TomQ

Hello,
I was told by some tunner that I will benefit from installing bigger injectors (SVO 30lbs) with my TR 224/224 cam and FLP LTs, is it really true?
Please advise, share
Thanks!

soundengineer

iTrader: (16)

only if your injectors are pulling 80% duty..... Use A-Tap or EFI to check it...If you're close...put in bigger.

TomQ

understood
will do and see
Thanks

Team ZR-1

As I mentioned and also replied here :

https://ls1tech.com/threads/showflat...=7&fpart=1

The simple math would tell you if you needed larger injectors for best overall performance, plus tune out any knock and low timing issues.

TomQ

Does anyone know part# for 30lbs injectors?

TooManyIDs

M9593B302

http://www.thefordsource.com/store/m...rts/fuel_3.htm

94form2000z

iTrader: (10)

Awesome thanks.

Cal

iTrader: (1)

TomQ, with your setup the stock injectors should be fine.

NoGo

iTrader: (2)

I agree with CAL. The stock injectors for that setup should be more than enough.

Team ZR-1

The stock injectors will not be enough,
With Ca smog gas issues, hilly roads we have, the wrong way to solve that is to reduce timing using stock injectors when with the larger injectors knock and 91 octane issues can be solved and still maintain 28 degrees at WOT,
I say if the math cannot be done then get the PCM scanner on and red line to rev limiter and hold high engine load, now what is the pulse width and duty cycle.

Now put cruise control on at 65 MPH and have it go up the hills we have, now see what the knock and duty cycle look like with stock injectors.

bae_98Z

I just want to make sure my math is correct...

I want injectors to support 450rwhp.

450rwhp / .85 = 529.41fwhp
529.41hp / .80 (80% duty cycle) = 661.76hp
661.76hp / 8 = 82.72 hp / cyl
82.72 / 2.04 = 40.55 lbs

So I need 40.55 lbs injectors, right? Also, if there are 38 lbs and 42 lbs, I would assume the 42 lbs would be better for 450rwhp.

Thanks,
Kyung

NoGo

iTrader: (2)

I use to be a religious supporter of the injector math, reported duty cycle, yadda yadda.

I changed my mind after I starting seeing big cube after big cube car on stock 28 lb injectors go WOT just fine.
There is something missing in the inejctor pulsewidth that we are all using. I have seen on many cars the stock injectors still provide adequate fueling up to 120% duty cycle.

I use to size and scale injectors strictly by the math. I don't anymore after I found out that I was just advising poeople to purchase larger injectors than what they really needed (proven at the track and at the dyno)

Just my .02

Team ZR-1

You also have to consider the type of engine load you intend to do as the norm.
If you were only doing street driving seldom seeing high revs then the SVO 30s would be OK.

But to show as an example here is a car I am working on now :



For one you notice the injector was over 99% duty cycle by 6500 RPMs.
now if the rev limiter had been left at the 6,000 RPM as a base C5 then the problem would not be as much of a factor.

The injector flow was already over 80% by 5,000 RPMs and the knock engine had was above that.
You notice this testrun was done real world on the street ( to assure almost all trims cells were used) and at MAX engine load the engine was getting 50 lbs/min airflow, clearly a stock injector would be wacked out with that amount of air.
Notice the HP and torque.

Now consider: this is with SVO 30 injectors, so surely stock injectors would not be suited at all for this type of engine load and in this case if these types of engine loads is common to how the guy drives this C5 ( he is already on the 2nd set of tires with 15,000 miles on it) then best path would be the G.M 42 lb injectors.

This allows normal idle, part throttle etc with no loss of fuel mileage but when the hammer is dropped the injectors will not fail behind the constant engine load and allows to deal with smog gas and knock issues.

Once you get over like SVO 30 flows the costs of injectors can double if they are 38 or 42 are about the same price so your choice then is which has a longer write off use as to the future mods if they would require even more flow and install injectors that have that reserve flow ability.

BTW, this C5 is a 02 Z06 with a stock engine and only injectors, better aircleaner getting all air directly from the outside and a catback exhaust (no headers),
so my point has been with the right size injector the tuning window is much wider to meet the goals for if the stock injectors were used (as we tested) the performance numbers were quite lower.

If GM could have gotten the same performance values as shown here with stock injectors they would have done so, thus there is value in using an injector that allows a layered PCM tune to make use of the increased fuel flow.

ChrisB

For the formula to be completely accurate we would need a real BSFC, the actual scaling for rwhp to fwhp (unless you are looking at fwhp numbers).

There is also the question of RPM - at 3000 rpm you can flow twice as much fuel as you can at 6000 - so a larger engine that makes it's power at a lower RPM can many times get by with the same/smaller injectors than a higher RPM screamer.


That said, injectors are pretty cheap and they certainly won't hurt. I would first get a scan tool/scanning software. Look at your injector duty cycles - if you are much over 90 percent (or if you run sustained high duty cycles - silverstate, etc.) then go ahead and get some larger injectors. If you aren't high though then don't worry about it.

robertbartsch

I'm running rich on a H/C car at WOT with stock injectors...

I assume this means that my injectors are OK, right?

bae_98Z

Great information.

I currently run 21ms at 5800RPM, which I believe is over 100% duty cycle.

Another point. I really need 40.55lbs at 58psi, which means I would really need 35.1lbs at 43.5psi injectors, right (according to smokemup.com)?

Thanks again,
Kyung

Team ZR-1

Running the injectors static are not a positive, this requires the injector's internal coil to be on most of the time and generating more heat, plus that is additional current load on the PCM hardware drivers for the injectors control.
Most fuel deposits that form in an injector are due to hotter internal injector temps.

Not only does the bit larger injector remove those loads but also allows via tuning to where ALL "ON TPS" fuel trim cells to be well within the operating window of the STFTs and far less clock spend on LTFTs function.
We are not talking about a hugh difference in flow for even using a larger injector with tuning the pulse width is still 3 mSec or less and only when the engine demand requires it would there be more volume flow over what stock was and a bit larger injector would far lessen the fuel trims going way lean and then PCM having to work over time to bring the lean LTFTs back down.

Using a larger injector also gives better MPG, since the injectors (properly tuned) are holding LTFTs always to around zero there is less fuel spent over a stock injector that falls behind causing lean trims and then PCM commanding more fuel to reduce trim values.

GM does not use the 42 lb injector flow on the C5R for nothing and those engines as per the rules are not that greatly enhanced as to performance as many modded cars on the streets.

As to running rich with stock injectors, there is several things that mods cause the PCM to believe it is rich, simple placement of 02s further downstream can fool the PCM, also airflow, mods lying/fooling PCM to think there is more/less airflow then there really is.