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One point that is always a topic of discussion is the clearly perceptible, low-frequency drone of both GS, which is particularly noticeable in part-load and full-load operation at speeds between 80 and 130 km/h. However, this is exactly the speed range in which most riders ride on the road. Or the range you can avoid the least. Some riders report that the noise can cause discomfort on longer trips.

This was the reason for the developers at Wunderlich to investigate the phenomenon – which they knew from their own experience – in engineering terms, in order to subsequently develop a functional solution that reduces and minimizes the effect.

The phenomenon and its cause

During test rides, BMW specialists were able to identify the resonance chamber, which is roughly formed by the inside of the cases and the entire rear wheel arch, as the source of the noise. The right mounted muffler also protrudes into this space. The resonance chamber turns out to be the sound source because of its geometry, volume and the materials (and their acoustic reflection behavior) that bound it. Accordingly, it is not primarily mechanical vibrations but rather the sound pressure escaping directly from the exhaust that stimulates the described chamber to resonate. This resonance chamber acts like a mechanical amplifier. It is the cause of the booming noise.

After this realization, it was also clear why the noise was particularly noticeable in the partial-load and full-load ranges: these are the operating conditions in which the sound pressure level of the exhaust is physically at its highest.

The aim was therefore to eliminate the resonance chamber described above as the source of the noise. This could only be achieved if the sound pressure and the exhaust gas flow from the muffler were diverted or deflected. A conventional sound insulation was ruled out at Wunderlich – because it was not practicable.

Wunderlich exhaust deflector »GONZZOO«

With this knowledge in mind, the developers considered a deflector solution right from the start. The deflector had to be designed to deflect or shield the sound pressure in a targeted manner so that it would not reach the resonance chamber at all and cause it to drone. This defined the primary requirements of the specifications:

• The redirection of the sound pressure was to ensure significant noise reduction at head heightof the rider and passenger.
• The shielding upwards and to the side was to have the additional positive effect that the sound waves are radiated downwards and to the rear and are therefore perceived as less loud.
• In the subjective perception when passing the GS, a significant noise reduction should be achieved – depending on the free field conditions.
• The deflector should shield the heat radiation of the exhaust gas stream in such a way that the heating of the right-hand case and the case contents is noticeably reduced.

In addition to the challenges posed by the demanding primary requirements, the Wunderlich developers paid particular attention to further general conditions. After all, only those who unprofessionally manipulate the exhaust system risk invalidating the operating permit. For this reason, Wunderlich‘s specifications included further technical requirements of essential importance:

• The exhaust deflector should recieve a type approval certificate (EEC).
•  The solution should not affect the engine performance, especially not negatively, i.e. it should not change the backpressure in the exhaust system compared to the series production.
• The solution should be simple and effective, especially when riding with mounted cases.
• The solution should be flexible and small in terms of geometry.

With the now presented exhaust deflector »GONZZOO« Wunderlich has fulfilled all mentioned requirements. It is model specific designed, to fit the BMW R 1250 GS + Adventure as well as the BMW R 1200 GS LC + Adventure.

The »GONZZOO« – efficient, ingeniously designed and with type approval certificate (EEC)

The Wunderlich deflector »GONZZOO« efficiently reduces the specific drone of the GS described above. And it reduces the noise pollution for the environment. Thus, it complies with the in-house sustainability initiative Wunderlich BLUE. The »GONZZOO« is remarkable because Wunderlich has managed to reduce it to the bare essentials at the same time. In doing so, it is easy to misjudge the physical and engineering know-how that goes into it. After all, the extensive preliminary tests for the development of the effective deflector were time-consuming.

TÜV Rheinland (German Technical Inspection Association) carried out its own series of measurements on the deflector following the Ringener measurements as part of the technical tests for the granting of the type approval certificate (EEC). These extensive measurements prove that the limit values of the sound pressure levels of the original exhaust system are not changed. The completion of the administrative act at the German Federal Motor Transport Authority, which concludes the official granting of the type approval certificate (EEC) for the BMW R 1250 GS (incl. Adventure) and the BMW R 1200 GS LC (incl. Adventure), is expected soon.

Always ready for action: the »GONZZOO« is compact and easy to stow away

A big advantage is that the »GONZZOO« is small and easy to stow away and always have with you. So you can mount or dismount it on the road at any time thanks to the spring clamps and use it flexibly everywhere (Slip-on)!

Wunderlich manufactures the exhaust deflector »GONZZOO« in Germany and offers it from February for all BMW R 1200 GS LC and the R 1250 GS models at a price of 79.90 €*.

*The price may vary from country to country.

At a glance:

Item-no.:
20881-000 – Wunderlich »GONZZOO« exhaust deflector – stainless steel

Function
• Suitable for BMW R 1250 GS + Adventure as well as R 1200 GS LC + Adventure with original muffler
• The »GONZZOO« exhaust deflector provides significant noise reduction at head level for rider and passenger and minimizes the drone of the GS, which is often perceived as unpleasant
• Less noise results in a more relaxed and safer ride
• No loss of power
• In terms of subjective perception, there is a significant reduction in noise when the GS passes by – depending on the open-air conditions
• Shields the cases from the heat radiation of the exhaust stream and reduces heating of the contents
• Compact, effective design
• Easy to stow
• Precisely fitting, secure, simple installation with spring hooks (Slip-on)
• Mounting tool included
• Type approval certificate (EEC) in preparation

Technical data
• Material: stainless steel, precisely processed

Special features
•  Wunderlich premium product.
• Small series. Handmade
• Design. Functional and integrated.
• 60 days return policy
• Made in Germany
• 5 years warranty

Is there a connection between noise reduction and ergonomics?

Perception and its effects on safety

When riding a motorcycle, nothing should irritate and thus distract from joyful riding and traffic events. Wunderlich offers a huge range of ergonomic components that take precisely this approach. They allow to adapted the motorcycle in such a way that nothing irritates or disturbs and you can enjoy riding, but also anticipate traffic situations, because all man-machine interfaces fit perfectly. Ergonomics therefore not only creates a gain in comfort and riding pleasure, but – actually just as relevant – an extra level of safety when riding a motorcycle.
What applies to an unergonomic motorcycle in the conventional sense can also be applied to noise pollution. In addition to the purely objective stress, noise pollution can cause subjectively perceived impairments to well-being, which irritate and disturb while riding, so that the rider can no longer concentrate 100% on riding and the traffic situation. Reducing noise pollution and the associated subjective impairment of well-being also improves riding safety and, above all, riding pleasure.

Web links:
Wunderlich »GONZZOO« exhaust deflector
www.wunderlich.de/en
www.wunderlich.app