Backpressure?
12-21-2006, 07:43 AM
#24
Multi-Tasking Moderator!
Join Date: Nov 2006
Location: Detroit Rock City!
Posts: 15,618
RE: Backpressure?
Great explanation couldn't have said it better myself!!!!!!!
ORIGINAL: NickSezz
I always wondered why people talk about back pressure so much here... It is usully used as a term when talkin about 2-stroke engines. They don't have valves to control fuel and exhaust flowandrely onpressure waves from a tuned (shape tuned) exhaust pipe.
These pressure waves come out of the exhaust port, run through the header, and through a usally weird shaped tuned pipe that is designed to change the pressure waves' shape and speed. By doing so, the waves bounce back through the exhaust system and force more air and fuel into the engine through the exhaust portcreating a super charging effect. Remember, 2 stroke engines are not as efficient as 4 strokes are because they release exhaust gas during the same stroke as the new air and fuel enters the combustion chamber. During this time, some of the new air and fuel is wasted and lost out of the exhaust port of the engine. Without a tuned pipe, this can only be controlled by thelocation and offset of the ports in the crake case in realtion the the timing and travel of the piston. By adding the tuned pipe that creates a controlled back pressure wave, it forces that unburnt air and fuel back into the engine at the right time to create a larger explosion.
From my work with Nirto Rc cars, in general, a longer or fatter header pipe inceased low end power and torque, while ashorter or skinnier header made top end better. The tuned pipes are simple shaped for these small engines andare usually cone shapped, long and fat, or long a skinny. The cone shaped pipe created the best all round power by starting skinny and ending fat. The fat pipe creates more torque, and the skinny pipe was good for top end. For example: If you wanted good low end as well as pretty good top end, you could add a larger fatter header with a long skinny pipe. In general--More back pressure, more top end. Less back pressure, more low end. All of these principles apply to other 2 stroke engines like the goped I used to have and dirt bikes, but they are a little more complicated.
Now taking in terms of a 4 stroke. Since there are valves that contol the intake and exhaust flow, a special pipe in not needed for help. As I always heard, you want to get the exhaust gas out of the engine as fast as possible so new air and fuel can enter. This calls for a simple and large opening for the gas to escape. Done. Easy. I say the best exhaust system is no exhaust system.
Do you see top fuel dragsters with complicated exhausts? NO. They have large headers that point up. They burn Nirto Methane, and let me tell you, that Sh*t burns the hell out of your nose if you breath in theexhaust fumes. The headers direct that gas away from the car, as well as create down force on the car. Yes thats right down force! So much air is coming out of those pipes that when pointed up, it pushes the car down. If you ever saw a race where a few cylinders go out on a car, it starts to move around on the track more.
Now applying this to a modern mustang. Our cars sadly have computers now. This means that the chages we are aware of, the computer might not be. Changing the exhaust on the car will change the readings the O2 sensors are getting as well as some other things I probably don't know about. This is what causes a gain, or maybe a loss in performance as well as the exhaust letting air out faster. Blame the computer, not your exhaust system! I think that is whats being confused with back pressure, a simple 10101010101 error.
All I have said may not bee 100% accurate or complete, I am just throwing out what I know to help you guys. If someone has a correction for me I would be happy to accept as I am still learning and always love to learn more. Later --Nick
I always wondered why people talk about back pressure so much here... It is usully used as a term when talkin about 2-stroke engines. They don't have valves to control fuel and exhaust flowandrely onpressure waves from a tuned (shape tuned) exhaust pipe.
These pressure waves come out of the exhaust port, run through the header, and through a usally weird shaped tuned pipe that is designed to change the pressure waves' shape and speed. By doing so, the waves bounce back through the exhaust system and force more air and fuel into the engine through the exhaust portcreating a super charging effect. Remember, 2 stroke engines are not as efficient as 4 strokes are because they release exhaust gas during the same stroke as the new air and fuel enters the combustion chamber. During this time, some of the new air and fuel is wasted and lost out of the exhaust port of the engine. Without a tuned pipe, this can only be controlled by thelocation and offset of the ports in the crake case in realtion the the timing and travel of the piston. By adding the tuned pipe that creates a controlled back pressure wave, it forces that unburnt air and fuel back into the engine at the right time to create a larger explosion.
