In article , Jim Yanik wrote:
(Don Klipstein) wrote in
:

In article , Jim Yanik
wrote:
(Don Klipstein) wrote in
:

In article , Ernie
Willson wrote in part:

It is true that turbocharging will increase efficiency and power
output. It is absolutely not true that anything that increases
output per cubic inch will increase efficiency. Supercharging is an
example. It always increases output and decreases efficiency.

How are the above all true if turbocharging is, as explained well
by
Nate, a kind of supercharging?

- Don Klipstein )

From http://en.wikipedia.org/wiki/Turbocharging;

The objective of a turbocharger is the same as a supercharger; to
improve upon the size-to-output efficiency of an engine by solving one
of its cardinal limitations. A naturally aspirated automobile engine
uses only the downward stroke of a piston to create an area of low
pressure in order to draw air into the cylinder through the intake
valves. Because the pressure in the atmosphere is no more than 1 bar
(approximately 14.7 psi), there ultimately will be a limit to the
pressure difference across the intake valves and thus the amount of
airflow entering the combustion chamber. This ability to fill the
cylinder with air is its volumetric efficiency. Because the
turbocharger increases the pressure at the point where air is entering
the cylinder, a greater mass of air (oxygen) will be forced in as the
inlet manifold pressure increases. The additional oxygen makes it
possible to add more fuel, increasing the power and torque output of
the engine.

the "efficiency" gained is VOLUMETRIC efficiency.
"size-to-output efficiency".
meaning the motor acts like it is of much larger displacement.

turbocharging uses the wasted energy of the hot exhaust to compress
the intake charge,while supercharging is a parasitic drag all the
time.

Adding a mechanical load to the exhaust flow would increase the
pressure
in the exhaust manifold. That means work done by the pistons other
than turning the crankshaft. I hear even about so much as catalytic
converters decreasing fuel economy by adding impedance to the exhaust
flow.

Agreed,but the mechanical load from a turbo is small compared to that of a
supercharger(and HOT exhaust gas still contains a lot of energy).

I will agree to "minimal" or similarly small detriment to efficiency
with a turbocharger and much more significant detriment to efficiency with
a supercharger powered from the crankshaft.
I maintain disagreement that a turbocharger improves efficiency, other
than fuel economy improvement achieved by allowing a smaller engine.

I don't believe the Wiki article was considering catalytics, which also
are a exhaust restriction. One might have to resize their catalytic for a
high boost turbo modification, or settle for less than maximum potential
power gains.

The Wiki article does say that efficiency is better with a turbocharger
than with a supercharger. However, I still expect both to reduce
engine efficiency.

One item from the Wiki article, under "Advantages":

"Fuel Economy. Although adding a turbocharger itself does not save
fuel, it will allow a vehicle to use a smaller engine while achieving
power levels of a much larger engine, while attaining near normal fuel
economy while off boost/cruising. This is because without boost, less
fuel is used to create a proper air/fuel ratio."

- Don Klipstein )

I think we agree, then.

Maybe we majority do on turbocharging and related engine efficiency
matters!

Best Regards,

- Don Klipstein )