Cessna TURBO CENTURION T210M 1978 Pilot Operating Handbook page 161

CESSNA
MODELT210M
SECTION 7
AIRPLANE
&
SYSTEMS DESCRIPTIONS
The turbine has the capability of producing manifold pressures in
excess of the 5 minute takeoff maximum of 36.5 inches Hg. In order not to
exceed 36.5 inches of manifold pressure, a waste gate is used so that some
of the exhaust will bypass the turbine and be vented into the tailpipe.
It can be seen from studying Steps 1 through 4 that anything that
affects the flow of induction air into the compressor or the flow of exhaust
gases into the turbine will increase or decrease the speed of the turbo-
charger. This resultant change in flow will have no effect on the engine if
the waste gate is still open because the waste gate position is changed to
hold compressor discharge pressure constant. A waste gate controller
automatically maintains maximum allowable compressor discharge
pressure any time the turbine and compressor are capable of producing
that pressure.
At high altitude, part throttle, or low RPM, the exhaust flow is not
capable of turning the turbine and compressor fast enough to maintain
maximum compressor discharge pressure, and the waste gate will close to
force all of the exhaust flow through the turbine.
When the waste gate is fully closed, any change in turbocharger speed
- will mean a change in engine operation. Thus, any increase or decrease in
turbine speed will cause an increase or decrease in manifold pressure and
fuel flow.
If
turbine speed increases, the manifold pressure increases; if the
turbine speed decreases, the manifold pressure decreases. Since the
compression ratio approaches 3 to 1 at high altitude, any change in
exhaust flow to the turbine or ram induction air pressure will be magnified
proportionally by the compression ratio and the change in flow through
the exhaust system.
MANIFOLD PRESSURE VARIATION WITH ENGINE RPM
When the waste gate is open, the turbocharged engine will react the
same as a normally aspirated engine when the engine RPM is varied. That
is, when the RPM is increased, the manifold pressure will decrease
slightly. When the engine RPM is decreased, the manifold pressure will
increase slightly.
However, when the waste gate is closed, manifold pressure variation
with engine RPM is just the opposite of the normally aspirated engine. An
increase in engine RPM will result in an increase in manifold pressure,
and a decrease in engine RPM will result in a decrease in manifold
pressure.
MANIFOLD PRESSURE VARIATION WITH ALTITUDE
At full throttle, the turbocharger has the capability of maintaining the
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