Turbos and Blowers

[Wayne Blair]

I hope to raise some points that haven't been mentioned.

Turbos:
Sticking a paddle wheel in the exhaust path really does add complexity to
the design of the best exhaust extraction system. Thus some power is lost
due to this obstacles. 

Blowers: Positive Displacement 
Do require power to drive but the there is no obstacles in the exhaust path.

Yes the turbo is getting back some otherwise unharnessed energy.

As most of you know the end result is almost same power levels from both
systems each having an rpm range of most suitability.

All "un"-naturally aspirated engines need significant re-timing of the
valve train to optimize efficiency and hence power.

This has just been a summary so far, now for some new topics (maybe)

Blown engines ARE more efficient for the same power level !

Why ?

By example the Miller Cycle engine which is a normal 4 stroke with very
unusual valve timing (in the main very late exhaust closing) which NEEDS a
blower to run properly. These engines are about 75% the capacity of a
normally aspirated engine of similar capacity. The reason for the higher
efficiency is --- the smaller size of every thing , thus smaller surface
area to absorb heat (and be passed on to atmosphere via cooling system) and
so the extra heat is used to push the piston down there are many other
efficiencies related to size eg windage etc. This principle is similar to
STEAM engines and the good old GM 2 stroke diesel which makes good
efficient power for weight but can do little more than idle with out the
blower. An Australia designed engine also uses a similar blower dependent
design ( http://www.orbeng.com.au ). This is real and why MAZDA (i think)
are using this engine in some vehicles. In general the smaller weight and
size of the power plant allows for better handling, more aerodynamic,
faster cars. 

I hope this throws some light (from a different angle on the discussions).

wayne