From my work with Nirto Rc cars, in general, a longer or fatter header pipe inceased low end power and torque, while ashorter or skinnier header made top end better. The tuned pipes are simple shaped for these small engines andare usually cone shapped, long and fat, or long a skinny. The cone shaped pipe created the best all round power by starting skinny and ending fat. The fat pipe creates more torque, and the skinny pipe was good for top end. For example: If you wanted good low end as well as pretty good top end, you could add a larger fatter header with a long skinny pipe. In general--More back pressure, more top end. Less back pressure, more low end. All of these principles apply to other 2 stroke engines like the goped I used to have and dirt bikes, but they are a little more complicated.
Now taking in terms of a 4 stroke. Since there are valves that contol the intake and exhaust flow, a special pipe in not needed for help. As I always heard, you want to get the exhaust gas out of the engine as fast as possible so new air and fuel can enter. This calls for a simple and large opening for the gas to escape. Done. Easy. I say the best exhaust system is no exhaust system.
Do you see top fuel dragsters with complicated exhausts? NO. They have large headers that point up. They burn Nirto Methane, and let me tell you, that Sh*t burns the hell out of your nose if you breath in theexhaust fumes. The headers direct that gas away from the car, as well as create down force on the car. Yes thats right down force! So much air is coming out of those pipes that when pointed up, it pushes the car down. If you ever saw a race where a few cylinders go out on a car, it starts to move around on the track more.
Now applying this to a modern mustang. Our cars sadly have computers now. This means that the chages we are aware of, the computer might not be. Changing the exhaust on the car will change the readings the O2 sensors are getting as well as some other things I probably don't know about. This is what causes a gain, or maybe a loss in performance as well as the exhaust letting air out faster. Blame the computer, not your exhaust system! I think that is whats being confused with back pressure, a simple 10101010101 error.
All I have said may not bee 100% accurate or complete, I am just throwing out what I know to help you guys. If someone has a correction for me I would be happy to accept as I am still learning and always love to learn more. Later --Nick
12-22-2006, 12:57 AM
#26
4th Gear Member
Join Date: May 2006
Location: Nutley NJ
Posts: 1,207
RE: Backpressure?
Greatly appreciated!!
ORIGINAL: mygt500
Great explanation couldn't have said it better myself!!!!!!!
Great explanation couldn't have said it better myself!!!!!!!
ORIGINAL: NickSezz
I always wondered why people talk about back pressure so much here... It is usully used as a term when talkin about 2-stroke engines. They don't have valves to control fuel and exhaust flowandrely onpressure waves from a tuned (shape tuned) exhaust pipe.
These pressure waves come out of the exhaust port, run through the header, and through a usally weird shaped tuned pipe that is designed to change the pressure waves' shape and speed. By doing so, the waves bounce back through the exhaust system and force more air and fuel into the engine through the exhaust portcreating a super charging effect. Remember, 2 stroke engines are not as efficient as 4 strokes are because they release exhaust gas during the same stroke as the new air and fuel enters the combustion chamber. During this time, some of the new air and fuel is wasted and lost out of the exhaust port of the engine. Without a tuned pipe, this can only be controlled by thelocation and offset of the ports in the crake case in realtion the the timing and travel of the piston. By adding the tuned pipe that creates a controlled back pressure wave, it forces that unburnt air and fuel back into the engine at the right time to create a larger explosion.
From my work with Nirto Rc cars, in general, a longer or fatter header pipe inceased low end power and torque, while ashorter or skinnier header made top end better. The tuned pipes are simple shaped for these small engines andare usually cone shapped, long and fat, or long a skinny. The cone shaped pipe created the best all round power by starting skinny and ending fat. The fat pipe creates more torque, and the skinny pipe was good for top end. For example: If you wanted good low end as well as pretty good top end, you could add a larger fatter header with a long skinny pipe. In general--More back pressure, more top end. Less back pressure, more low end. All of these principles apply to other 2 stroke engines like the goped I used to have and dirt bikes, but they are a little more complicated.
Now taking in terms of a 4 stroke. Since there are valves that contol the intake and exhaust flow, a special pipe in not needed for help. As I always heard, you want to get the exhaust gas out of the engine as fast as possible so new air and fuel can enter. This calls for a simple and large opening for the gas to escape. Done. Easy. I say the best exhaust system is no exhaust system.
Do you see top fuel dragsters with complicated exhausts? NO. They have large headers that point up. They burn Nirto Methane, and let me tell you, that Sh*t burns the hell out of your nose if you breath in theexhaust fumes. The headers direct that gas away from the car, as well as create down force on the car. Yes thats right down force! So much air is coming out of those pipes that when pointed up, it pushes the car down. If you ever saw a race where a few cylinders go out on a car, it starts to move around on the track more.
