no exhaust
#22
06-09-2011, 04:43 AM
Kid are you serious? 
I understand you want instant gratification with your wants and can't wait until the money is available, but come on. If you want it to be louder for the time being take some of the packing out of the can to make it louder. DON'T take it all out because then your back to the scenario I mentioned before about having to rejet your carbs because of it leaning out.
OR
Focus on the important things like throttle control, braking, proper body positioning and cornering while you save up for the slip-on.
I understand you want instant gratification with your wants and can't wait until the money is available, but come on. If you want it to be louder for the time being take some of the packing out of the can to make it louder. DON'T take it all out because then your back to the scenario I mentioned before about having to rejet your carbs because of it leaning out.
OR
Focus on the important things like throttle control, braking, proper body positioning and cornering while you save up for the slip-on.
#23
07-08-2011, 09:57 AM
#24
07-09-2011, 02:09 PM
Senior Member
I can’t believe this “you need back pressure” BS still exists. Back pressure is NOT a good thing! EVER! PERIOD! Don't try to argue it because it shows you obviously don't have a clue how exhaust scavenging works. The ideal exhaust system will have ZERO/NONE/ZIP/NADA back pressure. Back pressure is a parasitic loss as it causes the piston to force exhaust gas out of the chamber.
Exhaust scavenging is an entirely different situation and it related to many things, all of which have nothing to do with the muffler. By the time the exhaust gets to the muffler, it is far too cool and way too far from the exhaust valve to assist anything. A vehicle will ALWAYS go faster without a muffler on it, if only because of lost weight. A lot of times the reason people need to re-jet after a muffler swap because they removed a restrictive muffler, flow more exhaust, and go lean as a result. That or they change something else at the same time and blame the muffler.
Exhaust scavenging takes place in the cylinder head ports, header primaries, and collector (depending on the type/shape/etc.). Coupled with valve event timing, pulse phases, etc., all cause race teams spend $1000s of dollars finding exactly what will work with their specific operating conditions. It happens because the pressure waves that leave the combustion chamber reach some point, turn around, travel back up the pipe, turn around again at the chamber and return. Easiest way to think of them is ripples in a pond. If the ripples couple together, they get stronger. If they collide, they cancel. An ideally sized exhaust system will have primaries that focus and amplify the wave signals in order to increase the coupling strength.
The catch is that the requirements for “ideal” change throughout the RPM band. Low RPM wants long tubes made of small pipe. The reason being that the time between exhaust valve events is long (relative) and the quantity of exhaust is relatively small. A small pipe remains “full” which prevents dead pockets, keeps the gas hot, and maintains velocity (but does NOT cause back pressure). In comparison, high RPM needs short tubes made of big pipe due to short time between exhaust events and lots of exhaust flowing (ever notice how short pro-stock drag headers are basically 8 short pipes out the cylinder head). A race team that keeps a motor at or near a specific RPM mile after mile can decide exactly what they want and focus their design to hit the maximum output. With street use though, RPM is all over the place. So as a results street headers are made with a compromises to usually focus in the upper mid-range target area and make the “sweet spot” as wide as possible to bridge as much area as possible.
Exhaust scavenging is an entirely different situation and it related to many things, all of which have nothing to do with the muffler. By the time the exhaust gets to the muffler, it is far too cool and way too far from the exhaust valve to assist anything. A vehicle will ALWAYS go faster without a muffler on it, if only because of lost weight. A lot of times the reason people need to re-jet after a muffler swap because they removed a restrictive muffler, flow more exhaust, and go lean as a result. That or they change something else at the same time and blame the muffler.
Exhaust scavenging takes place in the cylinder head ports, header primaries, and collector (depending on the type/shape/etc.). Coupled with valve event timing, pulse phases, etc., all cause race teams spend $1000s of dollars finding exactly what will work with their specific operating conditions. It happens because the pressure waves that leave the combustion chamber reach some point, turn around, travel back up the pipe, turn around again at the chamber and return. Easiest way to think of them is ripples in a pond. If the ripples couple together, they get stronger. If they collide, they cancel. An ideally sized exhaust system will have primaries that focus and amplify the wave signals in order to increase the coupling strength.
The catch is that the requirements for “ideal” change throughout the RPM band. Low RPM wants long tubes made of small pipe. The reason being that the time between exhaust valve events is long (relative) and the quantity of exhaust is relatively small. A small pipe remains “full” which prevents dead pockets, keeps the gas hot, and maintains velocity (but does NOT cause back pressure). In comparison, high RPM needs short tubes made of big pipe due to short time between exhaust events and lots of exhaust flowing (ever notice how short pro-stock drag headers are basically 8 short pipes out the cylinder head). A race team that keeps a motor at or near a specific RPM mile after mile can decide exactly what they want and focus their design to hit the maximum output. With street use though, RPM is all over the place. So as a results street headers are made with a compromises to usually focus in the upper mid-range target area and make the “sweet spot” as wide as possible to bridge as much area as possible.
