can i run open headers
Thread Starter
Racer
Joined: Aug 2010
Posts: 263
Likes: 0
From: bethpage NY
thanks i appreciate the advice im still not sure what i want to do tho. i have to chop the exhaust thats on there now due to having to modify the xmember for the 700r4 swap im doing so i may just throw a 90 on and go right out the side either behind the front wheel or in front of the rear wheel. and i am no neighborhood friend 
Instructor
Joined: Mar 2010
Posts: 162
Likes: 8
One of the motorcycle forums I frequent had the same thing questions about backpressure once. Basically, an engine is an air pump. It is all about exhaust sizing. If a pipe is too large the exhaust will cool down before it leaves the pipe and cause the engine to work harder to get the exhaust out. A bend is put in the pipe and that bend causes the exhaust to speed up due to physics and fluid dynamics. This causes the engine to work less to move the same amount of air so it makes more power. The incorrect conclusion is then drawn that the big open pipe didnt cause enough back pressure so it hurt performance. In reality if the pipe were smaller it could be completely straight. At least that is the research that I looked up years ago.
Thread Starter
Racer
Joined: Aug 2010
Posts: 263
Likes: 0
From: bethpage NY
Never considered backpressure as being an engine's friend, but that's another topic. In any event, with open headers the pressure you'll receive from your neighbors and the authorities will be your problem. Heck, some tracks and sanctioning bodies even have noise limitations...
Intermediate
Joined: Jun 2010
Posts: 39
Likes: 0
From: Louisville Kentucky
It's coincidental to read two different forums about two similar topics in one day. Corvette vs. F1
Just my 2 cents:
From what I have read, raising back pressure doesn't increase performance as far as I know. But what IS important is the time and manner in which exhaust gas is handled. Opening intake valves with overlapping exhaust valves creates a pressure difference to induce the fresh air into the cylinder faster. Seemingly relevant in motors that operate at high rev bands. (This is just what how I interpreted things.)
Here is a link to a brief article:
http://www.f1technical.net/forum/vie....php?f=4&t=493
‘The moment the outlet valves open, all hell is let loose. One of the 10 cylinders in an f1 engine has just inhaled 300cc of air, laced it with a jet of fuel, compressed the mixture to 10x atmospheric pressure and flung in a spark. At 900 degrees Celsius the gasses produced when the mixture explodes whip past the titanium outlet valves and into the exhaust system at the speed of sound. But far from being a simple means of evacuating hot, high-speed gases, modern exhaust systems have a crucial part to play in determining the power and performance of a racing engine.
Compared with the exhaust of a road-going car, the short but serpentine system in a formula racer looks pretty simple. Each bank of cylinders features a number of artistically twisted steel tubes, with no catalytic converter and no silencer to hinder the flow of the exhaust gases and prevent the engine breathing freely. And yet designing a F1 exhaust system is an extremely complex business that calls for an intimate knowledge of the laws of acoustics if the engineers are to tease the last reserves of power out of the engine. That’s because, like in a trumpet, the exhaust gases vibrate at a specific frequency depending on the speed of the engine. As the valves open and close, they generate a pulsating column of exhaust, with regular peaks and troughs of pressure. To ensure that the 5 cylinders per bank don’t interfere with one another in this respect, all the exhaust pipes must be the same length. And at the end of the collector, the exhaust gasses from each bank exit the car from a single tailpipe.
Racing engines bred for maximum power work with a high degree of valve overlap. That is to say, the inlet valves are opened before the piston reaches top dead center (TDC) while the outlet valves are still open. At this instant, a perfectly tuned exhaust system will ensure that there is already under pressure in the combustion chamber, drawing in the mixture for the next charge. So the induction stroke which is generally triggered by the downward motion of the piston is in this case initiated by the exhaust system . Thus the intake and exhaust system together form an integrated and highly sensitive gas vibration system which influences both maximum power and torque.
At peak revs, a formula engine will blast out exhaust gases 95,000 times a minute. To scavenge maximum power the exhaust pipes need to be as short as possible. Unfortunately , to help generate maximum torque and responsiveness at lower revs, longer splender pipes are called for. As F1 regulations don’t permit variable-geometry exhausts, the answer lies in the best possible compromise.
