Straight piped...engine damage?
11-03-2008, 06:17 PM
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with a diesel, there is no pre-ignition. diesel engines run on 'pre-ignition'... fuel is injected and it starts burning. this is a compression-ignition engine, not a spark-ignition engine.
With a diesel engine if you have black smoke, there is either not enough air, or too much fuel.
With a diesel engine if you have black smoke, there is either not enough air, or too much fuel.
11-03-2008, 07:19 PM
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I personally want THE most complicated answer, Abe. Please, leave nothing out, and use correct technical terms, if you will.
11-04-2008, 06:06 AM
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with a diesel, there is no pre-ignition. diesel engines run on 'pre-ignition'... fuel is injected and it starts burning. this is a compression-ignition engine, not a spark-ignition engine.
With a diesel engine if you have black smoke, there is either not enough air, or too much fuel.
With a diesel engine if you have black smoke, there is either not enough air, or too much fuel.
11-04-2008, 06:23 AM
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People saying you need backpressure yet again 
Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure.
Gadget explains this better than anyone..
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
Check this out, airplanes fly. They do this by managing flow dynamics also known as fluid dynamics. When you increase the velocity of a fluid its pressure decreases. When this decrease in pressure is above the wing, the pressure under the wing pushes up lifting the plane into the air. When you decrease the velocity its pressure increases. When air is drawn through a venturi in a carb the pressure drops and that is what draws the gas out of the bowl and into the air stream. If you look at a venturi you would think that it is a big restriction, but it causes the pressure to drop. A venturi is basically an airplane wing in a circle.
Now with an exhaust system you want the lowest pressure you can get so the engine works less hard pushing the exhaust out. So, it is all about flow management. A small pipe will cause the flow to be faster and it travels down that pipe in pulses. The faster it goes the less the pressure is especially after the pulse wave. If you get to big of a pipe the velocity slows down and the pressure increases. So a large diameter pipe can in fact result in a higher pressure in the pipe and cause the engine to work harder to push out the exhaust and you loose torque.
Do you want a visual aid? If so, light two candles. Place them about 6? apart. Now blow between them. You will notice that the flames lean toward the air that you are blowing between the candles. This is because the pressure between the candles dropped and the higher-pressure air is rushing to move toward the low-pressure air pushing the flames over as it passes through.
Now there are always compromises. Your engine runs at different RPMs and different loads and you will want the smallest diameter pipe possible without restricting high flow at high RPM and loads. At some point a small diameter pipe will become flow restrictive and will need to be larger, but the trade off is loss of low load velocity and increased pressure and you perceive this as loss of low RPM torque. A short straight pipe is best but you have packaging problems. If you have to have bends, the bends should be a larger diameter then the straight sections because you want the flow to slow down to reduce turbulence in the bend, but this really adds huge cost to the system. Now if you really want something slick, have all your bends take on the NACA duct peanut shape for the best possible flow. Mandrel bending prevents a smaller diameter then the straight and is usually the best you get.
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
__________________
Gadget
Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure. Gadget explains this better than anyone..
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
Check this out, airplanes fly. They do this by managing flow dynamics also known as fluid dynamics. When you increase the velocity of a fluid its pressure decreases. When this decrease in pressure is above the wing, the pressure under the wing pushes up lifting the plane into the air. When you decrease the velocity its pressure increases. When air is drawn through a venturi in a carb the pressure drops and that is what draws the gas out of the bowl and into the air stream. If you look at a venturi you would think that it is a big restriction, but it causes the pressure to drop. A venturi is basically an airplane wing in a circle.
Now with an exhaust system you want the lowest pressure you can get so the engine works less hard pushing the exhaust out. So, it is all about flow management. A small pipe will cause the flow to be faster and it travels down that pipe in pulses. The faster it goes the less the pressure is especially after the pulse wave. If you get to big of a pipe the velocity slows down and the pressure increases. So a large diameter pipe can in fact result in a higher pressure in the pipe and cause the engine to work harder to push out the exhaust and you loose torque.
Do you want a visual aid? If so, light two candles. Place them about 6? apart. Now blow between them. You will notice that the flames lean toward the air that you are blowing between the candles. This is because the pressure between the candles dropped and the higher-pressure air is rushing to move toward the low-pressure air pushing the flames over as it passes through.
