Tony

You don't "detune" injectors. Just get them and put in the appropriate flow rate with LS1-edit.

First, it all depends on the power goals. That will give you a decent idea of what flow rate you need.

Then you need to consider the maximum RPM you want to spin the motor to.

Max RPM can drive a larger injector choice due to the shorter injection window. High RPM can drive duty cycle out the window if you have a marginal flow rate for the power.

Soooo....

How high do you want to spin it? And through what driveline are you running it?

You will need at least some 42's at higher pressure.

Details please <img src="gr_stretch.gif" border="0">

 

Sounds like you have two choices, 42 or 50.

Back from the Sy/Ty days, 50#ers has a noticably rougher idle. THis was in a 6 cyl though without the benefit of th LS1 runner and port design. The 50 lb injectors just werent as happy at the very low flow demands of idle, compared to 42s. I cant really say this will be the case on a big-stroke LS1, but it was on other cars. Shame you cant try both :-/

\chris

 

Harlan:

432ci (4.15" bore, 4.00" stroke)
Stage 3 LS6 heads
12:1 CR
Hydraulic cam in the 240-ish duration range
Max shift rpm 7K hydraulic, 7.5K solid roller
Short term goal 520 rwhp, long term 575 rwhp

That is the current plan, but may change without notice*

Tony

 

I would throw in the SVO 42# hr injectors, then scale them accordingly in the computer vs. your fuel pressure, etc.

For the price, etc. they are hard to beat, and it will be enough injector for your motor.


Chris

 

Is MTI closed or something? <img src="gr_grin.gif" border="0">

 

Bigger is better and besides its nice to know that you can have more fuel without any problems.

 

Well, generally I would say go with the smallest injector you can get away with, but in reality there are other factors like price, availability, etc. From all of those factors together I would submit the 42lb/hr svo's are the best deal.

Chris

 

What is a good price on those 42lb SVO injectors? I've never spent a dime on fuel system upgrades, so I have no ideas of what to expect.

Tony

 

Talk to Jayson...

I cant explain it, but I got a set of 30 lbers installed, and LS1Edit'd in at MTI for 60$ less than ThunderRacing just sells the injectors for...
Weird, but really cool.

I also got the heads swapped out/in for a hilariously low price. Alot of people think that some of us ride MTI's nuts, but if you knew what those of that use them know, you'd ride their nuts too.

Go see Jayson ;-)

\chris
whose car is actually NO longer at MTI <img src="graemlins/fluffy.gif" border="0" alt="[Fluffy]" />
(on its way to me, working, after 12 months)

 

I will be needing to upgrade fuel injectors for the new motor, and maybe even the fuel pump. Right now, my fuel system is completely stock and has served me well for 80K miles.

So, lets say I am shooting for 500+ rwhp NA, and might go with a solid roller and intake next year, hopefully 550+ rwhp then. What size injectors should I get? Should I opt for a larger than required injector and just detune them with LS1-EDIT, or go with something close to required duty cycle? I don't want to have to "upgrade" these again, and most likely I'll be keeping this motor under 600 rwhp for a very long time, or at least until I get bored again <img src="gr_images/icons/wink.gif" border="0">

Tony

 

[quote]Originally posted by Nine Ball:
<strong>Harlan:

432ci (4.15" bore, 4.00" stroke)
Stage 3 LS6 heads
12:1 CR
Hydraulic cam in the 240-ish duration range
Max shift rpm 7K hydraulic, 7.5K solid roller
Short term goal 520 rwhp, long term 575 rwhp

That is the current plan, but may change without notice*

Tony</strong><hr></blockquote>

OK

first off, w/ a 7.5k redline your inject window will be 16ms at that speed.

Assuming peak power is near there, or at 7k that leaves you w/ a window of just over 17ms.

So lets say you are making 550 RWHP at 7k

a reasonable drivetrain loss will put you at, lets say 625 FWHP.

Your NA so BSFC should be close to .5

625 HP at the motor will require 625*.5 = 312 lb/hr of fuel to make the power.

divide by 8, and lets say limit the duty cycle to 90%

312/8=39 lb/hr for each injector at assumed 90%

so the injector needs to be 39*1.1=42.9 lb/hr

SVO 42's at the LS1 higher base pressure will give you just under 50 lb/hr injectors.

So, the flow rate is there.

can you flow the flow at high RPM is the question.

Lets go the other way

picking 50 lb/hr as the flow rate

100% duty cycle at 7k you flow

in .017 sec you flow .017(sec)*50lb/hr/3600*8=
.0018 lb/pulse

at 7000k there are 3500 pulses per minute

so, to put all that together

.0018*3500*60=378 lb/hr

Now i'm sure that doesn't make a whole lot of sense

But, the moral is....

With SVO 42's at 7k and 100% duty cycle you theoretically can flow enough fuel for ~750 FWHP at BSFC of .5 <img src="gr_stretch.gif" border="0">

BTW, $320 is a decent price for them new, about $200 to $250 used.

Somebody check my math <img src="graemlins/fluffy.gif" border="0" alt="[Fluffy]" />

 

Thanks Harlan, you nerdy Engineer! <img src="gr_images/icons/wink.gif" border="0">

SV0 42lbs it is then.

 

I agree Tony, the SVO 42's are great and served me well past the 600RWHP mark in my former SS.

Just remember you need the fuel pumps to supply those injectors. I would look at doing a dual Walbro intank setup. <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

-Jeremy

[ March 01, 2002: Message edited by: Godspeed ]</p>

 

Doesn't hurt to spend a few extra bucks and get them flowed and calibrated. <img src="gr_stretch.gif" border="0">

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

 

[quote]Originally posted by Paulie:
<strong>Doesn't hurt to spend a few extra bucks and get them flowed and calibrated. <img src="gr_stretch.gif" border="0">

http://www.rceng.com/index.htm</strong><hr></blockquote>

I agree I bought a new set that had been flow matched for my setup.