
« Reply #1 on: Jul 30, 2012, 01:29PM »
i'm pretty sure this is answered somewhere else on the site, but its shitting me seeing this unanswered thread.

they are side feed, high impedance. and yes, you do need to know the impedance. sr20's being what they are though, you should be able to pick up aftermarket units anywhere so you shouldn't even have to think about this, you should just tick the box that says 'sr20det' when you're ordering. don't fuck around with 2nd hand injectors from some other car with different plugs and what not if you can get direct fit aftermarket units. one thing i love about not owning a u12 anymore is that for a small price premium, i can buy stuff that just bolts right in.

a very basic rule of thumb for inejctor sizing is

flow in cc / 5 = hp per injector (at the crank)

so if you wanted to start with the power of your car, assuming your 200kw is at the wheels, we'll allow for 30kw in drivetrain losses and go from there, multiplying by 1.34 to get hp

((power at crank in kw * 1.34) / 4) * 5


((230 * 1.34) / 4) * 5 = 385cc injectors

that would be at 100% duty cycle however, so you want to add a bit of meat. a maximum of 80% duty is generally pretty good. so you'd want to multiply the figure by the inverse of 80% - the inverse of 0.8 is 1.25

therefore 385 * 1.25 = 481.25cc injector size @ 80% duty cycle

easiest to grab around that size is 500cc
« Last Edit: Jul 30, 2012, 01:32PM by noss »

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Offline awd2.0t

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Re: injector impedance????
« Reply #2 on: Jul 30, 2012, 03:06PM »
I've got some Nippon Denso injectors that are 7XX, they've been in the draw for so long I've forgotten.  I had a similar set up with the T28, exhaust, FMIC etc.  I was slowly gathering parts so I could extract more power until the car got hit from behind

So the short story is I have a set if you want them just make an offer.  With these you'd be running at around 50% duty which gives you a bit more room if you decide you want more power.

Offline awd2.0t

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Re: injector impedance????
« Reply #3 on: Jul 30, 2012, 03:11PM »
I just looked up my for sale thread, the injectors are 740cc