D
Deleted Member 4613
Guest
Question: Would a cvt on a 2 stroke reduce noise at high speed by down shifting? Normally, a 2 stroke makes too much noise when it winds out.
Mike S
Mike S
loquin
Well-Known Member
Whether a CVT is going to help with engine noise depends on whether you adjust your gearing to allow a higher speed. If you do, the engine will be running at a lower RPM at your cruise speed, assuming that you hold the cruise speed the same, before and after.
But, if you go faster (which we probably would all tend to do, if the speed is there!) then the engine will be back at its upper limit, and you won't reduce the noise any. You WILL be in the neighborhood for a shorter time. But, it'll probably still torque the neighbors!
But, if you go faster (which we probably would all tend to do, if the speed is there!) then the engine will be back at its upper limit, and you won't reduce the noise any. You WILL be in the neighborhood for a shorter time. But, it'll probably still torque the neighbors!
loquin
Well-Known Member
However...
You should end up running the engine more in the peak torque band. Keep in mind that exhaust systems are frequency (RPM) specific, and can be 'tuned' at various frequencies to reduce noise selectively at different frequencies. (they are actually a series of band-pass filters, and are typically designed with at least two, and often three or more chambers or sections, each of which allows noise at specific frequencies to pass more easily. (and this greatly reduces the sound output at other frequencies.) By placing one chamber after the next, and by having each chamber tuned to pass sound at a different than the others, you can get better sound reduction and better air flow than by attempting to muffle all frequencies equally.)
You can hear this as your engine ramps up through it's range. Here and there, as you spin up the engine, the sound appears louder than at others.
So, if your particular exhaust system is particularly good at muffling sound at the RPM at which you'll be spending the bulk of your time with the CVT, then the CVT will definitely be reducing the overall noise you generate.
If, however, the max-torque RPMs happen to fall on a part of the sound spectrum that your exhaust doesn't muffle as well, then a CVT could actually INCREASE the overall noise level, since your engine would be spending more time at that RPM than before.
You should end up running the engine more in the peak torque band. Keep in mind that exhaust systems are frequency (RPM) specific, and can be 'tuned' at various frequencies to reduce noise selectively at different frequencies. (they are actually a series of band-pass filters, and are typically designed with at least two, and often three or more chambers or sections, each of which allows noise at specific frequencies to pass more easily. (and this greatly reduces the sound output at other frequencies.) By placing one chamber after the next, and by having each chamber tuned to pass sound at a different than the others, you can get better sound reduction and better air flow than by attempting to muffle all frequencies equally.)
You can hear this as your engine ramps up through it's range. Here and there, as you spin up the engine, the sound appears louder than at others.
So, if your particular exhaust system is particularly good at muffling sound at the RPM at which you'll be spending the bulk of your time with the CVT, then the CVT will definitely be reducing the overall noise you generate.
If, however, the max-torque RPMs happen to fall on a part of the sound spectrum that your exhaust doesn't muffle as well, then a CVT could actually INCREASE the overall noise level, since your engine would be spending more time at that RPM than before.
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