Now there are always compromises. Your engine runs at different RPMs and different loads and you will want the smallest diameter pipe possible without restricting high flow at high RPM and loads. At some point a small diameter pipe will become flow restrictive and will need to be larger, but the trade off is loss of low load velocity and increased pressure and you perceive this as loss of low RPM torque. A short straight pipe is best but you have packaging problems. If you have to have bends, the bends should be a larger diameter then the straight sections because you want the flow to slow down to reduce turbulence in the bend, but this really adds huge cost to the system. Now if you really want something slick, have all your bends take on the NACA duct peanut shape for the best possible flow. Mandrel bending prevents a smaller diameter then the straight and is usually the best you get.
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
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11-04-2008, 06:31 PM
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I was just trying to relate diesel engine operation to something non-diesel familiar people might understand. It's true that diesel cannot pre-ignite. Spontaneous combustion is EXACTLY what causes diesel fuel to burn in a 4-cycle (otto?) engine. But for people from a 'gasoline' background, spontaneous combustion is bad... pre-ignition, pinging, spark-knock, detonation (though technically that is the wrong term to use, but can happen in a gas engine)... should I call it deflagration?
11-04-2008, 07:10 PM
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People saying you need backpressure yet again Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure.
Gadget explains this better than anyone..
okay, here goes....
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure. Gadget explains this better than anyone..
okay, here goes....
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
we're already off to a bad start here.
Check this out, airplanes fly. They do this by managing flow dynamics also known as fluid dynamics. When you increase the velocity of a fluid its pressure decreases. When this decrease in pressure is above the wing, the pressure under the wing pushes up lifting the plane into the air. When you decrease the velocity its pressure increases. When air is drawn through a venturi in a carb the pressure drops and that is what draws the gas out of the bowl and into the air stream. If you look at a venturi you would think that it is a big restriction, but it causes the pressure to drop. A venturi is basically an airplane wing in a circle.
Someone really needs to rethink their knowledge of how planes fly. When you increase the velocity of a fluid, the pressure increases. If what was said is true, blow into an anemometer. If pressure decreases when velocity increases, air pressure should drop.
It's only when the fluid travels over a restricted / confined space that the pressure decreases within that space.
If you actually graph the pressure exerted on the wing of an airplane, there is a net-zero effect. In order to fly, the wing must exert force against something else. Now, using a wing to describe fluid motion and pressure gradients within a confined space isn't exactly the best way to do so. Matter-of-factly, it's just plain-and-simple wrong.
And a venturi is not the same thing as a wing. Show me how 'wing theory' relates to pressure gradients caused by air flow across the open end of a cylinder.
Now with an exhaust system you want the lowest pressure you can get so the engine works less hard pushing the exhaust out. So, it is all about flow management. A small pipe will cause the flow to be faster and it travels down that pipe in pulses. The faster it goes the less the pressure is especially after the pulse wave. If you get to big of a pipe the velocity slows down and the pressure increases. So a large diameter pipe can in fact result in a higher pressure in the pipe and cause the engine to work harder to push out the exhaust and you loose torque.
Do you want a visual aid? If so, light two candles. Place them about 6? apart. Now blow between them. You will notice that the flames lean toward the air that you are blowing between the candles. This is because the pressure between the candles dropped and the higher-pressure air is rushing to move toward the low-pressure air pushing the flames over as it passes through.
But when I blew through a straw, they were both drawn towards the air flow, with little sign of the turbulence seen before....
Now there are always compromises. Your engine runs at different RPMs and different loads and you will want the smallest diameter pipe possible without restricting high flow at high RPM and loads. At some point a small diameter pipe will become flow restrictive and will need to be larger, but the trade off is loss of low load velocity and increased pressure and you perceive this as loss of low RPM torque. A short straight pipe is best but you have packaging problems. If you have to have bends, the bends should be a larger diameter then the straight sections because you want the flow to slow down to reduce turbulence in the bend, but this really adds huge cost to the system. Now if you really want something slick, have all your bends take on the NACA duct peanut shape for the best possible flow. Mandrel bending prevents a smaller diameter then the straight and is usually the best you get.
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
__________________
Gadget
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
__________________
Gadget
There is more to fluid dynamics than wing theory (which as stated above has been incorrectly applied), and venturi effect.
