Harley-Davidson Insurance 2024

Revolutionary technology for the ultimate driving pleasure: Dr. Jekill & Mr. Hyde and the sound of the future

Content overview:

Almost everyone who thinks of Harley-Davidson thinks of the unmistakable sound of these machines. And although many love this sound more than anything else in the world, every few years it becomes more difficult for the motorcyclist to enjoy this sound.

Jekill and Hyde Street Glide Sharkskin Blue
Jekill and Hyde Street Glide Sharkskin Blue

With new rules and regulations, the best thing we can do is cruise along the highway quietly like a mouse without our beloved blubber as a suitable soundtrack. 

Valve exhaust manufacturer Dr. Jekill & Mr. Hyde offers the solution to thousands of drivers with their electronically adjustable exhaust systems, giving drivers the optimal sound without the risk of ending up on the wrong side of the law.

But with new agreements like R41.05 and Euro5+, the voices are getting louder and louder that flap exhaust systems are now over... but is that really the case? 

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Euro5+ and R41.05 - what does that mean?

First the facts: What do the new regulations mean?
Of course there are pages full of technical language written about it, but we'll summarize it briefly. Euro5+ is the current regulation for emissions controls and requires vehicles to meet strict criteria for harmful emissions. These provisions are essential to reduce environmental impacts and promote a more sustainable future; Criteria already outlined by Dr. Jekill & Mr. Hyde are fulfilled.

R41.05 is different because it concerns the noise regulation of motorcycles and is intended to reduce noise pollution. These regulations require that motorcycles remain below a certain decibel level at speeds between 10 and 100 km/h. These regulations apply to new motorcycles in the EU, as well as to previously registered motorcycles that are newly registered.

Dr. Jekill & Mr. Hyde offers the solution to stricter legislation

In order to write a program under these conditions that still offers the driver the ideal sound and is legal, a system must go through countless test runs and drives in order to perfectly match the software to the exhaust system. In short: it is almost impossible for a human being made of flesh and blood to achieve this.

Introducing Sabrina

To ensure that the new Dr. To ensure that Jekill & Mr. Hyde systems comply with R41.05 regulations, the exhaust manufacturer, headquartered in the Netherlands, has invested in a state-of-the-art testing laboratory. In a closed room with several microphones and the latest sound software, all bikes and their exhaust systems are tested and checked to the utmost.

Harley Factory Group 2022
a motorcycle in a room
The new CVO 121 Street Glide in the Jekill & Hyde test laboratory.

At the center of this testing process is a robot named Sabrina. It continuously carries out emission and sound measurements as well as endurance tests under the highest precision conditions. Thanks to it, a revolutionary flap system could be developed that adapts to driving behavior to maintain the optimal sound level and offer a constant sound experience within legal limits.


For this purpose, a completely new Smartbox (the brain of a Dr. Jekill & Mr. Hyde system) was developed, as well as servomotors that react at lightning speed. Since the software now has to intervene more often, this should not be perceived as a nuisance for the driver. Thanks to the new actuators, the flap can now be positioned in many more positions than before, so the ride still feels very 'smooth'.  

Without these testing facilities and technologies, it would be virtually impossible to develop a legal exhaust that both meets R41.05 standards and offers a high quality sound experience. Therefore, Dr. Jekill & Mr. Hyde is the only manufacturer of adjustable exhaust systems in the world that can provide the optimal sound through this combination of advanced technology, robotics and state-of-the-art testing infrastructure.

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New exhaust system for Harley-Davidson CVO 121 models

CVO 121 Harley-Davidson with Jekill and Hyde flap exhaust system
CVO 121 Harley-Davidson with Jekill and Hyde flap exhaust system

Thanks to the new technology and Sabrina, it's Dr. Jekill & Mr. Hyde managed to create a perfectly fitting exhaust for the new HD CVO 121 models. Which is of course legal and, despite new strict rules, still offers the driver the ultimate driving experience.

This technology is of course also used for all other new models such as the 117 Tourer, Sportster S and Nightster , making Dr. Jekill & Mr. Hyde more than ready for the future. So if you thought it was the end of the flap exhaust... you thought wrong!

Text & image credit: Dr. Jekill & Mr Hyde  


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