There are a few more things to factor in as far as if an injector is big enough to support your engine. The key things you need to know is engine size, Max. RPM, absolute pressure peak that means 14.7 plus whatever your guage reads at your max RPM. From there you need to figure out what AFR you want because obviously that is how much fuel your putting into the engine. You will also need to know how many cycles/min. your enigne turns at your max rpm. From there you can calculate CFM at different VE's. Your base should be form 100% VE. You will need to know the density of the air. From all that information with some physics equations and some simple algebra you can figure out your exact IDC at your Max. RPM telling you if your injectors are actually going to be big enough for you engine. HORSEPOWER HAS NOTHING TO DO WITH INJECTOR SIZE.

 

yes i know this, it was more or less something to get people to kick start the brain into digging more into it.

fuel have everything to do with horsepower, hence why injectors have something to do with power in general.

why do i say this? say you have a car with 450cc injectors, or 36lb injectors, whatever you want it to be. you are running x amount of power. that x amount is limited by that. you can not run a bigger dry shot of nitrous, or more boost. why? you don't have the fuel system to support it.

say you have a car running 15 psi on 36lb injectors. what happens when you jump to 18? out of fuel. injectors going static. what happens when you get 50-60 whatever you want with that. AH HA, turn the boost up, MAKE MORE POWER.

lets turn the tables. say you have a sbc based motor. heads, cam, nice built motor. you have a 500 cfm carb on it. it's killing the motor, it needs more. what happens when you stick a 750 on it. DING, more power. bigger boost/power, it requires more fuel. period.

 

your close but your still wrong. fuel is used to support proper combustion. Air is what makes more horsepower. You should realize this considering you just said add more boost or a bigger carburateur to increase power, the fuel is there only to support combustion. Whether i set my AFR to 11.5 or 12.5 with all other variables exactly the same aka. CFM through the engine, density of that air then my power will not change. The reason everybody with an LSJ puts a smaller pulley on the blower is to push more air into the engine. the more air into the engine the more cylinder pressure can be obtained hence more power.

sorry to put another post in but i just realized somethign else you wrote about having the proper size fuel system to support the power and u are correct with that because of the fact that you are putting more air into the engine or turnign more rpm's. rpm's is where like the GM stage 1 kit comes in because with the stock injectors don't have the required amount of time to put enough fuel into the engine at 7k so you are correct in saying you need a fuel system to support your power which can be easily figured out with some math but for AIR makes power not fuel. Also just FYI for anyone who cares I work at an engine shop in PA, the owner has a degree in engineering and has all the math to prove what i'm saying also I have passed through the EFI university's ACP class which also goes over engine and air physics to prove what i'm saying.

 

degree's mean nothing to me. air it self does not create power. it can however. if you are more concerned about a windmill than moving your car down the road. yes air does make power, so does fuel. you need a combustable source to make use of said air. air by itself will not ignite. when added with a fuel type source, methane, propane, nitrometh, gasoline, whatever it may be. this in itself is needed, along with a spark source. when all three of these are crammed together in a chamber about the size of the top of coke can, give or take a few cc's. what happens. explosion. then the fun begins.

when you change a pulley, heads, cams, whatever it may be, you introduce more air into a vehicle. you need more fuel. pure and simple. if fuel injectors don't make power, or aid in the internal combustion process, we not have to worry about them ever. stock would be fine. there would not be a need for the aftermarket fuel injectors ever. we could all make 1000 hp just by shoving a turbo on to a car, cranking the boost to 40 psi, and run 87 octane fuel. because hell, air makes power.

you refered to the stage 1 being just injectors. peachy great! why. because you can't make anymore power on the factory chosen injectors, so you need more fuel to make that extra power.

air. fuel. and spark. there is not a one sided issue on this.

btw, im not trying to turn this into a war between anyone. im just more or less posting this for people to get a better idea, for them to brainstorm and make them think, instead of making others think for them. i myself have been guilty of this. we all do it at some point in time.

 

dont forget adding cylinders doesnt just double hp it adds more. if you take a .5l engine that makes 65 whp and add another .5l piston you dont get 130 whp you get somewhere nearer to 200 whp. when you take a 3.8 gm motor that makes 200 hp and add 2 more cylinders you dont get 320 like the ls1 (not the same just saying you cant just add the numbers of hp per cylinder and get the overall hp)
as for fuel we need more pressure in the system to make better power with the smaller injectors or to just add more injectors to make up for the problem. why not add a boost a pump to the secondary injectors and once you get in the boost the thing dumps tons of fuel into your system. you can still have the computer read and regulate with the 4 stock placement ones

 

Everything will always be relative. Are all injectors going static @ 20 Ms ? No. Are all injectors going static @ 20Ms and @ 6000 RPM ? Yes. IPW only doesn't tell you when the injectors turns static.

For the HP calculation, there is some VERY important variables that are needed in the formula to get a precise horsepower estimation. First there is the BSFC (Brake Specific Fuel Consumption). Secondly one of the most important is the differential pressure between the fuel rail and the manifold.