Airplanes do not fly simply because the air travels faster over the top of the wing than it does over the bottom. Hydrodynamic lift requires a force be applied somewhere.
In an exhaust manifold, large pipes cause the pressure to be too low to affect efficient scavenging of the next cylinder in the firing sequence. I'll mention the straw in the glass of water again- blow softly, low pressure, and nothing... blow hard, high pressure, and the fluid moves up the straw. Blow hard through a straw, over another straw and the fluid moves even higher. Yes, high pressure can create low pressure....
And yes, the original post is contradicting itself.
Lest not us forget that accoustic effects have not even been taken into consideration by the 'information' provided in the post quoted by the poster I'm replying to.
11-05-2008, 08:17 AM
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Question....what happens when the two sides (passenger/driver sides) are unbalanced? The way it is set up stock, the 1 1/2" crossover feeds into the driver manifold. Driver manifold benefits from the suction of the escaping gasses from the pass side. So each side can't be equal can they?
What would happen if you had a straight pipe with a bottle neck situation? Let's say a 3" pipe (which most everyone on here agrees is too large) with a 2" restriction in the middle of it. Kinda like this: ==-== Or, think of it like it was clogged...same thing?
What would happen if you had a straight pipe with a bottle neck situation? Let's say a 3" pipe (which most everyone on here agrees is too large) with a 2" restriction in the middle of it. Kinda like this: ==-== Or, think of it like it was clogged...same thing?
11-06-2008, 04:43 AM
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I was just trying to relate diesel engine operation to something non-diesel familiar people might understand. It's true that diesel cannot pre-ignite. Spontaneous combustion is EXACTLY what causes diesel fuel to burn in a 4-cycle (otto?) engine. But for people from a 'gasoline' background, spontaneous combustion is bad... pre-ignition, pinging, spark-knock, detonation (though technically that is the wrong term to use, but can happen in a gas engine)... should I call it deflagration?
11-06-2008, 04:58 AM
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People saying you need backpressure yet again Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure.
Gadget explains this better than anyone..
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
Check this out, airplanes fly. They do this by managing flow dynamics also known as fluid dynamics. When you increase the velocity of a fluid its pressure decreases. When this decrease in pressure is above the wing, the pressure under the wing pushes up lifting the plane into the air. When you decrease the velocity its pressure increases. When air is drawn through a venturi in a carb the pressure drops and that is what draws the gas out of the bowl and into the air stream. If you look at a venturi you would think that it is a big restriction, but it causes the pressure to drop. A venturi is basically an airplane wing in a circle.
Now with an exhaust system you want the lowest pressure you can get so the engine works less hard pushing the exhaust out. So, it is all about flow management. A small pipe will cause the flow to be faster and it travels down that pipe in pulses. The faster it goes the less the pressure is especially after the pulse wave. If you get to big of a pipe the velocity slows down and the pressure increases. So a large diameter pipe can in fact result in a higher pressure in the pipe and cause the engine to work harder to push out the exhaust and you loose torque.
Do you want a visual aid? If so, light two candles. Place them about 6? apart. Now blow between them. You will notice that the flames lean toward the air that you are blowing between the candles. This is because the pressure between the candles dropped and the higher-pressure air is rushing to move toward the low-pressure air pushing the flames over as it passes through.
Now there are always compromises. Your engine runs at different RPMs and different loads and you will want the smallest diameter pipe possible without restricting high flow at high RPM and loads. At some point a small diameter pipe will become flow restrictive and will need to be larger, but the trade off is loss of low load velocity and increased pressure and you perceive this as loss of low RPM torque. A short straight pipe is best but you have packaging problems. If you have to have bends, the bends should be a larger diameter then the straight sections because you want the flow to slow down to reduce turbulence in the bend, but this really adds huge cost to the system. Now if you really want something slick, have all your bends take on the NACA duct peanut shape for the best possible flow. Mandrel bending prevents a smaller diameter then the straight and is usually the best you get.
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
__________________
Gadget
Too large of pipe will comprimise the horsepower, but it has nothing to do with needing backpressure. Gadget explains this better than anyone..
Quote:
Every time I hear this crap that our engines need back pressure I just shake my head. It is just the dumbest thing around. The Otto cycle engine does not need any backpressure. In fact the less backpressure the better. A suction in the exhaust is even better as it will help pull exhaust out of the cylinder so the engine will not have to use power to push it out.
