[Throttle Crazy]

Just in case you needed more!
http://<a href="http://www.thefreedi...k pressure</a>

http://<a href="http://medical-dicti...k pressure</a>

back pressure
n.
Pressure exerted upstream in the circulation as a result of obstruction to forward flow, as when congestion in the pulmonary circulation results from failure of the left ventricle.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

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back pressure
Etymology: AS, baec + L, premere, to press
pressure that builds in a vessel or a cavity as fluid accumulates. The pressure increases and extends backward if the normal mechanism for egress or passage of the fluid is not restored.
Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.

back pressure
n
1. (Engineering / Mechanical Engineering) Engineering
a. the pressure that opposes the motion of a piston on its exhaust stroke in an internal-combustion engine
b. the exhaust pressure in external combustion engines
2. (Medicine / Pathology) Med the local pressure that builds up when fluid flow is obstructed in the cardiovascular or urinary systems
Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003

[enkeivette]

Originally Posted by Throttle Crazy

Where do you think the pressure is trying to go when the exhaust valves open. I have seen exhaust systems so plugged the engine would not stay running because the exhaust was backing up to the intake manifold and the engine could not create vaccum. I would say that is pushing up the exhaust.

I would agree with you that back pressure has multiple definitions and that it can be either upward flow, or a restriction. I was just explaining what I thought Glenn's position was.

When you create pressue, it is going to try to escape in all directions favoring the path of least resistance. So when you press your lips on a piece of glass and blow, the glass isn't pushing air into your mouth, but, pressure is trying to move back into your mouth.


So yeah, I would call it back pressure.

[BRUTAL64]

Originally Posted by enkeivette

I think Glenn's thing is, back pressure would be actual pressure pushing up the exhaust. While you're describing resistance to flow, which is pressure resulting from resistance. Not pressure resulting from some other source.

To develop: the pressure you're measuring is coming from the exhaust gas, while back pressure is not.

perfect!!!!!!!

[Throttle Crazy]

Originally Posted by enkeivette

I think Glenn's thing is, back pressure would be actual pressure pushing up the exhaust. While you're describing resistance to flow, which is pressure resulting from resistance. Not pressure resulting from some other source.

To develop: the pressure you're measuring is coming from the exhaust gas, while back pressure is not.

If it was pressure traveling directly against the exhaust from another source it would be by definition an opposing pressure not a back pressure. One pressure would not need the other to exist.
Main Entry: op·pose
Pronunciation: \ə-ˈpōz\
Function: transitive verb
Inflected Form(s): op·posed; op·pos·ing
Etymology: French opposer, from Latin opponere (perfect indicative opposui), from ob- against + ponere to place — more at ob-, position
Date: 1579
1 : to place over against something so as to provide resistance, counterbalance, or contrast
2 : to place opposite or against something
3 : to offer resistance.

[BRUTAL64]

Originally Posted by Throttle Crazy

If it was pressure traveling directly against the exhaust from another source it would be by definition an opposing pressure not a back pressure. One pressure would not need the other to exist.
Main Entry: op·pose
Pronunciation: ə-ˈpōz
Function: transitive verb
Inflected Form(s): op·posed; op·pos·ing
Etymology: French opposer, from Latin opponere (perfect indicative opposui), from ob- against + ponere to place — more at ob-, position
Date: 1579
1 : to place over against something so as to provide resistance, counterbalance, or contrast
2 : to place opposite or against something
3 : to offer resistance.

What do the French know?

[94cobra69ss396]

Originally Posted by BRUTAL64

What do the French know?

So you still haven't said what you would call it. It is not just a resistance to flow because a resistance to flow wouldn't necessarily create back pressure. A 90° bend in the exhaust pipe would be a resistance to flow but may not create back pressure.

[enkeivette]

Originally Posted by Throttle Crazy

If it was pressure traveling directly against the exhaust from another source it would be by definition an opposing pressure not a back pressure. One pressure would not need the other to exist.
Main Entry: op·pose
Pronunciation: ə-ˈpōz
Function: transitive verb
Inflected Form(s): op·posed; op·pos·ing
Etymology: French opposer, from Latin opponere (perfect indicative opposui), from ob- against + ponere to place — more at ob-, position
Date: 1579
1 : to place over against something so as to provide resistance, counterbalance, or contrast
2 : to place opposite or against something
3 : to offer resistance.

When did I ever say "from another source?"

Originally Posted by enkeivette

I would agree with you that back pressure has multiple definitions and that it can be either upward flow, or a restriction. I was just explaining what I thought Glenn's position was.

When you create pressue, it is going to try to escape in all directions favoring the path of least resistance. So when you press your lips on a piece of glass and blow, the glass isn't pushing air into your mouth, but, pressure is trying to move back into your mouth.


So yeah, I would call it back pressure.

Originally Posted by Throttle Crazy

back pressure
n.
Pressure exerted upstream in the circulation as a result of obstruction to forward flow, as when congestion in the pulmonary circulation results from failure of the left ventricle.

Your definition, back pressure - upward flow.

Think about my example. When you blow against glass, there is pressure being exerted into your mouth. Obviously, not from another source. But "pressure traveling directly against" your mouth? Yes.

[enkeivette]

Originally Posted by enkeivette

I think Glenn's thing is, back pressure would be actual pressure pushing up the exhaust. While you're describing resistance to flow, which is pressure resulting from resistance. Not pressure resulting from some other source.

To develop: the pressure you're measuring is coming from the exhaust gas, while back pressure is not.

If you're referring to my first post, once again, I was explaining what I believed Glenn's stance was. Not my own.

[Throttle Crazy]

Originally Posted by enkeivette

If you're referring to my first post, once again, I was explaining what I believed Glenn's stance was. Not my own.

I know, I understand you get what I am saying and agree. That last post was directed more toward Glens last comment (perfect!)of that same post. sorry I should have just quoted his post, but then yours would not have been there.

[enkeivette]

Oh, sorry to be so defensive. I'm in final taking argumentative dick mode right now. More so than normal.

You know what's really interesting, in the loud speaker world, when you hit the resonant frequency of a port, it will actually push air out as the speaker tries to suck air in, and it will suck air in as the speaker tries to push air out.

I wonder if this happens with exhaust gas when the resonant frequency of the pipe is hit?!