2.5" exhaust

[howdy]

Header wrap and water do not play well together. Even worse if you live in an area where they salt the roads.

[ike84]

Originally Posted by howdy

Header wrap and water do not play well together. Even worse if you live in an area where they salt the roads.

Is that because they trap moisture against the pipe? I anticipated this, that's why I painted everything. Or does it wear down the wrap? I don't drive much in the rain but it will definitely happen at some point. No salt though, that's what the truck is for.

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[rfuerst911sc]

I like what you have done except the no muffler ........ that is going to be loud . Report back after you have driven it a while .

[ike84]

Originally Posted by rfuerst911sc

I like what you have done except the no muffler ........ that is going to be loud . Report back after you have driven it a while .

Will do. Ive gotta check alignment and push 996 row tune on it before I can start running her around but I will keep the post updated.

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[911monty]

While you ultimately wanted to reduce back pressure by using the 2 X 2.5" adapter that actually will increase pressure. Expanding the diameter reduces velocity of the gas, reduce velocity increase pressure. Just my .02.

[ike84]

Originally Posted by 911monty

While you ultimately wanted to reduce back pressure by using the 2 X 2.5" adapter that actually will increase pressure. Expanding the diameter reduces velocity of the gas, reduce velocity increase pressure. Just my .02.

No way dude, I used a level 5 hex to actually cause the gravitational pull of the crankshaft to accelerate flow at the level of the expansion...

Joking aside, I'm not sure I follow you there. Bernoulli's principle certainly dictates pressure inversely proportional to flow velocity over a surface, but that is not the same as pressure within a cylinder. I don't disagree with the fact that this will slow gas velocity at the expansion, and a decrease in flow velocity will certainly change flow dynamics, especially at the boundary layer (between turbulent and laminar flow). But, minimizing heat loss through the system (hence the wrap) should mitigate this and maintain the desired pressure gradient per the ideal gas law (PV= nrt, keep the nrt equal and P and V move in opposite directions) and Pousielle's law (restriction of flow through a tube is inversely proportional to the the 4th power of radius)

If your statement is correct - i.e. change in pressure is directly proportional to the cross sectional area of flow, this would mean that an infinitely large expansion (i.e. from an exhaust tube to the atmosphere) would create an area of infinitely large pressure. If that were the case, then I think we just turned our exhaust pipe into a rocket booster?!?

That is, unless I have completely misunderstood what you were getting at.

[911monty]

Originally Posted by ike84

No way dude, I used a level 5 hex to actually cause the gravitational pull of the crankshaft to accelerate flow at the level of the expansion...

Joking aside, I'm not sure I follow you there. Bernoulli's principle certainly dictates pressure inversely proportional to flow velocity over a surface, but that is not the same as pressure within a cylinder. I don't disagree with the fact that this will slow gas velocity at the expansion, and a decrease in flow velocity will certainly change flow dynamics, especially at the boundary layer (between turbulent and laminar flow). But, minimizing heat loss through the system (hence the wrap) should mitigate this and maintain the desired pressure gradient per the ideal gas law (PV= nrt, keep the nrt equal and P and V move in opposite directions) and Pousielle's law (restriction of flow through a tube is inversely proportional to the the 4th power of radius)

If your statement is correct - i.e. change in pressure is directly proportional to the cross sectional area of flow, this would mean that an infinitely large expansion (i.e. from an exhaust tube to the atmosphere) would create an area of infinitely large pressure. If that were the case, then I think we just turned our exhaust pipe into a rocket booster?!?

That is, unless I have completely misunderstood what you were getting at.

Wow. I like the KISS principle. Real world example, a centrifugal pump or compressor works by taking a fluid and increasing it's velocity (impeller) then routing to a volute (fancy name for wide part of the pipe) which decreases velocity and increases pressure. P&V inverse relationship. As far as temperature is concerned expanding gasses cool. The wrap otherwise is a good idea.

[911monty]

See the First Law of Thermodynamics (Law of Conservation of Energy) and Boyle's Law.

Originally Posted by ike84

No way dude, I used a level 5 hex to actually cause the gravitational pull of the crankshaft to accelerate flow at the level of the expansion...

Joking aside, I'm not sure I follow you there. Bernoulli's principle certainly dictates pressure inversely proportional to flow velocity over a surface, but that is not the same as pressure within a cylinder. Boyle's law states they are the same I don't disagree with the fact that this will slow gas velocity at the expansion, and a decrease in flow velocity will certainly change flow dynamics,(Bravo you are correct! The flow dynamic you reference is a conversion to pressure which is the point. Reference the First Law of Thermodynamics) especially at the boundary layer (between turbulent and laminar flow). But, minimizing heat loss through the system (hence the wrap) should mitigate this and maintain the desired pressure gradient per the ideal gas law (PV= nrt, keep the nrt equal and P and V move in opposite directions) and Pousielle's law (restriction of flow through a tube is inversely proportional to the the 4th power of radius)

If your statement is correct - i.e. change in pressure is directly proportional to the cross sectional area of flow, this would mean that an infinitely large expansion (i.e. from an exhaust tube to the atmosphere) would create an area of infinitely large pressure. If that were the case, then I think we just turned our exhaust pipe into a rocket booster?!?
And this is just being ridiculous according to the First law of Thermodynamics and energy Conversion which states that energy is not created or destroyed it is converted
That is, unless I have completely misunderstood what you were getting at.

[BYprodriver]

Originally Posted by 911monty

While you ultimately wanted to reduce back pressure by using the 2 X 2.5" adapter that actually will increase pressure. Expanding the diameter reduces velocity of the gas, reduce velocity increase pressure. Just my .02.

Also just a fact !

[ike84]

Originally Posted by BYprodriver

[/B]



Also just a fact !

On that note...

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