The current preference for tailpipes that emerge upwards through the rear trim at either side of the car has made life easier for exhaust designers.
Nevertheless, F1 exhausts rarely completes more than 1200km since the need to save weight means they have to be designed close to the limit. The thickness of the heat-resistant steel adopted from the aerospace industry varies but is never more than 1 millimeter. But when eventually kills these waste-gas works of art is not vibration or temperatures of 1000 degrees and more, but stress, The different radii of the various pipes ultimately produce fatigue which leads to cracks where the stress is greatest. Not surprisingly, at this high level of performance even the best exhaust are soon exhausted !!’
Just my 2 cents:
From what I have read, raising back pressure doesn't increase performance as far as I know. But what IS important is the time and manner in which exhaust gas is handled. Opening intake valves with overlapping exhaust valves creates a pressure difference to induce the fresh air into the cylinder faster. Seemingly relevant in motors that operate at high rev bands. (This is just what how I interpreted things.)
Here is a link to a brief article:
http://www.f1technical.net/forum/vie....php?f=4&t=493
‘The moment the outlet valves open, all hell is let loose. One of the 10 cylinders in an f1 engine has just inhaled 300cc of air, laced it with a jet of fuel, compressed the mixture to 10x atmospheric pressure and flung in a spark. At 900 degrees Celsius the gasses produced when the mixture explodes whip past the titanium outlet valves and into the exhaust system at the speed of sound. But far from being a simple means of evacuating hot, high-speed gases, modern exhaust systems have a crucial part to play in determining the power and performance of a racing engine.
Compared with the exhaust of a road-going car, the short but serpentine system in a formula racer looks pretty simple. Each bank of cylinders features a number of artistically twisted steel tubes, with no catalytic converter and no silencer to hinder the flow of the exhaust gases and prevent the engine breathing freely. And yet designing a F1 exhaust system is an extremely complex business that calls for an intimate knowledge of the laws of acoustics if the engineers are to tease the last reserves of power out of the engine. That’s because, like in a trumpet, the exhaust gases vibrate at a specific frequency depending on the speed of the engine. As the valves open and close, they generate a pulsating column of exhaust, with regular peaks and troughs of pressure. To ensure that the 5 cylinders per bank don’t interfere with one another in this respect, all the exhaust pipes must be the same length. And at the end of the collector, the exhaust gasses from each bank exit the car from a single tailpipe.
Racing engines bred for maximum power work with a high degree of valve overlap. That is to say, the inlet valves are opened before the piston reaches top dead center (TDC) while the outlet valves are still open. At this instant, a perfectly tuned exhaust system will ensure that there is already under pressure in the combustion chamber, drawing in the mixture for the next charge. So the induction stroke which is generally triggered by the downward motion of the piston is in this case initiated by the exhaust system . Thus the intake and exhaust system together form an integrated and highly sensitive gas vibration system which influences both maximum power and torque.
At peak revs, a formula engine will blast out exhaust gases 95,000 times a minute. To scavenge maximum power the exhaust pipes need to be as short as possible. Unfortunately , to help generate maximum torque and responsiveness at lower revs, longer splender pipes are called for. As F1 regulations don’t permit variable-geometry exhausts, the answer lies in the best possible compromise.
The current preference for tailpipes that emerge upwards through the rear trim at either side of the car has made life easier for exhaust designers.
Nevertheless, F1 exhausts rarely completes more than 1200km since the need to save weight means they have to be designed close to the limit. The thickness of the heat-resistant steel adopted from the aerospace industry varies but is never more than 1 millimeter. But when eventually kills these waste-gas works of art is not vibration or temperatures of 1000 degrees and more, but stress, The different radii of the various pipes ultimately produce fatigue which leads to cracks where the stress is greatest. Not surprisingly, at this high level of performance even the best exhaust are soon exhausted !!’
Navigator
Joined: Jul 2010
Posts: 9
Likes: 0
closest thing i've had to that was on a honda vtx and it messed up a valve but it also didn't have any pipes on it and some guy came up and started it while i had them off to hear what it sounded like. On my '75 i ran electric cut-outs to do strait header and put duals out the back for street driving
