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Old 06-23-2000, 01:21 PM   #1
SCRAPPYDO
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Member#: 873
Join Date: Feb 2000
Chapter/Region: TXIC
Location: Just outside of Houston TX
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2013 F150 King Ranch
Datsun 71 240Z & 68 2000

Cool

Actualy its the opposite.

When the gas cools down it gets more dense and slows down. The slower a liquid flows through a pipe the higher the pressure. Remember when you are washing your car and you stand on the water hose. When you squeeze the handle and the water is flowing quickly you will compress the hose. When you let off the handle the hose will fill with water and you will be picked up by the hose.

Slower moving fluids can apply a greater pressure to the walls of the pipe/hose. So if the exhaust gasses cool and slow down, they effectively can 'block up' the hotter faster moving gasses.

One of the reason that subaru puts so many darn heat sheilds around our stock exhaust is not only to keep it off our feet, but to keep the heat in the exhaust pipes, allowing the gas to remain hotter longer, and thus moving faster.

I might try leaving my 2.25" Stromung midpipe on and finding a low restriction muffler with a 2" or 1 7/8" connecting pipe. Just for kicks and see what I get.

Hope that helps JasonY

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stephen
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Old 06-23-2000, 05:30 PM   #2
Keiho
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Can't you just wrap the whole exhaust system with heatwrap? That would keep the gases hot throughout the system would it not?
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Old 06-23-2000, 08:35 PM   #3
SCRAPPYDO
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Datsun 71 240Z & 68 2000

Cool

sure you could do that.. or send the entire exhaust to JetHot and get it performance coated.. either way, but nothing will keep the gas from slowing down. Heat will help but you cant keep it from cooling down. I would be interested in doing some simple thermo on this.. be right back on this one..haha...

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Old 06-24-2000, 12:35 AM   #4
SCRAPPYDO
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Member#: 873
Join Date: Feb 2000
Chapter/Region: TXIC
Location: Just outside of Houston TX
Vehicle:
2013 F150 King Ranch
Datsun 71 240Z & 68 2000

Cool exhausting idea....

Its no secret that when fluids passing through a narrow pipe flow faster than the same amount of fluids flowing though a big pipe. Basic fluid dynamics.

An old hot rod trick was too start the exhaust with a three inch diameter pipe off the header collector. At this point the gasses were hot and were flowing quickly. As the gasses cool they take up less volume and slow down.

What we used to do was to gradually decrease the size of the pipes going through the exhaust system. By reducing the diameter of the exhaust pipes, the velocity is kept high and and gasses were expelled more efficiently.

Just a thought...

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Old 06-24-2000, 12:45 AM   #5
jasony
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You're probably right, but I wonder: if the pipe is the same diameter all the way, doesn't that mean that the cooler end will have lower pressure, and effectively help suck the higher pressure, hot end out?

I might be wrong, but if you can give some more explanation, I'd like to read it...
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