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Author Topic: Best place to mount mufflers in your exhaust system  (Read 2065 times)

b00stinz

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Best place to mount mufflers in your exhaust system
« on: October 01, 2010, 12:02:21 PM »
Thank you to jaymanson of http://www.300zx.co.nz

LOCATION OF MUFFLERS IN AN EXHAUST SYSTEM

In many instances the question has been raised "Where is the best place to locate a muffler in an exhaust system?"

The Donaldson Company, makers of air cleaners and exhaust mufflers, completed an investigation to determine the effects of muffler location on its efficiency. Two factors must be considered in conjunction with muffler efficiency - first, exhaust restriction and second, silencing effect. The investigation definitely indicated that there is a direct relationship between muffler location and efficiency.

In order to more easily understand how a muffler location has an effect on its efficiency, we must have a background on what is happening inside the exhaust pipe. The pulse produced by each cylinder exhausting sets up a vibration termed a "standing wave". These are sound waves which are nearly independent of the exhaust gas flow. They are set up and kept in vibration by the exhaust impulses from the engine. They are directly dependent upon the exhaust system length, gas temperature and the frequency of the exhaust surges. The included sketch graphically illustrates the principles of the standing wave.





The exhaust pulses occur at a rate that make the areas of high and low pressures stationary. The sound has regions of minimum pressure change (nodes) and regions of maximum pressure change (anti-nodes). In the sketch the letter "N" locates the nodes and the letter "A" locates the anti-nodes.

Laboratory experiments were conducted using a 5ft long tube to simulate an exhaust system. It was found that anti-nodes constantly occurred at the source, at 2 ft and 4ft - Nodes on the other hand, occurred at 1 ft,3ft and 5ft. Further experiments indicated that anti-nodes occurred at 2/5 and 4/5 the system's length. Also, that mufflers were most effective when located at the anti-node points.

To more completely understand the 2/5 and 4/5 length principle, we will consider a typical exhaust system. The total length from manifold to outlet is 21 ft - to be included in this length is a 3ft muffler. The experiments indicated the best location for a muffler is at the exhaust ports (in most cases this is impossible). The next best location is at 2/5 the total length - the next is 4/5 the length. Therefore, the centre of the muffler should be located at 2/5 of the 21ft length or at 8.4ft. Subtract half the length of the muffler or 1.5ft and the exhaust pipe will be 6.9ft long and the tailpipe will be 11.1 ft long.

1. The most efficient location for the muffler is at the exhaust ports.
2. The 2nd best location is at 2/5 the total length of the system.
3. The 3rd best location is at 4/5 the total length of the system.
4. The worst location is at 1/5 or 3/5 the systems length or with the muffler at the outlet of the system.

It is not always possible to locate the muffler in the best location, however you should know where the best points are or at best try to avoid the worst location.

cefliner

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Best place to mount mufflers in your exhaust system
« Reply #1 on: July 18, 2011, 10:20:00 PM »
Do you know if this information applies in the same way for turbo cars?  Having an obstruction such as a turbo right off the manifold must change or smooth out the pulses that come from the engine.  Also do you know the correlation between exhaust diameter vs pulse/sound wave length (if there is any)?  A good little read.

Zanthiath

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Best place to mount mufflers in your exhaust system
« Reply #2 on: July 19, 2011, 08:24:46 PM »
Its called QTP for performance and good quality mufflers for cruising

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