Now applying this to a modern mustang. Our cars sadly have computers now. This means that the chages we are aware of, the computer might not be. Changing the exhaust on the car will change the readings the O2 sensors are getting as well as some other things I probably don't know about. This is what causes a gain, or maybe a loss in performance as well as the exhaust letting air out faster. Blame the computer, not your exhaust system! I think that is whats being confused with back pressure, a simple 10101010101 error.
All I have said may not bee 100% accurate or complete, I am just throwing out what I know to help you guys. If someone has a correction for me I would be happy to accept as I am still learning and always love to learn more. Later --Nick
I always wondered why people talk about back pressure so much here... It is usully used as a term when talkin about 2-stroke engines. They don't have valves to control fuel and exhaust flowandrely onpressure waves from a tuned (shape tuned) exhaust pipe.
These pressure waves come out of the exhaust port, run through the header, and through a usally weird shaped tuned pipe that is designed to change the pressure waves' shape and speed. By doing so, the waves bounce back through the exhaust system and force more air and fuel into the engine through the exhaust portcreating a super charging effect. Remember, 2 stroke engines are not as efficient as 4 strokes are because they release exhaust gas during the same stroke as the new air and fuel enters the combustion chamber. During this time, some of the new air and fuel is wasted and lost out of the exhaust port of the engine. Without a tuned pipe, this can only be controlled by thelocation and offset of the ports in the crake case in realtion the the timing and travel of the piston. By adding the tuned pipe that creates a controlled back pressure wave, it forces that unburnt air and fuel back into the engine at the right time to create a larger explosion.
From my work with Nirto Rc cars, in general, a longer or fatter header pipe inceased low end power and torque, while ashorter or skinnier header made top end better. The tuned pipes are simple shaped for these small engines andare usually cone shapped, long and fat, or long a skinny. The cone shaped pipe created the best all round power by starting skinny and ending fat. The fat pipe creates more torque, and the skinny pipe was good for top end. For example: If you wanted good low end as well as pretty good top end, you could add a larger fatter header with a long skinny pipe. In general--More back pressure, more top end. Less back pressure, more low end. All of these principles apply to other 2 stroke engines like the goped I used to have and dirt bikes, but they are a little more complicated.
Now taking in terms of a 4 stroke. Since there are valves that contol the intake and exhaust flow, a special pipe in not needed for help. As I always heard, you want to get the exhaust gas out of the engine as fast as possible so new air and fuel can enter. This calls for a simple and large opening for the gas to escape. Done. Easy. I say the best exhaust system is no exhaust system.
Do you see top fuel dragsters with complicated exhausts? NO. They have large headers that point up. They burn Nirto Methane, and let me tell you, that Sh*t burns the hell out of your nose if you breath in theexhaust fumes. The headers direct that gas away from the car, as well as create down force on the car. Yes thats right down force! So much air is coming out of those pipes that when pointed up, it pushes the car down. If you ever saw a race where a few cylinders go out on a car, it starts to move around on the track more.
Now applying this to a modern mustang. Our cars sadly have computers now. This means that the chages we are aware of, the computer might not be. Changing the exhaust on the car will change the readings the O2 sensors are getting as well as some other things I probably don't know about. This is what causes a gain, or maybe a loss in performance as well as the exhaust letting air out faster. Blame the computer, not your exhaust system! I think that is whats being confused with back pressure, a simple 10101010101 error.
All I have said may not bee 100% accurate or complete, I am just throwing out what I know to help you guys. If someone has a correction for me I would be happy to accept as I am still learning and always love to learn more. Later --Nick
12-22-2006, 11:11 AM
#27
2nd Gear Member
Join Date: Sep 2006
Posts: 169
RE: Backpressure?
ORIGINAL: sa3geabx
I was talking to afriend at work about switching to dual exhaust on my car, and he told me without headers, the car would lose power because of backpressure. Can anyone confirm this? Is there anyone running duals without new headers that can feel a noticeable loss of power, and most importantly, are there any headers out on the market that I can install without voiding the warranty?
I was talking to afriend at work about switching to dual exhaust on my car, and he told me without headers, the car would lose power because of backpressure. Can anyone confirm this? Is there anyone running duals without new headers that can feel a noticeable loss of power, and most importantly, are there any headers out on the market that I can install without voiding the warranty?
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