Miller Cycle

[Joeri de Haas]

Hi paul,

I think you mis-understood the principle. Miller cycle tries to have a
relativly smaller compression ratio and a larger expansion ratio. Therefore
Mazda closes the inlet valve very late which allows air to be pushed back
from the cylinder into the inlet manifold, which in fact shortens the
compression stroke. This allows you to run a higher volumetric compression
ratio which increases thermal efficiency during the expansion.

The downside is that your volumetric efficiency drops enormously. Therefore
you have to boost your inlet pressure to keep an acceptable power output.

Hope this clarifies what you have seen.


Kind regards


Joeri de Haas

>
>I attended the LA auto show, and was suprised to find
>that Mazda has been selling a Miller Cycle supercharged
>V-6 in their Milenia for three years.  I had not even
>heard of the Miller Cycle previously.  The system delays
>intake valve closure timing, to provide backpressure to
>a supercharger.  This then appears to provide a higher
>intake pressure, and more efficient intercooler operation.
>Higher pressure, higher temp, higher heat transfer = better
>volumetric efficiency for the motor.  Have I got it right?
>
>I was also wondering if grinding cams to give a miller 
>cycle is an option for modifying cars to run superchargers,
>as it has the effect of reducing the compression ratio,
>so says Mazda.  They claim the equivolent of 8.0:1.
>Seems easier than changing pistons!
>
>paul timmerman
>