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Motor vehicle exhaust noise – new regulation 2014

Posted on 25 Nov 2013 in Noise Patrol | 0 comments

Addendum 40: Regulation 41, Rev. 2

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Vehicle exhaust noise emission has been regulated for quite some time now, but with the beginning of 2014 the situation gets a bit tougher for the motor industry. The new tests outlined in the ECE/Trans/505/Rev.1/Add.40/Rev.2 are an upgrade to previous tests that seem more difficult. On the other hand, the tests are just better defined with more constraints making it more repeatable. It does leave less room for manufacturers to play with how the motorcycle sounds and not just how loud it is. In order to understand how exactly the new Directive will affect the motor vehicle industry, here is a list of tests to be performed:


    • Constant speed noise level test
    • Noise at Full throttle acceleration test
    • Noise from stationary vehicle



All three tests are equally important for compliance with standards, but the second one is more rigorous in terms of variables that are defined for the needed test. Formula (PMR) based on motor vehicle power and kerb weight define parameters for constant speed and full throttle tests.

Constant speed test is divided into two categories – 40 km/h and 50 km/h based on the formula mentioned above. This part of the test is very simple and the vehicle just needs to pass the measurement track with the required speed.

Full throttle acceleration test is much more complex in terms of practical execution. Following are the conditions that have to be met in order for measurement to be according to the new regulation:

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PMR based velocity categorisation: The velocity at which the vehicle passes the halfway line of the test track is either 40 km/h or 50 km/h. Velocity at which the motorcycle enters the test track is determined so that the motorcycle reaches prescribed velocity at the halfway point.
Reference and target acceleration: Based on the PMR, two categories for wide open throttle are formed. Each has a formula for calculation of wide open throttle acceleration that is based on the specific PMR of the vehicle. It is a calculation of target acceleration. Similarly, acceleration for urban driving is calculated using same formula but different coefficients..

Tests should be performed without gear changes. If a given gear cannot meet the conditions of acceleration within 10%, two gears are used (a gear with higher acceleration and the next gear with lower acceleration). If rated engine speed is exceeded in a gear before reaching the end of the track, a higher gear should be used. If a vehicle has more than one gear, a gear higher than the first should be used.

For automatic and CVT transmissions a gear shift into a higher gear and higher acceleration is allowed. It is permitted to introduce a device that prevent downshifts if they are not a typical part of normal operation for given conditions.

At least three measurements should be performed on each side of the vehicle and for each gear.

The last test is perhaps the simplest in terms of facilities and needed space. Vehicle should be put to neutral gear. During the test, engine hood needs to remain closed. In case of no neutral gear available, the test should be carried out with rear wheel raised from the ground. On the other hand, this test has a detailed procedure of measurements and durations that need to be fulfilled for the measurement to be correct. Requirements for the test are:
Prescribed RPM signature measurement where engine speed goes from idle, to either 50% or 75% engine speed and then back to idle. The procedure is crucial and can be very simple or quite complicated depending on the equipment used to control and monitor all the relevant parameters without opening the engine compartment. The stationary noise test takes the least time and preparation. It is a very good indicator for both tests where motorcycle is moving. The regulation will be in effect very soon and measurements will be crucial.

Noise Patrol puts fears to rest when it comes to measuring stationary exhaust noise which is at the same time first condition for any further measurements. With its advanced IntelliRevTM package for RPM acquisition, the system is now a complete all-in-one solution for stationary noise tests of motor vehicles.


The three tests are all mandatory for state approval of the vehicle to be used on public roads. And the fact that the first two tests are complicated because they evaluate the vehicle as a model for all subsequent vehicles of the same type. This makes the Stationary exhaust test even more relevant. Because that is the one that is in some countries even a requirement for passing the obligatory technical inspection. It is also used by police to quickly and efficiently determine the deviation from the original vehicle as is stated by the manufacturer.

Because these tests are performed consistently through the cycle of a motor vehicle speed and efficiency of such measurements is the key. And Noise Patrol is an all in one solution to perform measurements of stationary exhaust noise every day with ease and reliability.


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