MAP behavior question

Bob F. wrote:
Here's a question ...
When a normally aspirated engine quits while at cruise, how does the MAP
react with respect to the throttle?
Does it indicate zero?

Only in outer space. Or if the gauge is broken.

Does it indicate barometric pressure?

With an open throttle and stopped prop.

Does it pin? (Go to max)?

Why would it do that? If you are 'cruising' on the taxiway, you might
get the 29.9-30 inches reading, if it dies there.

Does it follow the Throttle (high MAP with a high throttle setting , low
when set to low throttle setting)?

Yes. except as noted above.


...and why?


Because an engine is an air pump. If the pistons are moving air, then
the air pressure can be measured by the MP gauge. The throttle will
manipulate the air pressure as the engine pumps air past it. Closed
throttle, low pressure. Open throttle, high pressure.