http://www.gnttype.org/techarea/turbo/turboflow.html
Okay guys, if you read over this website very carefully, and understand the equations, this "bigger always means more hp @ same psi" should stop.
I think we can all agree that how many pounds of air you can fit into an engine is what increases the power of an engine.
Here is the equation to determine it:
To get pounds of air:
n(lbs/min)=
P(psia) x V(cu.ft./min) x 29
....................... (10.73 x T(deg R))
Okay, if you read that article, you will find that:
The variable
P is pressure as in PSI (absolute pressure)
The variable
V is volume, as in cubic feet per minute. (this is not changeable on a given engine without increasing displacement or rpms)
The variable
T is temperature (absolute temperature)
okay, here we go:
24.7psi x 250cfm x 29 = 179075 ( 24.7 is 10 psi + 14.7, 29 is metric conversion shit)
10.73 x 550F = 5901 (10.73 is more metric conversion 550 is 90 degrees + 460 (to make it absolute))
179075/5901 = 30 lbs/min of air
A stock GSR running 10 psi of boost at the map sensor, with the air being 90 degrees F, will combust a total of 30 lbs of air per minute
If you leave the engine alone, there are only 2 variables you can control in this equation. PSI and temperature. You can control the temperature by getting a larger intercooler, and you can control PSI by getting a boost controller or a stiffer spring in the waste gate.
Using that same equation, you can find out how many lbs/min a gsr with no boost can run. That number is 18 lbs/min assuming its 90 degree air getting into the engine.
18 lbs/min vs 30 lbs/min
30/18 = 1.67 ....does that number sound familiar?
Now if you guys are still in question about the cf/m of an engine not changing, picture it this way. Pretend that I gouge out one of your eyeballs, stick my arm through your eyesocket until i can grab your brains, and then I scoop all your brains out. There's now nothing left inside your thickskull besides 5 cubic feet of air (you have a really big head). Okay, so its now established that your head holds 5 cubic feet of air. Now what I do, is I go get the biggest freaking turbo I can find, and I hook it to your eye socket. When it starts blowing, provided your head doesnt expand or explode, how many cubic feet will your head be able to hold? uhm 5 cubic feet, why would that change? So what happens to all the air that that big turbo pumped into your head? It is just compressed. Yes, a larger turbo can put more pounds of air into a given space than a smaller turbo, but it has to do so at a higher pressure.
A GSR engine can only accept...lets day 250 cf/m. Your waste gate is set at 10 psi. Your intercooler cools your air down to 90 degrees. So what if your turbo can push 750 cf/m at 10 psi. Since no more than 250 cf/m can go into the engine, the system builds up pressure. Since the system stops building pressure once it reaches 10 psi, the turbo is only running at part capacity.
on a 250 cf/m engine running 10 psi, the only difference between a 250 cf/m turbo @ 10 psi, and a 750 cf/m turbo @10psi, is lag. Lag is bad if you are looking to increase horsepower throughout your whole rpm range.
As for the relationship between cf/m and psi (assuming they are both intercooled to 90F):
30 psi on a 250 cf/m engine = 55 lbs/min
10 psi on a 750 cf/m engine = 91 lbs/min
So how do you increase the cf/m's of an engine? Increase RPMS, Bore it, Stroke it, or polish it (which doesnt actually increase displacement, but helps the other factors become more efficient)
You guys have got to remember that if a turbo is pushing the cf/m of the engine, at the waste gate's max pressure, getting a larger turbo will do nothing good for you. It will not increase the lbs/min of air going into the engine, and will not make your engine any more likely to blow up than the smaller turbo.
pissedoffsol, instead of getting the largest turbo you can find, lets do the math and figure out which turbo will push howevermany cf/m your engine moves at 10 psi. That way you reduce unnecessary lag, and increase the average horsepower of the engine.
Guys, I am sick of being called a moron. I am right. There is no doubt about that. If you need anything cleared up or explained better, please ask me, instead of telling me how stupid I am. If you want any references for those things that I am telling you about, please ask me for them, and I will do my best to get them.
As for you mwasnp, "do the math and then send me an apology" Your ignorance is not excuseable because you were sooo malicious about it. I really need to post those messages you sent me.
As for everyone else, nobody had explained the math to you yet