#25
07-10-2011, 10:44 AM
Senior Member
Join Date: Jan 2011
Location: Springfield MA
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I can’t believe this “you need back pressure” BS still exists. Back pressure is NOT a good thing! EVER! PERIOD! Don't try to argue it because it shows you obviously don't have a clue how exhaust scavenging works. The ideal exhaust system will have ZERO/NONE/ZIP/NADA back pressure. Back pressure is a parasitic loss as it causes the piston to force exhaust gas out of the chamber.
Exhaust scavenging is an entirely different situation and it related to many things, all of which have nothing to do with the muffler. By the time the exhaust gets to the muffler, it is far too cool and way too far from the exhaust valve to assist anything. A vehicle will ALWAYS go faster without a muffler on it, if only because of lost weight. A lot of times the reason people need to re-jet after a muffler swap because they removed a restrictive muffler, flow more exhaust, and go lean as a result. That or they change something else at the same time and blame the muffler.
Exhaust scavenging takes place in the cylinder head ports, header primaries, and collector (depending on the type/shape/etc.). Coupled with valve event timing, pulse phases, etc., all cause race teams spend $1000s of dollars finding exactly what will work with their specific operating conditions. It happens because the pressure waves that leave the combustion chamber reach some point, turn around, travel back up the pipe, turn around again at the chamber and return. Easiest way to think of them is ripples in a pond. If the ripples couple together, they get stronger. If they collide, they cancel. An ideally sized exhaust system will have primaries that focus and amplify the wave signals in order to increase the coupling strength.
The catch is that the requirements for “ideal” change throughout the RPM band. Low RPM wants long tubes made of small pipe. The reason being that the time between exhaust valve events is long (relative) and the quantity of exhaust is relatively small. A small pipe remains “full” which prevents dead pockets, keeps the gas hot, and maintains velocity (but does NOT cause back pressure). In comparison, high RPM needs short tubes made of big pipe due to short time between exhaust events and lots of exhaust flowing (ever notice how short pro-stock drag headers are basically 8 short pipes out the cylinder head). A race team that keeps a motor at or near a specific RPM mile after mile can decide exactly what they want and focus their design to hit the maximum output. With street use though, RPM is all over the place. So as a results street headers are made with a compromises to usually focus in the upper mid-range target area and make the “sweet spot” as wide as possible to bridge as much area as possible.
Exhaust scavenging is an entirely different situation and it related to many things, all of which have nothing to do with the muffler. By the time the exhaust gets to the muffler, it is far too cool and way too far from the exhaust valve to assist anything. A vehicle will ALWAYS go faster without a muffler on it, if only because of lost weight. A lot of times the reason people need to re-jet after a muffler swap because they removed a restrictive muffler, flow more exhaust, and go lean as a result. That or they change something else at the same time and blame the muffler.
Exhaust scavenging takes place in the cylinder head ports, header primaries, and collector (depending on the type/shape/etc.). Coupled with valve event timing, pulse phases, etc., all cause race teams spend $1000s of dollars finding exactly what will work with their specific operating conditions. It happens because the pressure waves that leave the combustion chamber reach some point, turn around, travel back up the pipe, turn around again at the chamber and return. Easiest way to think of them is ripples in a pond. If the ripples couple together, they get stronger. If they collide, they cancel. An ideally sized exhaust system will have primaries that focus and amplify the wave signals in order to increase the coupling strength.
The catch is that the requirements for “ideal” change throughout the RPM band. Low RPM wants long tubes made of small pipe. The reason being that the time between exhaust valve events is long (relative) and the quantity of exhaust is relatively small. A small pipe remains “full” which prevents dead pockets, keeps the gas hot, and maintains velocity (but does NOT cause back pressure). In comparison, high RPM needs short tubes made of big pipe due to short time between exhaust events and lots of exhaust flowing (ever notice how short pro-stock drag headers are basically 8 short pipes out the cylinder head). A race team that keeps a motor at or near a specific RPM mile after mile can decide exactly what they want and focus their design to hit the maximum output. With street use though, RPM is all over the place. So as a results street headers are made with a compromises to usually focus in the upper mid-range target area and make the “sweet spot” as wide as possible to bridge as much area as possible.
thanks for the lesson of the day
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