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Stinger
With the body of a pipe shaped like the abdomen of a Bee, the stinger is aptly named. It creates a calibrated bleed down of exhaust pressure to maintain a control of the density inside the pipe. If the density changes too much throughout the desired RPM range, the pipe becomes less effective. Stinger design is a balance between maintaining the lowest pressure yet most consistent density throughout the cycle.

Silencer (Not Shown)
Complimenting the effect of the stinger, the silence both attenuates the sound and helps maintain backpressure. It also provides some attenuation of sonic waves that may resonate to nullify useful sonic waves.

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Silencers can have an effect on the scavenging action as well as attenuation to sonic waves reverberating from the divergent cones. A ?loosely packed? silencer will tend to have a lesser effect on cancellation of reverberations. Sometimes these reverberations show up on dyno runs as slight drops in torque at specific RPMs. This all depends on the pipe, but in some cases when a drop occurs on the dyno, it can sometimes be traced back to these reverberations. The silencer imparts a restriction on the exhaust. This restriction will maintain some backpressure in conjunction with the stinger. To a point, more pressure will maintain more heat, enabling the sonic waves to increase velocity with RPM. That?s a good thing as the shorter time period for between pulse cycles is optimized. The downside is that increased backpressure will begin to work against the negative pressure wave at some point. In addition, the exhaust is pulsing though the silencer, which allows it to breathe into the packing somewhat. The packing literally acts as a pressure reservoir. Changes to silencers are not always predictable. In some cases using different packing materials can add or take away power. Packing comes in various grades of fiberglass and steel wool. Basically a tighter packing will provide more of a reservoir effect to balance pressure for a longer period of time, but with less load leveling affect. This leads to increased bottom end, a wider power band, but a sharper top power band drop-off. The packing for some silencers can also be shortened. This adds to the sound level but can actually improve both bottom end and top end performance in some cases. The length of the silencer also has an effect. A longer silencer tends to add more heat at higher RPM extending the range. But a longer silencer has its limits as it can also affect the bottom range adversely. The best thing to do is test the silencers you have with various packing to see what works best with your configuration. Some of the top motor builders do this, but its seldom revealed.

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