Quote Originally Posted by Timmy View Post
Good explanation Pickles! I kept scratching my head with what was being written in the other posts regarding CFM... As an example... The idea that you could push 1000 CFM @ 1 PSI vs. 1500 CFM @ 1 PSI through the same pipe, what the!?! Did someone not play with a garden hose as a kid enough to know that to obtain an increase in CFM at the same pressure would require an increase in the diameter of the garden hose!!!

For those who didn't get to play with a garden hose as a kid, here's the real formula.

cfm = area of pipe * sqrt (2*Pressure/density)

The idea that one turbo could deliver higher CFM at the same pressure, on the same engine, at the same RPM versus another turbo is just silly. That goes against the laws of physics (as previously stated by said poster named Pickles.)
No, genius air expands when it enters the cylinder head!!!! This why Roots Lobe Units are called Blowers-- because they develop very very low pressure all the time! So, since no engine runs at 100% volume metric efficiency throughout its entire rpm range-- you can squeeze in more air into the cylinders just by increasing the volume metric flow of the air reaching engine. Remember as the air expands to fill in the open space it will slightly cool. This is where Roots Lobe units really have problems because of the way they create pressure and volume they actually tend to heat the air up more at low rpm then they do at high rpm. But when it comes to volume metric efficiency across a broad RPM range the RL system is hard to beat. Now, with a more air friendly system like the Centrifugal unit Vortech uses the air at low pressures is relatively cold and dense-- the the more you add the greater air density in the cylinder head (up to a point). The point is this at .6 PSI there is a good bet that the Vortech unit can move enough air into the cylinder head to achieve a noticeable increase in the volume metric efficiency of the engine without requiring the engine to need extra manifold pressure to compress more air into the cylinder head. So basically, you might go form say 91% volume metric efficiency to 95% efficiency thus allowing you to burn more fuel creating a mere 30-40hp extra. Physics is just fine... All the fun laws of Boyle's, Charles', and the kinetic theory of heat are intact and happily loving each other.

What, I said was Manifold Pressure doesn't necessarily have a linear relationship between CFM and Boost Pressure! You can very well have two different turbos running at the same engine speed, on similar engines developing two radically different CFM outputs. Why do you think they make so many different units that fit essentially the same size displacement engines??? Is it because they just want to sell people two different turbos for no reason at all? No, it is because different sorts of performance goals require different types of units and peak CFM outputs for specific manifold pressures.

Then I proved to you people with a link to two Vortech V-2 mode Units that outwardly look identical with only minor differences in specifications that have 100CFM difference in peak output. And this translates to 50HP extra at peak performance all while maintaining a maximum boost of 17PSI. So, yeah, would like to try to stating again how wrong I am.

http://www.vortechsuperchargers.com/page.php?id=30157

http://www.vortechsuperchargers.com/page.php?id=30008



My entire point since day one is that if you look a boost graph and decide that some company is misrepresenting their claims on this data alone-- you will probably look foolish. There are just so many more factors that come into play with adding forced induction to an engine. If you don't know how the engines are setup and what goals each kit has-- then it is hard to say that one claim is preposterous because I've got Prodigy's turbo kit and it cannot do it. It might not be designed to do it. And that is just bummer for you. Personally, I think they put out boost graphs because they know most people buying kits aren't well enough versed in forced induction theory to really know what they are looking at.. So yeah you see 10PSI or 11PSI or 22PSI and think wow that is going to be so awesome in my car, truck, or jeep. And not knowing what exactly your engine is doing to start with gives you almost no way of knowing how effective that kit will be on your engine in the long run.