stock q's and sizing injectors for rb25

[bryan01]

i pulled off my stock fuel rail and injectors to transfer them from the old plenum to the new plenum and found something a little frightening. the, what looks like, ceramic sheath that's surrounds each injector tip and hooks over the end as if to hold it in place was broken off in one way or another on most of them. one of them broke off as i removed it. Does this piece of the injector actually have a purpose? b/c i dont think it holds anything in place, the injectors are 1 piece and are bolted down, and it doesnt seem to affect fuel flow. is it just meant to insulate the tips from the plenum? of course i was very worried about having ran the car with these injectors. at first i thought i had broken off the sparkplug-looking-arc-hook-tips of the sheath the last time i removed the intake plenum, which would have been very bad since i then reinstalled it and ran it. i mean what if i had cracked one and it fell off during the 10 mins i had it running? not good. but the injectors dont stick out at all from the plenum so i couldnt have broken them. i felt a little better knowing whatever damage was done was done before i got the motor. (right?, this is the point that you reassure me) hopefully it was done with the injectors out of the engine and the little ceramic pieces didnt end up inside the motor. at least it's not metal thou.

 

either way, i'm very concerend with putting them back in, even if i removed the sheath's so they wouldnt break further.

 

i found some injector size calculators and such and was wondering what other people were running. the injector calculators need a stock fuel rail pressure number as one of the values. anyone know this for the rb25 series 1? as of now the motor is stock an has a huge fmic and exhaust. i didnt plan on modifiying it before getting it completley running stock, but looks like i might have to. my friend has a megasquirt i could use to control the bigger injectors, but i need advise on what size to get. i checked and people are running anywhere from 550cc to 800. any thoughts?

[bryan01]

i know i'm answering some of my own questions, but here's some info i found:

 

http://www.rceng.com/technical.htm

 

http://z31.com/software/injector.pl

 

http://www.racetronix.com/

 

on racetronix they sell (6) 55#(577cc) or 65#(682cc) injectors for 330$/set and other guys on here said they're using them and work well. according to the z31 calculator, backed up by the rc formulas, using .65 bsfc and 80% duty cycle, 55#'s are good for 407 crank hp and 65#'s are good for 478 crank hp. of course these hp #'s change when you assume different initial values, but those were average #'s to start with according to the references to get a ballpark injector size. (this also assumes you're not playing around with fuel pressure and that the injectors are delivering what they're designed to deliver)

 

i think i'm going to go with the 65# ones to give me some room to grow. ZUL8R on the board dyno'd at 300rwhp w/ 555's and a t3t4 turbo at 15psi. assuming a 20% loss thats 380hp at the crank with a mildly modded rb25. anymore than that and you're pushing the 55#'s (either above 80% cycles or more pressure than they're designed to flow per pulse). and then you have the 75#'s, but they just seem to be overkill for what i'm doing at this point.

 

just to make sure, do i need to do anything special considering they're low impediance (2 ohm) injectors? whats stock, low or high? ... also do i need a top fed fuel rail for these? thanks for the hlp

[url=http://www.racetronix.com/][/url]