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Old 04-17-2010, 08:58 PM   #61
94cobra69ss39694cobra69ss396 is offline
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Originally Posted by BRUTAL64 View Post
Need I remind you guys it is NOT backpressure
Actually it is backpressure. He has 3 psi of positive pressure in the exhaust before the cat.
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Old 04-17-2010, 11:21 PM   #62
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Originally Posted by 94cobra69ss396 View Post
Actually it is backpressure. He has 3 psi of positive pressure in the exhaust before the cat.
Out of curiosity, what's the actual name of the gauge?
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Old 04-20-2010, 03:26 PM   #63
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Originally Posted by 94cobra69ss396 View Post
Actually it is backpressure. He has 3 psi of positive pressure in the exhaust before the cat.
no it isn't---but...........................
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Old 04-20-2010, 03:49 PM   #64
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Originally Posted by BRUTAL64 View Post
no it isn't---but...........................
What would you call it?

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Originally Posted by Vettezuki View Post
Out of curiosity, what's the actual name of the gauge?
I don't remember the make, maybe Phil will chime in but here is a picture of it that I took when testing my Suburban.


Last edited by 94cobra69ss396 : 04-21-2010 at 10:49 AM.
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Old 04-20-2010, 04:04 PM   #65
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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.
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Old 04-20-2010, 04:26 PM   #66
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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.
Back pressure would be any pressure developed behind the retriction.
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Old 04-20-2010, 05:14 PM   #67
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Quote:
Originally Posted by BRUTAL64 View Post
no it isn't---but...........................
definition for "back pressure"

Back pressure usually refers to the pressure exerted on a moving fluid by obstructions or tight bends in the confinement vessel along which it is moving, such as piping or air vents, against its direction of flow. For example, an automotive exhaust muffler with a particularly high number of twists, bends, turns and right angles could be described as having particularly high back pressure [1]. Back pressure, in the exhaust sense of the term, of a four-stroke engine is usually termed as being a "bad thing" for performance; however, in the interest of reducing exhaust sound to levels allowable by public noise ordinances, back pressure can be regulated using systems from simple butterfly valves to fully computer controlled units sensing pressure in the exhaust pipe itself.

In a two-stroke engine however, a certain amount of exhaust backpressure is needed to prevent unburned fuel/air mixture passing right through the cylinders into the exhaust.

Google back pressure guage and get a thousand hits on actual test tools, google "resistance to flow" and check out some hypodermic needles. Try to find a dictionary defintion for "resistance to flow". We already had this conversation. "Resistance to flow" is the cause of the "back pressure". If the exhaust has a restriction or excessive bending that resistance will cause "back pressure" Quit being so fucking stuborn and come up with hard facts or just admit your wrong. I guess if you can't do either then just keep thinking what ever makes you feel special at the end of the day.
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Old 04-20-2010, 05:37 PM   #68
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Originally Posted by 94cobra69ss396 View Post
Back pressure would be any pressure developed behind the retriction.
Correct! Go home and turn on your garden hose for ten minutes with the nozzle tip closed, shut off the hose valve and try to take the hose off of the valve. I don't think it is "resistance to flow" that hits you in the face. I am pretty sure it is pressure. The nozzle tip creates a "resistance to flow" which causes a measurable back-up of pressure in the hose.

Have you ever seen an EGR valve called a "resistance to flow" EGR valve? NO, but they do make a positive "back pressure" EGR valve that works off of exhaust "back pressure". Toyota used to use alot of exhaust "back pressure" transducers on their EGR systems. AH! but what do they know.
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Old 04-20-2010, 06:02 PM   #69
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Quote:
Originally Posted by enkeivette View Post
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.
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.
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Old 04-20-2010, 06:04 PM   #70
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Quote:
Originally Posted by Throttle Crazy View Post
. . .The nozzle tip creates a "resistance to flow" which causes a measurable back-up of pressure in the hose. .
This is basically how I think of it.
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