Post by Luis on Jul 31, 2005 7:31:10 GMT -5
Headers
The idea behind an exhaust header is to eliminate the manifold's back pressure. A good way for an engine to lose power is during the exhaust stroke through backpressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted. It turns out that the manifold can be an important source of backpressure because exhaust gases from one cylinder built up pressure in the manifold that affects the next cylinder that uses the manifold. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. From there, the gases are passed through the rest of the exhaust system in a number of different ways.
The headers are usually the last piece of the puzzle of most people’s exhaust modifications. As explained in the mid-length section below, you must buy headers that will fit your mid-pipe. There are four types of headers, equal length headers, stock replacement/shorties, mid-length, and long tube. Aftermarket headers can be coated with processes like Jet Hot coating and ceramic coating. These are the most common. Others can be non-coated, or chromed. The coating helps to protect the headers from rusting and the helps to keep most of the heat in the header instead of allowing it to escape into the engine compartment. The degree to which the heat stays in the header is dependent on which coating is used with ceramic and Jet Hot coating being the best, followed by chrome, and finally non-coated headers.
Equal Length Headers
The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no backpressure generated by the cylinders sharing the collector.
Shorty Headers
These headers are a direct replacement for the stock manifolds. Typically they are better flowing and therefore help to free up more HP than the stock manifold and also allow the engine to produce more torque. Shortys are usually the least expensive and usually are the easiest to install. Installation typically runs approximately five hours or less for these headers. These headers can be installed by the average Mustang enthusiast with little tools (mainly just sockets) in the owner’s garage/driveway. With these headers, there is no need to purchase a different mid-pipe, as the current mid-pipe will bolt directly to them.
Mid-Length Headers
These headers are a mix between shortys and long tubes. The only company that manufactures these headers is Bassani. The install time is the same as the shortys. Mid-length headers either need Bassani’s matching mid-pipe or have a standard mid-pipe cut and welded to fit by a muffler shop. Mid length headers produce similar HP and TQ numbers as long tubes while allowing ground clearance with a lowered vehicle.
Long Tube Headers
These headers typically flow much better than any other header available and free the most HP possible. They also allow for significantly more torque to be produced by the engine. These headers are slightly more expensive than shortys and take approximately eight hours to install. When long tubes are used, a special “shorty” mid-pipe is required to bolt the exhaust together correctly. This increases the initial cost as the mid-pipe must be installed at the same time as the long tubes. While it is possible for the average Mustang owner to install long tubes in their garage/driveway, it is considerably more difficult to do so. Many people have muffler shops or professionals install their long tubes for this very reason.
Mid-Pipes
After the cat-back, the next piece of exhaust that is most frequently changed is the factory mid-pipe. All Mustangs come from the factory with an H pipe utilizing a 2 1/4” pipe as the mid pipe. Depending on the year of car you have, your stock mid pipe might have 4 or even 6 catalytic converters.
When you buy a new mid-pipe, all aftermarket mid-pipes are made with 2.5” piping and can be either aluminized steel or stainless steel. Like an aftermarket cat back, an aftermarket mid-pipe will connect to the exhaust headers and any cat back without the need for any modifications. These pipes do not require welding to attach the mid-pipe to the exhaust manifolds or to the cat-back systems. Depending on the type of header you decide to use (stock, shorty, or long tube) you will need to purchase the matching size H pipe or X pipe in order for everything to bolt up correctly. You can optionally choose to go with a true dual exhaust system consisting of no mid-pipe, but this will require some fabrication of piping to replace the now omitted mid-pipe.
The first thing you will need to decide on, is whether you want catalytic converters or not. In general, a catted mid-pipe is designed with one catalytic converter on each side of the pipe, this replaces the one or two cats found on each side of the stock H pipe. The cats that are used in aftermarket mid-pipes are what they call high-flowing cats as these are less restrictive than the stock cats. These pipes are typically street legal and will allow you to pass emissions tests, though you should check your state’s emissions laws just to make sure.
An off road mid-pipe, as the name implies, is not intended for street use, as there are no catalytic converters on the pipe, thus these pipes are illegal in all US states. Although many people use an off road pipe (one without catalytic converters) for just that reason, off road racing, and then switch to the stock for emissions testing and daily driving. These pipes will free up the most amount of Horse Power because there are no restrictions in the pipe. These pipes will also cause even a stock car to become considerably louder. The sound tends to be hollow, and you will typically smell unburned fuel in the exhaust gas much more so than a pipe that has catalytic converters.
X Vs. H Pipes
Now let’s discuss the two main designs for mid pipes, H and X type. An H pipe gets its name because there is a piece of pipe that connects each side of the pipe that connects to the header collectors (hence the name H pipe). This pipe is supposed to help equalize the pressure and thereby create a better scavenging effect. An X pipe however, has each side of the pipe meet in an X type junction. Again the idea is to equalize pressure and create better scavenging.
As a general rule, H pipes allow for more low-end torque and slightly less Horse Power than X pipes do. Also, the sound note is quite different. The X pipe has a raspy sound while the H pipe is more “muscle car” sounding. As mentioned, the mid-pipe choice seems to be a personal sound preference and most people who use chambered mufflers opt for the H pipe, while the straight through users tend to choose the X pipe. Typically, the X pipe/straight through muffler combination yields higher HP and lower torque than the H pipe/chambered muffler design. There is a third choice which only one manufacturer creates, and that is the MAC Pro-chamber, which consists of a box for a cross over.
