http://www.stealthcharger.com/index.asp

630-584-2170

John C. Ziehl


Owned and operated by John Ziehl, "Vicious Cycle Performance" is an engine building machine shop that has suspended operations to introduce Mr. Ziehl's "Pulse Charger Exhaust System". This revolutionary ATV exhaust system has "turned the ATV Performance world on its ear"… Literally!

I volunteered to test a Pulse Charger (PC) against my Yoshimura RS-3, and Mr. Ziehl took me up on my offer. Once again, I scheduled time with the local performance shop SandTrax of Tulsa, Oklahoma; where Lonnie tested both pipe brands in their "open" and "quiet" configurations. The dynamometer graphs, presented in an overlay of three consecutive runs (below), validates Vicious Cycle Performance's place in the "Performance Exhaust Arena".

Installation Observations:
The "form, fit, and feel" of the PC is top quality with a very shiny stainless steel "stepped header with megaphone" leading to the muffler. The muffler section is held together with stainless-steel screws for ease of maintenance. Installation is a breeze compared to some other exhaust systems, no struggling with too-long headers, or dealing with messy glues! I found it easy to install the muffler section if the front bolt is "started" first, then position the clamp.

The Pulse Charger exhaust system with its quiet insert is referred to as a "Stealth Charger" (SC)… a "quiet performance exhaust system" that does not produce the raspy "bark" that many four stroke exhausts emit. . I recorded the "exhaust noise" and performed an "audio spectrum analysis" to help explain why the SC, while making more exhaust noise than a stock pipe, is not as annoying to most people.

Additionally, I hope to enlighten Z400 Central members and visitors (with the help of audio spectrum graphs, sound pressure level readings, and human reaction to irritating noise studies) how the "perceived" noise of the SC is not overly annoying to most people.




A brief tutorial in perceived noise to humans: from Bruel & Kjaer's "Measuring Sound" (links found below)

"We have already defined sound as any pressure variation which can be heard by a human ear. This means a range of frequencies from 20 Hz to 20 kHz for a young,
healthy human ear. In terms of sound pressure level, audible sounds range from the threshold of hearing at 0 dB to the threshold of pain which can be over 130 dB.

Although an increase of 6 dB represents a doubling of the sound pressure, an increase of about 10 dB is required before the sound subjectively appears to be twice as loud. (The smallest change we can hear is about 3 dB).

The subjective or perceived loudness of a sound is determined by several complex factors. One such factor is that the human ear is not equally sensitive at all frequencies. It is most sensitive to sounds between 2 kHz and 5 kHz, and less sensitive at higher and lower frequencies." (left picture below)




Nowdays the "A" weighting network is the most widely used since the "B" and "C" weightings do not correlate well with subjective tests. One reason for this lack of correlation between subjective tests and "B" and "C" weighted measurements is because the equal loudness contours were based on experiments which used pure tones — and most common sounds are not pure tones, but very complex signals made up of many different tones. ( "A" weighted curve in above right picture)


Please Reference:Brüel & Kjær's Primers. We hope that they will provide you with a good introduction to subjects relevant to sound and vibration measurement.
http://www.bksv.com/2148.asp

Measuring Sound:
Answers some of the basic questions asked by the newcomer to a noise measuring programme.
http://www.bksv.com/pdf/Measuring_Sound.pdf

Sound Intensity:
Explains the fundamentals of sound intensity measurement. Both theory and applications are covered. Although intended as a basic introduction, some knowledge of sound pressure measurement is assumed.
http://www.bksv.com/pdf/Sound_Intensity.pdf


This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of either the World Health Organization or the United Nations Environment Programme
http://www.inchem.org/documents/ehc/ehc/ehc012.htm

1.1.3. Effects of noise:
3.2. Interference with communication:
3.5. Nonspecific effects:
3.7. Annoyance:
3.8. Effects on task performance:

Very good report

Alot of info you rounded up there...Good Job