Manifold pressure questions

[Artimas]

Normally aspirated aircraft-

What would be a normal manifold pressure be at idle power at sea level assuming standard conditions?

What would be a normal manifold pressure at full throttle at sea level, assuming standard conditions? Is this the same or different for all engines, and if different, what causes the difference?

 

[Clip4]

At sea level under standard conditions the MP should read:

Engine not running 29.92
Full open throttle some where around 26-28” (the induction system will effect this value a little during cruise)
Closed Throttle some where around 10-12”.

Think of the engine being a vacuum cleaner with the MP source being in the hose and the throttle plate restricting the airflow.

 

[Hank S]

Full power at sea level without turbocharging is ambient pressure minus whatever pressure losses exist in the intake system of your engine (figure an inch or so is about average).

No idea about minimum MP, because at some point below about 12", my constant speed prop operates like a fixed pitch prop and I ignore the MP needle and watch the tach instead.

 

[flyingcheesehead]

Normally aspirated aircraft-

What would be a normal manifold pressure be at idle power at sea level assuming standard conditions?

I would say probably 8-10", maybe even less. Usually at low power settings you're using the tach to set engine power, so I'm not 100% sure, but I know that in the R182, final approach was about 12" or so.

What would be a normal manifold pressure at full throttle at sea level, assuming standard conditions? Is this the same or different for all engines, and if different, what causes the difference?

It should be 29.92 minus an inch or two... Call it 28". The exception would be if the engine was de-rated with some sort of fixed restrictor plate, but I'm not sure if that is even a thing.

Where does your question come from?

 

[JohnAJohnson]

Normally aspirated aircraft-

What would be a normal manifold pressure be at idle power at sea level assuming standard conditions?

What would be a normal manifold pressure at full throttle at sea level, assuming standard conditions? Is this the same or different for all engines, and if different, what causes the difference?

JPI provides this chart in their manuals:

 

[Clip4]

JPI provides this chart in their manuals:

View attachment 71854

Except that chart has nothing to do with a running engine.

 

[JohnAJohnson]

Except that chart has nothing to do with a running engine.

Then why did you bother to list in the first line of your post above:

At sea level under standard conditions the MP should read:

Engine not running 29.92

Give me a break. I listed this as a data point to the OP, in case he wanted to check his MP gauge for accuracy before engine start. It took a little bit of effort to research, cut, save, and post, and I feel privileged to do that when I can for a fellow aviator, and if the OP wants to tell me to **** off that's fine, but as a third party, you don't get to say if my effort was insignificant.

 

[Artimas]

Thanks all.
I appreciate everyone's input here.