SR 370cc Injectors

[Tyler Durdan]

How much boost are the sr 370cc injectors capable of handling without running lean?  This is with a Garrett T3/T4 .63 ar housing, walbro fuel pump, and the appropriate afc.  I want to know whether these injectors will be capable of holding 10 psi without any worries of running lean.  Thanks in advance for the help, and time is of the essence.

Mark

[stil bil]

i am not sure what hp levels 10 psi on that turbo will produce, but as long as you dont go over 270HP then you are ok.  I believe that 270 is right around 95% of the duty cycle for the 370's.

hope this helps

[s13zilvia]

1 bar or 14.5 psi, is all they will handle. I would only go up to about .8 bar on a regular bases w/ out bigger injectors.

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (s13zilvia @ Nov. 25 2002,03:15)</td></tr><tr><td id="QUOTE">1 bar or 14.5 psi, is all they will handle. I would only go up to about .8 bar on a regular bases w/ out bigger injectors.</td></tr></table><span id='postcolor'>
PSI has nothing to do with it!!! That T3/T4 is going to be pushing soooooo many more CFMs than the T25 it's replacing. You will probably max out those injectors at 8-10 psi with that turbo. You really should run 550s/Z32 MAFS/ECU upgrade with that setup. If not, run low boost and see if you can get an adjustable FPR to raise static pressure a bit. But that's the jenky way to do it.

To recap: PSI has NOTHING to do with AIRFLOW (cfm)!!! They are proportionally related in reading a compressor map, but they are not the same thing in terms of power. 15 psi at 220 cfm is MUCH less power than 10 psi at 450 cfm. It's just a reading of pressure inside your intake piping...much easier to monitor than cfms. But the cfms of your turbo is what's actually making power (since that is actually how much air can flow out of the turbo)...and the reason that bigger turbos don't run out of steam (or lose PSI) up high.

Got it?

Eric

[Tyler Durdan]

Thanks Eric....gonna pass up on the sr injectors than, and go for some 550cc or something similiar.

Does anyone know a good site that shows, and/or manipulate compressor maps for different turbos?

Mark

[Jeff240sx]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Tyler Durdan @ Nov. 25 2002,3:41)</td></tr><tr><td id="QUOTE">Thanks Eric....gonna pass up on the sr injectors than, and go for some 550cc or something similiar.

Does anyone know a good site that shows, and/or manipulate compressor maps for different turbos?

Mark</td></tr></table><span id='postcolor'>
It's fairly complex math to do. &nbsp;Type in a search engine "how to turbo compressor map." &nbsp;Then go to turbonetics.com to get a map for the turbo itself. &nbsp;Then, go thru the mathematics a few times, and you are plotting various rpm's and VE to make sure you don't hit the surge line, or run off the map, which is out of the efficiency level.
Also, UIUC... I am pretty sure this is a KA-T in the making, or done. &nbsp;
Anyway. &nbsp;Untuned, 370's are good for up to 260, and with tuning, you could squeeze another 10 or so hp from them. &nbsp;15 psi on TY's car was 317rwhp-ish. &nbsp;I'd say that 10psi is 280-ish, and it would be better to go with larger injectors. &nbsp;Wither 480cc from the s15, or 550 (555) from Enjuku or any other SR shop.
-Jeff

[uiuc240]

ahh, yes, you are correct Jeff. &nbsp;i didn't do any math on the numbers, remember. &nbsp;i was just suggesting that the 370s would be quickly surpassed by a decent T3/T4 (can't remember TY's specs). &nbsp;anyway, yeah.

Eric

[Tyler Durdan]

Alright guys...need to know what injectors would be compatible with this:

At 10 psi, I will have 318.9 cfm (actual inlet cfm). &nbsp;How can I relate what size injector I need with the cfm number?

