pressure=hp quattrorunner@lvcm.com

[JShadzi at aol.com]

Mike, you make a point, that the flow through the head is usually not a
changing factor, but my example of the pipe was more of a reference to the
turbo and the affect that the AR ratio and size of a turbo have on flow
through the engine.

Smaller turbos, like a K24 for ex, have small AR ratios and thus react
quickly at low engine speeds.  This is mostly due to the size of the AR
causing gas velocity to quickly rise in the turbo and thus spinning the exh
turbine more quicly.  Velocity is high, though, because the K24 has a very
small area in the opening in the throat or where the AR ratio are of the exh
side.  At the end of the scroll, the entire output of the engine is being
forced through about a 1/2" diameter hole in a K24.  Now, imagine the effect
of using a K27 which is about 1" in the same area- sure spool up is delayed,
but when that turbo does spool, it can flow much more air through the motor
because it is like a much bigger "pipe".

Don't forget that every turbo has a cfm rating when viewed on its flow map.
Certain turbos are used to flow certian cfm levels, just as my pipe example
illustrates.

You'd be surprised how much air can be flowed through a stock 10v head and
intake manifold if using the right turbo.

Javad

<< Hmmm, but isn't the "pipe" the same size no matter what turbo you are
 running? The pipe (the head and intake manifold) doesn't change size when
 you put a new turbo on. Just like your water pressure in pipe, if you have a
 1" pipe flowing water at 15psi, if you change the water pump (turbo) the
 pipe is still 1" and the pressure is still 15psi, so it will still flow the
 same. If you change the engine "pipe" to 2" (port the head, use a 20v head
 etc.) you WILL make more power with the same boost, because more air is
 flowing through the head at that pressure. Now of course I know that a
 larger more efficient turbo will make more power, but isn't this more a
 factor of the lower intake temps? The K26 @ 20psi is heating the air an
 enormous amount. If you had 15psi in the manifold, and going through the
 head at 115°F with a K26, vs. 15psi at 115°F going through the same head
 with another turbo (Garrett, KKK, Holset, whatever) I would bet that you
 would make the same power.
 Just a thought...probably will be shot down, but oh well :)
 Mike >>