Merge Collectors
01-02-2010, 07:13 AM
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Merge Collectors
Lots of reading going on lately. Merge collectors, anyone have any info on the differences between the vendors? Hedman, Stainless Headers Inc, Burns etc. They all look like solid pieces, just looking to learn a little more.
01-02-2010, 02:44 PM
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Collector Type -The collector merges all of the primary pipes together. There are designs ranging from cheap and simple to incredibly complex and costly. If you just joined the pipes in the simplest possible way you would have something that resembled the picture on the right.
The dead space in the middle of all of the pipes would cause a lot of turbulence and hinder flow. Eliminating the dead space is the main advantage of the merge collector. This is a more cost effective way to make the pipes join smoothly. Not quite as elegant as the merge collector, but still very good.
The bad daddy of all collectors is the merge collector. It is from Burns Stainless and is one of the finest collectors you can buy.
Collector Length -The length of the collector also plays a role in determining the powerband of the motor. Generally the longer the collector the more the powerband is shifted up. You also want enough length in the collector to smoothly join the gasses coming from the primary pipes. If the junction is too abrupt they do not interact very well causing turbulence, and again hindering flow. This is also another area of a lot of testing. The volume of the collector has a fairly big effect on the powerband of the motor.
Collector Width -The width of the collector helps control how well the exhaust pulses interact with each other. Make it too big and one pulse cannot help pull the next very well and the gasses can stagnate hurting flow. Make it too small and you hinder flow by causing too much backpressure. Yet another area to test.
Taper Angles - Basically you want the least amount of abrupt changes as possible. This mostly applies to the collector where it necks down to the diameter the exhaust will be. You do not want an abrupt angle as it will hinder flow.
The entries into the primary pipes from the head also have to be as close to the diameter of the exhaust ports as possible. This is so that you do not get yet another area for turbulence to get in the way of things. Protrusions into the gas flow should be avoided here most of all, as they have a much larger effect than in any other point in the system. According to many experts that do not play the marketing game, the stepped header designs are an attempt to cure other problems inherent in the design. The steps also add complexity and cost.
The lay-out of the car dictates a lot of how the header is made. The ports being on opposite sides of the Subaru engine do not make things easy when designing a header for our cars. Each change in length during testing requires almost making a new header on a Subaru boxer motor, thus the rather lengthy design process of our header. Getting lengths equal is definitely a big task given the packaging, and any variance within .5-1" is considered the mark of a top notch header designer.
if anyone cares, from cobbtuning.com
The dead space in the middle of all of the pipes would cause a lot of turbulence and hinder flow. Eliminating the dead space is the main advantage of the merge collector. This is a more cost effective way to make the pipes join smoothly. Not quite as elegant as the merge collector, but still very good.
The bad daddy of all collectors is the merge collector. It is from Burns Stainless and is one of the finest collectors you can buy.
Collector Length -The length of the collector also plays a role in determining the powerband of the motor. Generally the longer the collector the more the powerband is shifted up. You also want enough length in the collector to smoothly join the gasses coming from the primary pipes. If the junction is too abrupt they do not interact very well causing turbulence, and again hindering flow. This is also another area of a lot of testing. The volume of the collector has a fairly big effect on the powerband of the motor.
Collector Width -The width of the collector helps control how well the exhaust pulses interact with each other. Make it too big and one pulse cannot help pull the next very well and the gasses can stagnate hurting flow. Make it too small and you hinder flow by causing too much backpressure. Yet another area to test.
Taper Angles - Basically you want the least amount of abrupt changes as possible. This mostly applies to the collector where it necks down to the diameter the exhaust will be. You do not want an abrupt angle as it will hinder flow.
The entries into the primary pipes from the head also have to be as close to the diameter of the exhaust ports as possible. This is so that you do not get yet another area for turbulence to get in the way of things. Protrusions into the gas flow should be avoided here most of all, as they have a much larger effect than in any other point in the system. According to many experts that do not play the marketing game, the stepped header designs are an attempt to cure other problems inherent in the design. The steps also add complexity and cost.
The lay-out of the car dictates a lot of how the header is made. The ports being on opposite sides of the Subaru engine do not make things easy when designing a header for our cars. Each change in length during testing requires almost making a new header on a Subaru boxer motor, thus the rather lengthy design process of our header. Getting lengths equal is definitely a big task given the packaging, and any variance within .5-1" is considered the mark of a top notch header designer.
if anyone cares, from cobbtuning.com
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