Exhaust Group Buy RESONATOR description
Posted: Sat Apr 20, 2002 6:34 pm
I asked Russ what a resonator did and the effect on performance
Larry Witherspoon
Torrance (Los Angeles)
day/office phone 562-982-7720
larry.d.witherspoon@boeing.com
ssspoon@aol.com
Larry:
I used the term 'resonator' very loosely. A resonator, sometimes called a pre muffler, is included in an exhaust system to break up the sound a bit before it gets to the muffler so that the muffler will have an easier job, thus making it more effective. I am looking at using a smooth bore glasspack as a resonator. I won't go into a discussion on acoustic principles at this point because the subject is quite large and it is not within the scope of an email to do it justice.
In practical terms the reality is this: a resonator is there to assist the muffler but more importantly to alter the resonance frequency of the system. Anyone who has ever ridden in a car with a 'hot rod' exhaust system has noticed that the exhaust note always seems to drone unbearably at cruising speed/rpm. This drone is the result of the pulses in the exhaust at that specific rpm being timed to match the resonance frequency of the exhaust system thus amplifying the decibel level. In other words the sonic waves that are reflected up and down the length of the pipe are in time with the pulses that are coming from the exhaust ports. The resonator is there in an attempt to alter the resonance characteristics of the system and move the resonance frequency to a point that is hopefully outside the operating range of the engine.
Every system has different requirements for altering the resonance frequency in such a way that is desirable. Some systems may need no such resonator at all. Only careful testing will illustrate the effectiveness of any modification. Will the system that I am building for the Legacy require a resonator? I have no idea... but I don't see how it would hurt.
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Larry Witherspoon
Torrance (Los Angeles)
day/office phone 562-982-7720
larry.d.witherspoon@boeing.com
ssspoon@aol.com
Larry:
I used the term 'resonator' very loosely. A resonator, sometimes called a pre muffler, is included in an exhaust system to break up the sound a bit before it gets to the muffler so that the muffler will have an easier job, thus making it more effective. I am looking at using a smooth bore glasspack as a resonator. I won't go into a discussion on acoustic principles at this point because the subject is quite large and it is not within the scope of an email to do it justice.
In practical terms the reality is this: a resonator is there to assist the muffler but more importantly to alter the resonance frequency of the system. Anyone who has ever ridden in a car with a 'hot rod' exhaust system has noticed that the exhaust note always seems to drone unbearably at cruising speed/rpm. This drone is the result of the pulses in the exhaust at that specific rpm being timed to match the resonance frequency of the exhaust system thus amplifying the decibel level. In other words the sonic waves that are reflected up and down the length of the pipe are in time with the pulses that are coming from the exhaust ports. The resonator is there in an attempt to alter the resonance characteristics of the system and move the resonance frequency to a point that is hopefully outside the operating range of the engine.
Every system has different requirements for altering the resonance frequency in such a way that is desirable. Some systems may need no such resonator at all. Only careful testing will illustrate the effectiveness of any modification. Will the system that I am building for the Legacy require a resonator? I have no idea... but I don't see how it would hurt.
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