Check this out, airplanes fly. They do this by managing flow dynamics also known as fluid dynamics. When you increase the velocity of a fluid its pressure decreases. When this decrease in pressure is above the wing, the pressure under the wing pushes up lifting the plane into the air. When you decrease the velocity its pressure increases. When air is drawn through a venturi in a carb the pressure drops and that is what draws the gas out of the bowl and into the air stream. If you look at a venturi you would think that it is a big restriction, but it causes the pressure to drop. A venturi is basically an airplane wing in a circle.
Now with an exhaust system you want the lowest pressure you can get so the engine works less hard pushing the exhaust out. So, it is all about flow management. A small pipe will cause the flow to be faster and it travels down that pipe in pulses. The faster it goes the less the pressure is especially after the pulse wave. If you get to big of a pipe the velocity slows down and the pressure increases. So a large diameter pipe can in fact result in a higher pressure in the pipe and cause the engine to work harder to push out the exhaust and you loose torque.
Do you want a visual aid? If so, light two candles. Place them about 6? apart. Now blow between them. You will notice that the flames lean toward the air that you are blowing between the candles. This is because the pressure between the candles dropped and the higher-pressure air is rushing to move toward the low-pressure air pushing the flames over as it passes through.
Now there are always compromises. Your engine runs at different RPMs and different loads and you will want the smallest diameter pipe possible without restricting high flow at high RPM and loads. At some point a small diameter pipe will become flow restrictive and will need to be larger, but the trade off is loss of low load velocity and increased pressure and you perceive this as loss of low RPM torque. A short straight pipe is best but you have packaging problems. If you have to have bends, the bends should be a larger diameter then the straight sections because you want the flow to slow down to reduce turbulence in the bend, but this really adds huge cost to the system. Now if you really want something slick, have all your bends take on the NACA duct peanut shape for the best possible flow. Mandrel bending prevents a smaller diameter then the straight and is usually the best you get.
It is all about managing flow velocities without becoming flow restrictive.
With headers designs, if you can decide what RPM you want the most power, you can tune your primary tube length so that the lower pressure portion of the pulse wave of one cylinder is passing the end of the primary tube that has the exhaust valve that is just opening so that primary tube will have the lowest pressure possible. This however can only be tuned to a specific RPM range and you also have to worry about packaging problems. Usually headers with big fat primary tubes will perform worse then ones with smaller tubes.
Now when you hear someone say that you need back pressure for low RPM torque they are exactly opposite of what is really going on. You want the least pressure possible in the pipe at low RPM (or any RPM) and larger pipe increases pressure because the velocity is much lower.
None of this applies to turbo systems. That is a whole other chapter on exhaust theory.
__________________
Gadget
jeez... how can you create 'suction' across a pipe? no pressure does nothing to do so. try looking at a straw in a glass of water... that's about the least possible pressure you can apply. Now try blowing across the straw... what happens? The water in the glass moves up the straw. So, explain to me how adding pressure (blowing) creates suction?
we're already off to a bad start here.
Okay, I'm there with you for a moment... but since you're talking fluid dynamics... angle of attack, et all, come into play.
Someone really needs to rethink their knowledge of how planes fly. When you increase the velocity of a fluid, the pressure increases. If what was said is true, blow into an anemometer. If pressure decreases when velocity increases, air pressure should drop.
It's only when the fluid travels over a restricted / confined space that the pressure decreases within that space.
If you actually graph the pressure exerted on the wing of an airplane, there is a net-zero effect. In order to fly, the wing must exert force against something else. Now, using a wing to describe fluid motion and pressure gradients within a confined space isn't exactly the best way to do so. Matter-of-factly, it's just plain-and-simple wrong.
And a venturi is not the same thing as a wing. Show me how 'wing theory' relates to pressure gradients caused by air flow across the open end of a cylinder.
NO. A small pipe, if too small, will reduce the velocity the gasses have since the relationship between velocity and pressure is determined by the cross section of the pipe... oh wait... now there's an argument for having some pressure in the pipe? Too large of a pipe and the pressure drops?
been there, done that... and the candles flickered. Now when I put them about 6" apart and blow, yeah, they kind of lean towards the breath but then quite quickly and violently flutter about due to the turbulent air-flow around them.