As a pure example, a Stage 2 Cobalt SS with a 2.8 pulley boosting 17 PSI. The differential pressure is only (58-17 = 41 PSI). How many WHP these 42# injectors will support ? Probably only 250 WHP (on a safely way and I'm not talking of IDC over than 100%).

Another example is the GMPP LSJ 300+ HP Build book. They got a set of 44# injectors installed and also a ported head and upgraded cams. They run a 2.9" pulley. The boost they got isn't mentionned, but is way less than the previous example. Guess what they supported at least 310 WHP.

And about that "wall" in HPTuners. A common error (made by several INCLUDING ME) has been to believe that it takes so much boost to get high levels of power on that car.

If you make a calculation at -80KPA vaccum (when the injectors flow the most) and a fuel rail pressure of 58 PSI, you'll see that the maximum flow injectors allowed by HPTuners is exactly 50 lb per hour. Which is way enough to support at least 350-375 WHP when boosting less than 15 PSI which is clearly a more efficient boosting range.

 

you are obviously not ready my post at all. I would suggest reading it again and then look at what you wrote. Not only did I say that more air = more horsepower but i said the fuel is there to aid in combustion. I am telling facts that if you change your AFR richer you WILL NOT make more power. Power comes from max cylinder pressure in a cylinder at a certain point in crank degrees where the rod is. You WILL NOT increase your cylinder pressure by adding more fuel to the engine. There has been studies on AFR and how they effect power and some other things and the final result was that in a controlled state they changed AFR i believe from about 12.3 to 13.3 and there was less that a 5% change in HP. anything richer than 12.3 made no gains in overall power. Anything leaner than 13.3 would start to see significant decrease in power. These are just the facts just like you I am not here to start a war but i put it out there to say that if anybody on this forum calls up any respectable engine builder and asks thems anything that we have talked about they will say exactly what I have said.

 

I think both of you are right.

 

i did read it, actually a couple times.

12.3-13.3. thats more or less for naturally aspirated gasoline engines.
i personally run 11.8 a/f in my car.

jmc,

it is safe to say that 42's will support more then 250 whp. if one were to make the motor itself more efficient instead of adding more boost. it would be a happier motor.

im making people think now, this is good. keeping adding to it


show me your theories on this idea.

 

this right here makes sooooo much sense on why gm setup stage 3 the way it did.
they werent worried about boost, they only go to a 2.99 pulley if im not mistaken. i mean why would they support a 50 dry shot if the injectors cant pump enough fuel to support it. they must have realized for this motor theres a range of "usable boost". ya you can run a 2.5 and pull tons of air but if the engine cant use it its just exhaust.

personally i think they did it because at that point its maxed. then the injectors need upgrading.

found it from jnc... "If you make a calculation at -80KPA vaccum (when the injectors flow the most) and a fuel rail pressure of 58 PSI, you'll see that the maximum flow injectors allowed by HPTuners is exactly 50 lb per hour. Which is way enough to support at least 350-375 WHP when boosting less than 15 PSI which is clearly a more efficient boosting range."

just my .02 maybe gm isnt as stupid as we think

 

that might explain why i have a higher trap than most of the 2.6" pullied cobalts on this site

 

wow...

 

42! ! ! !

 

*rubs forehead* my brain hurts now. thanks guys

 

bad drivers thats all

 

lol!

the answer is 42.

****!
i thought it was 29?


what is your take on this idea. i know you have a bit of knowledge on the lsj. willing to share the thoughts rolling are you head there?

 

ya im interested in knowing a bit more also... no to throw in anything else here but isnt heat soak the biggest problem for these engines... and doesnt that come into play with smaller pulleys and well everything else the engine is doing.

 

Area47, what all do you have done to your car? 11.8 afr seems a bit lean to me. are you running meth injection? you on 42# injectors? pulley size?

 

my a/f ratio is a secret number. but it runs happy.

42's
2.8
water injection.
pacesetter header
3 inch crush bent dp
3 inch cat back
k&n intake.

 

Area47, read this artical from GM, gmtunersource.com, scroll down to the Stage 3 artical. They mention the actual size of our injectors, with some other info.

 

i really dont see why 42pounders cant make well in he 300whp range

ok im lost all over again. tey say the 42 pound injectors flow between 55 and 60 pounds. wow i dont get the math they use

 

They are using the normal calculations. The fact is that the Stage Injectors are NOT 42lb units they are 58lb injectors. 42's can not support 300hp, only around 240, but 58lb units can. When the GM stage kits came out a year and a half ago someone stated the injectors were 42's, this was then taken as truth, but the was no proof. now in this article GM states they are infact flowing 55-60lbs/hr=58lbs.

 

42.5's being force fed 58 psi of fuel pressure will increase the amount of fuel the injector is capable of flowing. the industry standard is 43.5 as a base pressure. this is what all injectors are rated at.
i do not tend to believe any blogs i read. period. going off their 310 hp idea is a shot in the dark. people have gone over this, and people have barfed bone stock cars.

 

Guys the 42.5's will support more than 240 hp... Believe me they do!

I myself and pretty much every other car from KC is running 240 or more HP! And we have dyno sheets and logs to prove such!

Area.... man you know how to get heads rollin' man...

 

[italian accent] im gun send tony down der if they don streiten up dem heads[/accent]