The idea behind an exhaust header is to eliminate the manifold's back pressure. A good way for an engine to lose power is during the exhaust stroke through backpressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted. It turns out that the manifold can be an important source of backpressure because exhaust gases from one cylinder built up pressure in the manifold that affects the next cylinder that uses the manifold. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. From there, the gases are passed through the rest of the exhaust system in a number of different ways.
The headers are usually the last piece of the puzzle of most people’s exhaust modifications. As explained in the mid-length section below, you must buy headers that will fit your mid-pipe. There are four types of headers, equal length headers, stock replacement/shorties, mid-length, and long tube. Aftermarket headers can be coated with processes like Jet Hot coating and ceramic coating. These are the most common. Others can be non-coated, or chromed. The coating helps to protect the headers from rusting and the helps to keep most of the heat in the header instead of allowing it to escape into the engine compartment. The degree to which the heat stays in the header is dependent on which coating is used with ceramic and Jet Hot coating being the best, followed by chrome, and finally non-coated headers.
Equal Length Headers
The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no backpressure generated by the cylinders sharing the collector.
Shorty Headers
These headers are a direct replacement for the stock manifolds. Typically they are better flowing and therefore help to free up more HP than the stock manifold and also allow the engine to produce more torque. Shortys are usually the least expensive and usually are the easiest to install. Installation typically runs approximately five hours or less for these headers. These headers can be installed by the average Mustang enthusiast with little tools (mainly just sockets) in the owner’s garage/driveway. With these headers, there is no need to purchase a different mid-pipe, as the current mid-pipe will bolt directly to them.
Mid-Length Headers
These headers are a mix between shortys and long tubes. The only company that manufactures these headers is Bassani. The install time is the same as the shortys. Mid-length headers either need Bassani’s matching mid-pipe or have a standard mid-pipe cut and welded to fit by a muffler shop. Mid length headers produce similar HP and TQ numbers as long tubes while allowing ground clearance with a lowered vehicle.
Long Tube Headers
These headers typically flow much better than any other header available and free the most HP possible. They also allow for significantly more torque to be produced by the engine. These headers are slightly more expensive than shortys and take approximately eight hours to install. When long tubes are used, a special “shorty” mid-pipe is required to bolt the exhaust together correctly. This increases the initial cost as the mid-pipe must be installed at the same time as the long tubes. While it is possible for the average Mustang owner to install long tubes in their garage/driveway, it is considerably more difficult to do so. Many people have muffler shops or professionals install their long tubes for this very reason.
Mid-Pipes
After the cat-back, the next piece of exhaust that is most frequently changed is the factory mid-pipe. All Mustangs come from the factory with an H pipe utilizing a 2 1/4” pipe as the mid pipe. Depending on the year of car you have, your stock mid pipe might have 4 or even 6 catalytic converters.
When you buy a new mid-pipe, all aftermarket mid-pipes are made with 2.5” piping and can be either aluminized steel or stainless steel. Like an aftermarket cat back, an aftermarket mid-pipe will connect to the exhaust headers and any cat back without the need for any modifications. These pipes do not require welding to attach the mid-pipe to the exhaust manifolds or to the cat-back systems. Depending on the type of header you decide to use (stock, shorty, or long tube) you will need to purchase the matching size H pipe or X pipe in order for everything to bolt up correctly. You can optionally choose to go with a true dual exhaust system consisting of no mid-pipe, but this will require some fabrication of piping to replace the now omitted mid-pipe.
The first thing you will need to decide on, is whether you want catalytic converters or not. In general, a catted mid-pipe is designed with one catalytic converter on each side of the pipe, this replaces the one or two cats found on each side of the stock H pipe. The cats that are used in aftermarket mid-pipes are what they call high-flowing cats as these are less restrictive than the stock cats. These pipes are typically street legal and will allow you to pass emissions tests, though you should check your state’s emissions laws just to make sure.
An off road mid-pipe, as the name implies, is not intended for street use, as there are no catalytic converters on the pipe, thus these pipes are illegal in all US states. Although many people use an off road pipe (one without catalytic converters) for just that reason, off road racing, and then switch to the stock for emissions testing and daily driving. These pipes will free up the most amount of Horse Power because there are no restrictions in the pipe. These pipes will also cause even a stock car to become considerably louder. The sound tends to be hollow, and you will typically smell unburned fuel in the exhaust gas much more so than a pipe that has catalytic converters.
X Vs. H Pipes
Now let’s discuss the two main designs for mid pipes, H and X type. An H pipe gets its name because there is a piece of pipe that connects each side of the pipe that connects to the header collectors (hence the name H pipe). This pipe is supposed to help equalize the pressure and thereby create a better scavenging effect. An X pipe however, has each side of the pipe meet in an X type junction. Again the idea is to equalize pressure and create better scavenging.
As a general rule, H pipes allow for more low-end torque and slightly less Horse Power than X pipes do. Also, the sound note is quite different. The X pipe has a raspy sound while the H pipe is more “muscle car” sounding. As mentioned, the mid-pipe choice seems to be a personal sound preference and most people who use chambered mufflers opt for the H pipe, while the straight through users tend to choose the X pipe. Typically, the X pipe/straight through muffler combination yields higher HP and lower torque than the H pipe/chambered muffler design. There is a third choice which only one manufacturer creates, and that is the MAC Pro-chamber, which consists of a box for a cross over.