But when I blew through a straw, they were both drawn towards the air flow, with little sign of the turbulence seen before....
I give up... nothing above addressed the issue of accoustics and flow management. Nothing mentioned above contradicts what I've said before.
There is more to fluid dynamics than wing theory (which as stated above has been incorrectly applied), and venturi effect.
Airplanes do not fly simply because the air travels faster over the top of the wing than it does over the bottom. Hydrodynamic lift requires a force be applied somewhere.
In an exhaust manifold, large pipes cause the pressure to be too low to affect efficient scavenging of the next cylinder in the firing sequence. I'll mention the straw in the glass of water again- blow softly, low pressure, and nothing... blow hard, high pressure, and the fluid moves up the straw. Blow hard through a straw, over another straw and the fluid moves even higher. Yes, high pressure can create low pressure....
And yes, the original post is contradicting itself.
Lest not us forget that accoustic effects have not even been taken into consideration by the 'information' provided in the post quoted by the poster I'm replying to.
we're already off to a bad start here.
Okay, I'm there with you for a moment... but since you're talking fluid dynamics... angle of attack, et all, come into play.
Someone really needs to rethink their knowledge of how planes fly. When you increase the velocity of a fluid, the pressure increases. If what was said is true, blow into an anemometer. If pressure decreases when velocity increases, air pressure should drop.
It's only when the fluid travels over a restricted / confined space that the pressure decreases within that space.
If you actually graph the pressure exerted on the wing of an airplane, there is a net-zero effect. In order to fly, the wing must exert force against something else. Now, using a wing to describe fluid motion and pressure gradients within a confined space isn't exactly the best way to do so. Matter-of-factly, it's just plain-and-simple wrong.
And a venturi is not the same thing as a wing. Show me how 'wing theory' relates to pressure gradients caused by air flow across the open end of a cylinder.
NO. A small pipe, if too small, will reduce the velocity the gasses have since the relationship between velocity and pressure is determined by the cross section of the pipe... oh wait... now there's an argument for having some pressure in the pipe? Too large of a pipe and the pressure drops?
been there, done that... and the candles flickered. Now when I put them about 6" apart and blow, yeah, they kind of lean towards the breath but then quite quickly and violently flutter about due to the turbulent air-flow around them.
But when I blew through a straw, they were both drawn towards the air flow, with little sign of the turbulence seen before....
I give up... nothing above addressed the issue of accoustics and flow management. Nothing mentioned above contradicts what I've said before.
There is more to fluid dynamics than wing theory (which as stated above has been incorrectly applied), and venturi effect.
Airplanes do not fly simply because the air travels faster over the top of the wing than it does over the bottom. Hydrodynamic lift requires a force be applied somewhere.
In an exhaust manifold, large pipes cause the pressure to be too low to affect efficient scavenging of the next cylinder in the firing sequence. I'll mention the straw in the glass of water again- blow softly, low pressure, and nothing... blow hard, high pressure, and the fluid moves up the straw. Blow hard through a straw, over another straw and the fluid moves even higher. Yes, high pressure can create low pressure....
And yes, the original post is contradicting itself.
Lest not us forget that accoustic effects have not even been taken into consideration by the 'information' provided in the post quoted by the poster I'm replying to.
http://en.wikipedia.org/wiki/Bernoulli's_principle
In a ventury the pressure in front of the restriction is high but the pressure in the ventury is less due to the increase in velocity. Thats just they way it is. Its been proven. You cant disprove it. Its like trying to argue that gravity does not exist. High velocity eqals low pressure. No velocity equals high pressure.
Last edited by saitotiktmdog; 11-06-2008 at 05:04 AM.
11-06-2008, 07:56 AM
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There are a lot of innaccuracies in both of these statements but i fear the latter has the most. My physics in college and my fluid dynamics class in college help out in that. Seems like someone needs to brush up on his bernoulli principle.
http://en.wikipedia.org/wiki/Bernoulli's_principle
In a ventury the pressure in front of the restriction is high but the pressure in the ventury is less due to the increase in velocity. Thats just they way it is. Its been proven. You cant disprove it. Its like trying to argue that gravity does not exist. High velocity eqals low pressure. No velocity equals high pressure.
http://en.wikipedia.org/wiki/Bernoulli's_principle
In a ventury the pressure in front of the restriction is high but the pressure in the ventury is less due to the increase in velocity. Thats just they way it is. Its been proven. You cant disprove it. Its like trying to argue that gravity does not exist. High velocity eqals low pressure. No velocity equals high pressure.