[Jeff240sx]

No.. you really can't. &nbsp;Fuel requirements are based on horsepower numbers. &nbsp;I think the CFM sizing was just to say that boost wouldn't determine the fuel requirement, becuase 20psi on a t25 is not going to net any more power than at 14psi, where it craps out, so it wouldn't need any more fuel.
It is really late, and if my math is bad, I'll fix it tomorrow.
Fuel Requirements:
Injector Size in cc / 10.5 to get lbs/hr.
Multiply by 4 (number of injectors)
Divide by BSFC (.6 for not tuned at all, .5 for some degree of tuning, and .4 if you are tuned extremely well.)
That should net you the horsepower that the injectors can handle.
-Jeff

[uiuc240]

I've been looking for a formula to relate CFM to HP, but came up with nothing. &nbsp;Let's see if we can approximate things based on the amount of air getting in to your motor. &nbsp;If there is 320 cubic feet of air per minute getting in to your motor, how much fuel will you need? &nbsp;

Well, first, we know that stoichiometric fuel ratio is 14.7:1...14.7 lbs of air for 1 lb of fuel. &nbsp;So, how many lbs of air will be entering your motor in one HOUR at 320 cubic feet per minute?

a cubic foot of air weighs 0.07 pounds

so in one minute we have 320*.07 = 22.4 lbs of air entering the motor. &nbsp;meaning that we need a minimum of (22.4/14.7) = 1.523 lbs of fuel (for all 4 injectors). &nbsp;
So divide that by 4 = .381 lbs per injector per minute. &nbsp;
Multiply that by 60 = 22.857 lbs/hr.
Multiply that by 10.5 = 240cc

However, this is for 14.7:1 ratio. &nbsp;That's not so good.

Let's refigure for 12:1 ratio.

22.4/12 = 1.867
1.867/4 = 0.46667
0.46667*60 = 28 lbs/hr
28*10.5 = 294cc

So, looks to me like you need the 370s.

Oh, and at 294cc (28lbs/hr) you'll be making this much HP:

(28*4)/.5 = 224 hp

How's that?

Eric

[Jeff240sx]

I dunno what to say man. &nbsp;The math is flawless, but I refuse to believe that he will only be making 224hp at 10psi on a KA-T with a t3/4.
I am making 195rwhp (calculated) at 4.35psi with the same turbo. &nbsp;But mine is a little more restrictive, because I put smaller housings on for spool-up time while I boost low. &nbsp;I don't know. &nbsp;But awesome deriving of a formula.
-Jeff

[Tyler Durdan]

Thanks eric.

I am gonna go with the 370cc and probably stay around 6-7psi till I get to a dyno. &nbsp;Thanks for all the help...we should archive some of these formulas for other people with similiar questions.

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Jeff240sx @ Nov. 26 2002,12:55)</td></tr><tr><td id="QUOTE">I dunno what to say man. The math is flawless, but I refuse to believe that he will only be making 224hp at 10psi on a KA-T with a t3/4.
I am making 195rwhp (calculated) at 4.35psi with the same turbo. But mine is a little more restrictive, because I put smaller housings on for spool-up time while I boost low. I don't know. But awesome deriving of a formula.
-Jeff</td></tr></table><span id='postcolor'>
Yeah, I know. &nbsp;Seemed low to me too. &nbsp;With a BSFC of .4, the number shoots up to 280hp. &nbsp; <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>

Do you have a map for this turbo? &nbsp;I'm wondering if this is the right CFM for a 1.68 pressure ratio.... (no offense Mr. Durdan...please don't Fight Club me &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=''> )

Eric

[Tyler Durdan]

No offense taken...I don't have a compressor map for it, I was just doing the formulas last night real late, and was questioning how correct I was. &nbsp;I'm gonna be going over it later again after I get off work. &nbsp;

Here are the turbo specs if you can find a map, or wanna run the numbers yourself <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'>

T3/T04B...60 trim compressor housing 50 wheel, stage III exhaust wheel with .63 ar housing.

Also, I was just talking to a local shop, and they told me the 90-96 300zx n/a using the same 370cc injectors. &nbsp;Anyone else heard of this?

[uiuc240]

well, i found some new turbo sizing info....hmmm....neat.

wow

And Turbonetics' site is down so I can't look at their neato maps.

Sheet.

Eric