ACEM

European Guidelines on Anti-Tampering Rules for Motorcycle Exhaust Silencers

In a press release dated May 31, 2023, the European Association of Motorcycle Manufacturers (ACEM) said that it "shares the concerns of citizens, politicians and regulators regarding the impact of noise in daily life" and that "sound emissions of motorcycles have been regulated in the EU, with maximum permitted levels defined since the 1990s, through European type approval requirements."

The release stated that "as part of the solution to address these concerns, ACEM has recently developed a set of guidelines in cooperation with key aftermarket exhaust industry players" and that "the aim of these guidelines is to avoid diverging, non-effective interpretations of anti-tampering rules for exhaust silencers, in particular for non-original equipment that may be alternatively fitted on motorcycles over their lifetime.  

At the time Antonio Perlot, ACEM Secretary General, was quoted as saying that "this initiative, bringing together the expertise of recognized players in the motorcycle sector, addresses one of the main causes of motorcycle noise in the streets. 

"Approved silencers with too easily removable baffles or dB-Killers are today still present on the market, which may result in unacceptably high levels of noise on the road.

"Putting forward state of the art solutions, the guidelines will help type approval authorities towards a more harmonized assessment of conformity to anti-tampering rules for exhaust silencers. The call is now on all stakeholders to apply them without delay."

For sound level and anti-tampering rules of motorcycle exhaust silencers, the EU type approval framework Regulation 168/2013 mandates the application of United Nations Economic Commission for Europe (UNECE) Regulations no. 92 (aftermarket silencers) and no. 41 (original motorcycle). 

These regulations were developed and are maintained by the Working Party Noise and Tyres (Groupe Rapporteur Bruit et Pneumatiques - GRBP), under the World Forum for the harmonisation of vehicle regulations (WP.29), operating within the UNECE.

In December 2022, ACEM presented the guidelines to national type approval authorities at a stakeholder meeting organized by the European Commission. Following an informal approval by authorities at EU level, the International Motorcycle Manufacturers' Association (IMMA) introduced the guidelines in February 2023 at GRBP, the world forum on sound level of vehicles. A final document is expected be adopted at the next GRBP session in September 2023.

This initiative has been jointly developed within the motorcycle sector, by ACEM, IMMA, and a selection of motorcycle exhaust manufacturers - Akrapovic, Arrow, Giannelli, Lafranconi, LeoVince, MIVV and SC-Project.

The guidelines clarify the technical requirements "to ensure robustness of fixing solutions for silencing baffles and dB-killers, to prevent their easy removal", and AMD is now able to present a light-touch edit of those guidelines. 

www.acem.eu

Guidelines

These are the key elements and recommendations contained in the IMMA Informal document (GRBP-77-20) submitted to the UNECE Working Party on Noise and Tyres (GRBP).

They form the proposed industry guidelines on the anti-tampering provisions for Non-Original Replacement Exhaust Systems (NORESS) - namely, aftermarket exhausts - in UN Regulation No. 92.

The aim of the guidelines is to support "manufacturers, national Type-Approval authorities and enforcement authorities in their understanding of the requirements under section 6.3.1 of UN Regulation No. 92."

The stated intention is to give guidance on the interpretation of the guidelines with a view to "provide NORESS manufacturers with regulatory certainty, to ensure the implementation of a high level of anti-tampering measures, and to provide national authorities with a set of harmonized best practices for these requirements."

The two key definitions in the guidelines concern:

• Baffle: the component or sub-assembly that contributes to the noise attenuation performance of a silencer, e.g. 'dB killer'.

• Tamper-proof: an exhaust is considered tamper-proof when grinding, cutting or drilling is required to remove an exit-cone, a fastener or a baffle from a silencer.

• Permanent and irrecoverable damages - "removal causing permanent/irrecoverable damage to the assembly" is understood as a being the result of using other mechanical means than traditional, low cost, easily available tools such as hammer, screwdrivers, or pliers.

• "Permanent/irrecoverable damage" includes damages to the aesthetics of the product or damages which would prevent the reintroduction of the removed part(s)."

'Photo: ACEM'

To avoid any uncertainty, the document is very specific in terms of the interpretation of anti-tampering:

• "The NORESS or its components shall be constructed in a way that does not permit removal of baffles, exit-cones and other parts whose primary function is as part of the silencing/expansion chambers.

• "Where incorporation of such a part is unavoidable, its method of attachment shall be such that removal is not facilitated (e.g. with conventional threaded fixings) and shall also be attached such that removal causes permanent/irrecoverable damage to the assembly.

• "Baffles and exit-cones should not be removable by construction/design. Exhaust manufacturers [must] therefore take the necessary means so that the NORESS integrity would not be easily compromized by users/owners.

• "Exit-cones should be tamper-proof. In detail, this means that conventional threaded fixing or similar methods used to fasten exit-cones to the rest of the assembly are not considered as tamper-proof.

• "Should manufacturers use conventional threaded fixing or similar, exit-cones should be also fastened to the exhaust casing by another method such as gluing or welding. Rivets (stainless steel, not aluminum) or break-head bolts may be used to secure exit-cones to the exhaust casing. Should manufacturers use non-stainless steel rivets, exit-cones should be also fastened to the exhaust casing by another method such as gluing or welding. Alternatively, exit-cone fasteners should be filled with epoxy or similar substance;

• "The baffles should be fixed to the exhaust casing or to the exit-cone so as to ensure that removal of the exit-cones should not facilitate the removal of the baffle. The baffle should be tamper-proof: examples of its fixing methods include sufficient welding or use of threaded fixings covered by epoxy or similar substances.

• "Cosmetic end caps (exit-cones) may be attached with conventional fasteners if removal of the end cap does not facilitate removal of baffles or attenuation devices, and is not a part whose function is as part of the silencing/expansion chambers.

• "Baffles and other parts should be welded to the exhaust (exit-cone or exhaust casing) as a primary method of attachment. It is the manufacturer's choice and responsibility to make sure that such welding covers a sufficient perimeter of the outer rim of the baffle to avoid easy removals.

• "Screws and other threaded fixings can be used as a secondary way to secure the baffle to the exhaust, or as an alternative to welding if welding is not technically possible due to different materials being used for the exit-cone and the exhaust casing, for example. In such cases, these fixings should be secured by welding, or filled with epoxy or similar substances.

• "Baffles should never be attached to the rest of the assembly by use of circlips or similar method of assembly as this would not be considered a tamper-proof method of attachment.

• "The NORESS or its components shall be constructed in a way that does not permit removal of baffles, exit-cones and other parts whose primary function is as part of the silencing/expansion chambers. 

• "Where incorporation of such a part is unavoidable, its method of attachment shall be such that removal is not facilitated (e.g. with conventional threaded fixings) and shall also be attached such that removal causes permanent/irrecoverable damage to the assembly."