Silencer Construction and Homologation Requirements
. By Bikeland Staff
Following a consultation period with silencer manufacturers active in Track Racing, the FIM
announce the following new construction requirements for silencers in Track Racing (for all
500cc and 250cc single cylinder engines running on methanol).
• All silencers used must be homologated by the FIM.
• The FIM silencer homologation consists of several sound tests. Every sound test will be made
by using a conventional exhaust pipe and a modified exhaust pipe (see description in Nr 1).
Sound tests will be made with the FIM nominated official.
1. Exhaust pipe
A single main exhaust pipe, maximum 50 mm external diameter is prescribed. An exhaust pipe
may include external or internal sound suppression systems to reduce the sound level. Material
is free.
(Requirements to fix the exhaust pipe remain the unchanged).
2. Silencer construction
The silencer must be made as one complete, sealed unit without any removable parts.
The silencer must be a mechanical type, using the position of permanently fixed pipes, baffles
or plates to reduce the sound to the maximum permitted sound level.
Insulating material, for the sole purpose of reducing the external temperature of the silencer
body, is permitted provided it is contained within a sealed chamber that has no contact with
exhaust gas or the outside atmosphere.
The end of the silencer exhaust pipe, when fitted on the motorcycle, must remain horizontal
and parallel to the central axis of the machine (max. tolerance: +/- 10°). The maximum length
is 20 mm (including a rounded collar); the maximum internal diameter of the pipe exit is 45
mm (+ 2.0 mm tolerance). The end of the silencer must finish at a right angle and contain a
rounded collar (min. 5mm/max. 10 mm).
Fixing points to attach a heat shield must be included.
3. Silencer length and location
The position of the silencer is provided by the following limitations: the silencer/exhaust
system shall not exceed the leading edge of the rear wheel when viewed from the side and
leave space for the riders’ foot. The silencer exit is behind the rider and within the rear tyre
silhouette of the motorcycle when viewed from the side.
4. Maximum permitted sound level
A homologated silencer may not exceed the maximum permitted sound level of 112 dB/A + 3
dB/A (within the values for the precision of the method, i.e. all tolerance values included). A
Class 1/Type 1 sound meter is prescribed to make the sound tests.
Sound tests will be performed using the ‘2 meter max’ method (see Art.01.79), with an
adjusted maximum engine RPM for this application.
5. Engine RPM
All silencers presented for homologation will be tested with an engine RPM level of 11.500 rpm
to test the sound limit produced by the combination of the exhaust and silencer (rpm level to
be confirmed).
6. Period of validity
The new FIM homologated silencer will be required as from 01/01/2015. The period of
homologation is 5 years (as long as the silencer remains original).
Any new FIM homologated silencer shall be constructed according to these requirements and be
within the maximum permitted sound level. A homologation fee will be applied.