pressure=hp (long)

[rob hod]

       Javad has a very valid point which concerns itself with the obvious
aim of the turbo (to get more air into the cylinder), so did the previous
lister (was it Mr Bucholz?) who pointed out that its not just about pressure
(or even flow), and also that the temperature of the charge (keeping it
cool) is also important.

    The reason? Because the internal combustion engine is a heat engine. It
doesn't matter what the fuel is. Anyone wanting to increase the general
performance or efficiency or even a small aspect of an engines performance
needs to understand Carnots' 1824 Meisterwork 'Reflections on the motive
power of Fire and on Engines fitted to Develop that Power'.
The single  most important principle laid out by the work is that the
thermal efficiency of a heat engine and the amount of work that it can do
(power) both increase in direct proportion to the difference between the
temperature at the beginning of the power stroke and the temperature at the
end. Carnot of course existed in a world that only knew of steam as the fuel
but in a way this made it easier to understand the principle, because there
was no internal combustion occuring to distract people from the basic
principle. (although it is in reverse for steam)

    A fundamental implication of the theory in terms of a turbo application
is that if you increase the temperature of the charge (with a turbo) then
you *lose* heat efficiency. If by doing so you can create a bang that is
bigger that the energy needed to spin the turbo harder plus the increased
friction losses and the efficency loss created by the higher charge
temperature , then you have increased power. If not you have actually lost
power. This is where the Intercooler comes in, it is a virtually free method
of increasing heat efficiency on a charge thats been heated above ambient,
by increasing the temperature differential necessary by Carnots' principle
in two ways;
1, A cooler charge is by definition a denser mass and can support a larger
quantity of fuel (bigger bang, greater temp diff)
2, A cooler charge is a cooler charge period. - Greater efficiency even if
you don't take advantage of point 1 to release more power.

    Sorry for the length, but its an important principle to understand, Can
you tell its a sunday?

    HTH.

rob
----- Original Message ----- > Message: 9
> From: JShadzi at aol.com
> Date: Sun, 17 Feb 2002 00:55:33 EST
> Subject: Re: pressure=hp quattrorunner at lvcm.com
> To: quattrorunner at lvcm.com, quattro at audifans.com
>
> Brandon, the below is wrong because pressure is only a small part of what
> happens in a turbo engine.  Its like saying that in a NA engine that revs
to
> 6000rpm that if you could only remove the revlimiter and rev it to 7000rpm
it
> would make that much more power.  A turbo can create pressure, and an
engine
> can rev higher, but making real power (getting more air through the motor)
is
> due to much more than single variables like those.
>
 <   Snippage>

> > Javad
>
> << Tell me, am I wrong in assuming that if the intake manifold experiences
> 15psi in one MC engine that uses stock EM and Turbo, and another more
> modified MC engine also sees the same pressure at the intake ports, it's
> still 15 pounds going into the combustion chamber? After all, if the
engines
> still have the same set up at that point, (combustion chamber) 15lbs is
> 15lbs. Am I right? I realize that a better turbo and larger more efficient
> manifolds and runners will net you more flow and thus more potential, but
> will one engine make more power than the other without internal mods? I
need
> help understanding this if I am wrong. Thanks for the help.
>  quattrorunner at lvcm.com
>  Brandon Adams >>
>