Manifold Pressure

[rodrop]

Ok, me again...another...need it to make more sense question. What is manifold pressure..? other then saying it is a power settting ? What does it really measure and how do you know when it is high or low? Is it related to any other pressures/ (pressure altitude?). I have been reading about manifold pressure and not alot is out there other then it saying...watch out and dont let it get too low or too high...hmmm..... Any comments or links where I can read more about it, would be appreciated. Thanks ahead of time.

[tattooed]

There is a sensor inside the manifold that measures the pressure of the fuel/air mixture...which is then indicated on you MAP gage on your console.

The amount of power produced is directly related to the air/fuel mixture being "delivered" to the combustion chamber.

When you open the throttle, more air/fuel mixture is going into the combustion chamber, and will show an increase in pressure.

 

Does that help?

 

Automotive books may have more info.

[Goldy]

check out the search area of the forum...its been asked before and I recall some pretty good explanations..

 

Good Luck, Goldy

[Witch]

Think of it as a partial vacuum in the manifold. Low pressure means that the engine is running near idle, butterfly closed, or low power. High pressure means the engine is running full boar (bore?), butterfly open, or high power. The best place is with the butterfly half-open, or half-power.

 

Simple?

 

Later

[kodoz]

running full boar (bore?)

 

 

Running full boar

 

 

 

Fool, running boar

 

[EC120AV8R]

Running full boar

 

 

 

Fool, running boar

 

 

Too friggin' funny. Nicely done.

[justfly]

Ok, me again...another...need it to make more sense question. What is manifold pressure..? other then saying it is a power settting ? What does it really measure and how do you know when it is high or low? Is it related to any other pressures/ (pressure altitude?). I have been reading about manifold pressure and not alot is out there other then it saying...watch out and dont let it get too low or too high...hmmm..... Any comments or links where I can read more about it, would be appreciated. Thanks ahead of time.

from page 5-4 of Pilot's Handbook of Aeronautical Knowledge FAA-H-8083-25:

...power output is controlled by the throttle and indicated by a manifold pressure gauge. The gauge measures the absolute pressure of the fuel/air mixture inside the intake manifold and is more correctly a measure of manifold absolute pressure (MAP). At a constant r.p.m. and altitude, the amount of power produced is directly related to the fuel/air flow being delivered to the combustion chamber. As you increase the throttle setting, more fuel and air is flowing to the engine; therefore, MAP increases. When the engine is not running, the manifold pressure gauge indicates ambient air pressure (i.e., 29.92 in. Hg). When the engine is started, the manifold pressure indication will decrease to a value less than ambient pressure (i.e., idle at 12 in. Hg). Correspondingly, engine failure or power loss is indicated on the manifold gauge as an increase in manifold pressure to a value corresponding to the ambient air pressure at the altitude where the failure occurred.

[rodrop]

Thanks for all of the responses...this definitely helps. I will do a search on the forum from some of the older stuff (Thanks Goldy--good suggestions, always an oversight). The "bore" thing... hmmm...no comment on full bore, etc

 

I thought if I read about the automotive stuff, it might help...so thats Tat, I will do that too.

 

Thanks again, to everyone

[joker]

http://helicopterforum.verticalreference.com/helicopterfor...old+pressure%5C

 

Here's a list of links which might help you.

 

All threads about manifold pressure, from back in the days...

 

 

 

In short, as a piston goes downwards, it draws air into the manifold like a pulling a syringe.

 

(The manifold is the space of the engine above the piston.)

 

This drawing (pulling action) causes a drop in pressure. The manifold pressure measures this 'SUCTION'.

 

 

 

 

Joker

 

P.S. Hello everyone!

Edited May 18, 2008 by joker

[rodrop]

http://helicopterforum.verticalreference.com/helicopterfor...old+pressure%5C

 

Here's a list of links which might help you.

 

All threads about manifold pressure, from back in the days...

 

 

 

In short, as a piston goes downwards, it draws air into the manifold like a pulling a syringe.

 

(The manifold is the space of the engine above the piston.)

 

This drawing (pulling action) causes a drop in pressure. The manifold pressure measures this 'SUCTION'.

 

 

 

 

Joker

 

P.S. Hello everyone!

 

Thanks, nice summary and good link...thank you