Re: S4 20v vs S2 10v

[cordeiro@adi.com (Alan Cordeiro)]

>Is not the amount of air moved purely a function of the boost pressure,
>all else being equal? In other words, if the S4 turbo can maintain the
>same boost pressure as, for example, the RS2 turbo, at a given RPM, then
>will not both turbos be moving the same amount of air? I should think
>that so long as the smaller S4 turbo can "keep up" with the required flow
>rate, ie the boost pressure does not drop below the WG setting, that the
>S4 and the RS2 turbo would be moving the same amount of air and the
>power/torque output would be equal. If this is all true, then the RS2

The engine requires AIR MASS, or QUANTITY of air, and this is a
function of ABSOLUTE PRESSURE and ABSOLUTE TEMPERATURE and
finally AIR VOLUME

Therefore, power depends on boost, the initial air pressure ( if you
are at high elevations, you can run higher boost )  and temperature o
f the fresh air charge ( hence the intercooler ).


>my understanding is that the 9.3 compression on the S4 is for
>off-boost response.. once the turbo spools up, CR is really quite a
>meaningless number, because 2 bars of boost is 2 bars of boost,
>regardless of what the geometric dimensions of the engine are.  i.e. 2
>bars in a 9.3 compression engine is equally likely to detonate as 2
>bars in a 7.8 engine, all other things being equal.. no?

NO !!
Boost pressure is at the intake manifold. The engine then FURTHER
compreses it according to the compression ratio. Therefore high boost
+ high compression => higher likelihood of detonation.

Alan Cordeiro