Standard nb8b spark and fuel injector limits

mx5002 · Postby **mx5002** » Mon Dec 07, 2015 10:29 pm

Just reaching out to the knowledgeable bunch for some advice

I'm in the process of putting together a built hi compression N/A vvt motor to replace my standard vvt motor. I guess I'm hoping for around 115-120ish rwkw. Would the standard injectors /ignition be capable of that? Or is there a better alternative I should be looking at piecing together. The car runs a ps1000 ecu. Only looking at running 98 unleaded. No e85 at this stage

Thanks

Postby **NitroDann** » Mon Dec 07, 2015 10:33 pm

Dynamic compression of 30:1 for spark on 98. At a guess 25:1 on E85. Using plug gaps of 0.6mm.

160whp for fuel injectors on 98, or 120hp on E85 at stock fuel pressure.

mx5002 · Postby **mx5002** » Mon Dec 07, 2015 10:39 pm

So fast Dann.

Thanks

So I'll be looking at some larger injectors then.

rascal · Postby **rascal** » Tue Dec 08, 2015 6:51 am

mx5002 wrote:So I'll be looking at some larger injectors then.

Not necessarily so.
115-120rwkw = 153-160whp which is within Dan's limit for 98....

You could bump up the fuel pressure a touch to give yourself some headroom if you were closer to 120 than 115.....

mx5002 · Postby **mx5002** » Tue Dec 08, 2015 8:57 am

Would it not be better to have a larger injector that would leave some headroom?

I've never really played around with injector sizes etc before.

rascal · Postby **rascal** » Tue Dec 08, 2015 9:53 am

Depends on your definition of better..

Going bigger when you may not need to, is not better with respect to time, effort and money considerations.
However, fitting larger injectors even if not needed is better for peace of mind respects.

fwiw, I have similar plans to you for my NB, and plan to be dynoing early next year. (though mine will prob only be around 110kw)
I will be leaving the original injectors in there, but will have spare larger injectors with me just in case.
If I find I'm running out of fuel on the dyno, then its a pretty easy job to swap them over and continue.

If I don't need them, then I can return the larger injectors for a refund, or onsell, as still brand new unopened.

zossy1 · Postby **zossy1** » Tue Dec 08, 2015 10:23 am

RX8 injectors are PNP and are dirt cheap. In the context of a 120rwkw build, they are a tiny investment.

EDIT - if you burn $600-$900 worth of dyno time because you run out of injector capacity, you will kick yourself for not coughing up $200 for a set of injectors.

mx5002 · Postby **mx5002** » Tue Dec 08, 2015 11:26 am

My thoughts exactly zossy.
Just wish i was could stretch the budget for itb's like you guys.

Going to run my Flat top mani with a skunk2 TB.

Postby **beavis** » Tue Dec 08, 2015 11:36 am

I'd just go with RX8 injectors and not have to worry about it. enough room to go either 98 or e85 at the ~160hp level.

mx5002 · Postby **mx5002** » Tue Dec 08, 2015 6:12 pm

Just looking at them now. There's a few types of rx8 injectors. Are they all suitable?

zossy1 · Postby **zossy1** » Tue Dec 08, 2015 7:29 pm

The yellow denso ones are what you're after - 195500-4450. I know there are some knock offs but for what they cost, I'd be sticking with genuine denso units.