DigitalFusion

I did some searching and researching. Here is a handy chart I found:

Stock fuel pressure (43.5)
135whp - 240cc
225whp - 440cc
280whp - 550cc
370whp - 720cc

According to that chart, I would have to use either 550's at a high FP, or 720's. The thing is I know I have seen guys running the 450's and getting 300 whp. What gives? If I use the BSFC calculator at RC, inputing 350 crank hp, 72# injectors @ 43.5 PSI, i get .65, which is what it should be for Turbocharged engines according to the notes. That means I have to use >720 CC injectors just to get 300whp? That doesnt seem right.

If i try to use 450cc's, I would have to run a FP of like 100psi? Wouldnt that just kill the injector? If i try to use 550's, I would have to have a FP of 70psi. Again, wouldnt this be taxing the injector? For you guys out there making ~300whp, what injectors are u using, and at what fuel pressure?

VTC_CiViC

135whp is the max for 240's!? I made 161whp on a near stock GSR on stock injectors, and guys with ITR's and such make 180whp+ on stock injectors as well... seems a little low to me.

othick

At 300whp 440's are usually maxed out at the stock fuel pressure. Mr2 turbo's come with 440's and I see people get 300whp out of those without changing injectors. 550's would be good but you can do it with 440's.

boostaholic

550's are plenty for 300whp and you don't need to run them at 70psi of fuel pressure. When i was at 300whp, 550's were at about 75-80% duty cycle and i ran them at stock base fuel press (~37psi).

DigitalFusion

it sux cause 440s can be had for like 50 bucks, 550's are gonna cost me 200+

BodyKits NW

550's. or go to the FI Classified Forum and get some 720's for like 250.00. I believe b18bturbo is selling some injectors.

COOKIEPUSS

If your going to spend the money for the 550's you might as well spend a little more for the 720's so you have can go further if you decide to turn up the boost.

quikB18B

550cc will be fine

DigitalFusion

i hear what you guys are saying, its just kinda a kick in the *** to have to go from 50 to 200+ I might look for some OEM injectors or something.. i know there are a few 550 OEM injector'ed (word?) cars out there.

danimal

how about 60 lb/hr high impedance injectors for $52 each? doesn't get much cheaper than that, wished i knew somebody who was running 'em:

http://www.mototron.com/products.htm

slixxracing

do what cookiepuss says, he's right on that. if you are deciding to get injectors why not run w/ bigger injectors so that way if you ever do decide to turn up the boost, you know you got yourself covered on the fueling. I was gonna get 550cc but i might even get something higher like 900-1000cc or something on a street car.

Muckman

iTrader: (2)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by WebGeek &raquo;</TD></TR><TR><TD CLASS="quote">
Stock fuel pressure (43.5)
135whp - 240cc
225whp - 440cc
280whp - 550cc
370whp - 720cc
</TD></TR></TABLE>

This couldnt possibly be accurate because the stock ITR uses 240cc injectors and makes 170~175 whp. Ive been told 550cc will feed up to ~350hp.

Heres a good site to calculate injector size
http://www.rceng.com/technical.htm

DigitalFusion

if u look at my first post, i was using that calculator at RC

igotyofire

isn't using to big an injector a bad thing, i notice in other post when people talk abou throwing in bigger injector they say there idle is gonna go to shiet or somthing? like b4 tunning i guess, i dont know

maxim

What are you using for tuning if you are going to use the 720cc? I imagine idling could be a bit of a struggle. If you are running Hondata, aren't there problems running 720cc or larger injectors?


Modified by maxim at 4:19 PM 11/7/2003

DigitalFusion

well i will be running chipped ECU with Crome and my own ROM burner, so idling shouldnt be a problem

shermanyang

iTrader: (1)

Xrated on here is making 400whp on his LS with only RC550 injectors. and i'm making 350whp on the same injectors as well.

DigitalFusion

at what rail pressure?

sharkcohen

As others have said, 550s would be fine. I would recommend 720s just in case you want to up the boost later.

twkdCD595

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by shermanyang &raquo;</TD></TR><TR><TD CLASS="quote">Xrated on here is making 400whp on his LS with only RC550 injectors. and i'm making 350whp on the same injectors as well.</TD></TR></TABLE>

with alot of base pressure (like 70-85psi, depending on duty cycle obviously) and the injectors at probably around 90% duty cycyle you could pull off the 400 out of the 550's.

DigitalFusion

the thing is that i dont want to have to buy an FPR, i'd like to run the stock one

Sonny

You will need to a get a true 1:1 FPR. The stock Honda one is not...and is...sometimes. It depends on what you get. I had an OEM one that didn't raise the pressure at all under boost. Two locals experienced the same with their OEM FPRs (we all had in-car gauges). I had an OEM one that did raise the pressure up to about 6 psi of boost and then it stopped. The 1:1 FPR will do the job correctly.

Sonny

DigitalFusion

damn, so i HAVE to get an FPR? Who all makes 1:1 besides AEM? Also, will the stock honda fuel pump work, or am i going to have to get a Walboro 255?

DigitalFusion

ahh, i c.. just about every FPR is one to one.. do u guys think i will need a upgraded fuel pump or will the stock one work fine with 550's ?

Sonny

To make 300 whp on 550's, you're gonna need to upgrade your pump. I've seen 240 whp on 440's at stock pressure, but the pump was starting to lose ability to keep up.

An upgraded pump is another reason why you'll need an aftermarket 1:1 FPR. The aftermarket pumps flow so much at idle, that your idle pressure will be "stuck" at about 50 psi. The return orifice is too small in the stock FPR. It cannot send fuel back to the tank fast enough.

Cleanest setup:
1) Aftermarket 1:1 FPR (like AEM, Aeromotive, etc)
2) Intank Walbro pump
3) In-car fuel pressure gauge...especially if you're gonna gamble by using the stock pump.

Sonny