It's only when the fluid travels over a restricted / confined space that the pressure decreases within that space.
11-06-2008, 10:21 AM
#76
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when i first got my truck it had the stock cat and stock exhaust pipe cut off in front of where the muffler used to be. it had been like that for about 6 months before i got, and about a month after i got it. it was perdy loud. and had no problems.but i had to get a muffler put on bc it wouldnt pass inspection
11-07-2008, 04:30 PM
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I'd have to disagree. Maybe the way you use the glasspack(s) can hurt you, but not the glasspack itself.
Case-in-point:
1981 VW Scirocco, 1.7l 8v. I replaced the exhaust from the converter back with 2", into a 14" glasspack installed backwards, then 2" pipe (crush bent at the muffler shop) up and over the rear suspension into a 12" glasspack mounted normally into the exhaust tip (mentioned below). Granted, not a horsepower monster by any means but without any other mods to the engine it went from being the economy vehicle it was (35+ mpg on the highway) to CRX killer (well, up to about 90 miles per hour). 3rd gear tire chirps were no problem for it.
I originally had an 18" glasspack mounted normally where the 14" listed above was mounted and then 2" pipe into a dual 'monza' resonator tip (wow... 80's reference?). Took it back to the shop because it was too loud. So we looked at things and decided to go down to a 14" pack in reverse and add the 12" in front of the monza tip. Got it back and it was all nice and growly, nearly ricer, but without that tounge-between-the-lips-and-blow resonance... sounded more like a modern ducati motorcycle than rice-rocket... and actually performed better.
Case-in-point:
1981 VW Scirocco, 1.7l 8v. I replaced the exhaust from the converter back with 2", into a 14" glasspack installed backwards, then 2" pipe (crush bent at the muffler shop) up and over the rear suspension into a 12" glasspack mounted normally into the exhaust tip (mentioned below). Granted, not a horsepower monster by any means but without any other mods to the engine it went from being the economy vehicle it was (35+ mpg on the highway) to CRX killer (well, up to about 90 miles per hour). 3rd gear tire chirps were no problem for it.
I originally had an 18" glasspack mounted normally where the 14" listed above was mounted and then 2" pipe into a dual 'monza' resonator tip (wow... 80's reference?). Took it back to the shop because it was too loud. So we looked at things and decided to go down to a 14" pack in reverse and add the 12" in front of the monza tip. Got it back and it was all nice and growly, nearly ricer, but without that tounge-between-the-lips-and-blow resonance... sounded more like a modern ducati motorcycle than rice-rocket... and actually performed better.
11-07-2008, 04:44 PM
#78
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care to elaborate?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
Last edited by abecedarian; 11-07-2008 at 04:51 PM.
11-10-2008, 12:57 PM
#79
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Join Date: Nov 2007
Location: Indiana
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care to elaborate?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
http://www.freedomflightinc.com/Basi...arachutes.html
http://www.engineersedge.com/hydraul...low_menu.shtml
11-10-2008, 12:59 PM
#80
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Join Date: Nov 2007
Location: Indiana
Posts: 776
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care to elaborate?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
for the most part, high velocity does cause more pressure to be exerted...
so let's assume a pipe with whichever cross-section you desire... and a fluid with any arbitrary temperature...
... any acceleration of the fluid within the pipe will cause an increase in pressure applied at the terminus of the pipe.
If that weren't true, power steering pumps wouldn't work, tractors couldn't move mountains, automatic transmissions couldn't operate... and turbochargers wouldn't work.
...and feel free to quote my posts (in particular the one you say had many flaws) to demonstrate my deficiencies.
and while you're at it, explain why spinning the oil pump on your truck faster, in lock-step with engine rpm's, does not cause higher pressure... which any pressure gauge would disagree with.... because higher velocity does not cause higher pressure, right?
we are talking fluid dynamics, no?
Last edited by saitotiktmdog; 11-10-2008 at 01:03 PM.
