New exhaust & noise regulations for motorcycles from 2025: will they be quieter?

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The Euro 5 emissions standard brought a flood of new requirements for motorcycle manufacturers. As the Euro 5 standard was tailored to cars, the EU signaled early on that adjustments were to be expected for application to two-wheelers. The adjustments came relatively late in relation to typical vehicle development cycles, namely in 2019 and 2020, shortly before Euro 5 was due to apply to motorcycles from the beginning of 2020.

For many experts, the area in which the EU wanted to make concessions was also unexpected: exhaust emissions, of all things. Few would have expected this after the huge publicity surrounding Volkswagen's emissions scandal. The limit values for pollutants have been retained, but the difficult task of proving the durability of exhaust gas aftertreatment has been postponed until 2025, to the Euro 5+ standard, as it is now called.

At the same time, new regulations on noise measurement will apply from January 1, 2025, namely those in accordance with UNECE R41.05. The limit values do not change compared to the previously applied R41.04, but they must be achieved under significantly more operating conditions. We talked to Dr. Frank Schwarz, who heads the Thermodynamics/Function/Emissions department at BMW Motorrad. He explained the technology and the significance of the regulations for the new vehicles in customer hands.

The new

With the Euro 5 standard (without Plus), which has been in force since 2020, manufacturers were still allowed to prove durability using a relatively simple procedure. For motorcycle models with a maximum design speed of over 130 km/h, a homologation model drove 3500 km, i.e. 10 percent of the distance of 35,000 km specified by the EU as "durability" for motorcycles. Here, the values had to be 30 percent better than prescribed in the standard in the expectation of a linear degradation over the remaining 90 percent of the driving distance.

What is new for Euro 5+ is that this extrapolation is no longer sufficient. Stronger proof of durability must be provided. Manufacturers can, for example, complete the entire 35,000 km on a test bench in a specified measurement cycle and measure the results. However, they may also measure half of the distance and derive the second half from the measurement results. As the catalytic converter primarily ages thermally, manufacturers can alternatively use the same methods of thermal ageing of the catalytic converter as are commonly used in the passenger car sector. The catalytic converter artificially aged in this way is installed in the test vehicle, which is then measured. If the exhaust emission values are still correct, the model can be approved.

Onboard diagnostics of the emission control system

The catalytic converter was also added to the onboard diagnostics and logging obligations for Euro 5+. In order to check the function of the catalytic converter during operation, two lambda sensors are used, one upstream of the catalytic converter and one downstream. Since it was not known for so long what exactly would be postponed from the Euro 5 specifications and what the scope would be, there were already many models with two sensors in 2020. At BMW Motorrad, for example, these were the flagship GS and the four-cylinder models. From a purely technical point of view, these motorcycles could have been homologated as Euro 5+ back then, but this was not possible under EU law as the specifications were not yet final.

In catalytic converter diagnostics, the two lambda sensors monitor the oxygen content of the exhaust gas in the context of various engine operating states. The catalytic converter stores oxygen. If the engine is running rich, i.e. with excess fuel and too little oxygen, the catalytic converter releases oxygen. If the engine is running lean, i.e. with excess air, the catalytic converter stores oxygen. The two probes measure the values before and after the catalytic converter. Together with data on the exhaust gas flow, the engine control unit uses this to calculate the oxygen behavior of the catalytic converter. The condition of the component can be determined from this data because the oxygen behavior correlates with the complete catalytic converter effect.

Engine indicator light and official check

The user in the saddle is primarily informed of faults during operation via the engine warning light. Although the exhaust gas limit values for Euro 5+ remain basically the same as for Euro 5, the onboard diagnostics must switch on the engine warning light in the event of significantly smaller deviations during operation. This applies to the values for unburned hydrocarbons, carbon monoxide and nitrogen oxides. "Of course, customers should not see the warning light more frequently in vehicles approved to Euro 5+ than in earlier models," says Dr. Frank Schwarz. "That's why we design the system to be correspondingly robust."

The engine control unit logs the data collected for the functional diagnostics. The workshop reads it out during servicing and the manufacturers transmit the data to the Federal Motor Transport Authority (KBA). The authority thus receives evidence of the correct behavior of the diagnostics in regular vehicle operation.

Noise regulations: 0.01 more

The UNECE R41.05 regulation for noise emissions applies at the same time as Euro 5+ for exhaust emissions. It replaces UNECE R41.04, which was introduced in 2016 with Euro 4. The limit values do not change here either. Why no stricter limits? The motorcycle association ACEM answered this question in the form of a measurement with a BMW R 1250 GS. If the machine is completely encapsulated, i.e. only rolling noises reach the microphones, this is almost as loud as the same machine with engine noise when passing at 50 km/h – and we are dealing with a cardan motorcycle here. Energica's e-motorcycles show how loud the drive chain alone can be. So it's the same as with other vehicles: the main noise eventually comes from rolling. The ACEM therefore campaigned for the limit values not to be lowered any further.

Instead, more operating conditions are checked within the "Additional Sound Emission Provisions" (ASEP). They were introduced with R41.04 for new registrations from 2016 and apply to around 80 percent of motorcycles registered in Germany (Class III). R41.05 expands the ASEP considerably. From 2025, the ASEP limit value curves must be complied with up to 80 percent of the maximum engine speed and in the speed range 10 to 100 km/h. Measurements will also be taken in all gears.

Are the motorcycles getting quieter?

"Nothing changes in the operating states in which measurements have already been taken," answers Frank Schwarz. "However, most motorcycles become quieter in the areas where no measurements were taken beforehand. The R41.03 was still very focused on the 'accelerating on the outskirts' scenario; the R41.04 was very focused on scenarios in urban areas. The new procedure covers other parts, such as the majority of all driving areas in country road operation." This increases the workload considerably. There are around three to four times as many measuring points as before. Frank Schwarz checks his laptop: "In this measurement, for example, we previously had five measuring points. Now there are 20."

Additional checks

Another disadvantage of R41.04 was that the manufacturers measured themselves until November 2019 and certified their correctness. The authorities were supposed to re-measure a random sample from ongoing production. Since November 2019, an independent technical service provider (i.e. TÜV or Dekra in Germany) has been measuring for homologation. This process is retained in R41.05. Exceedances are detected earlier in the process.

The new volume regulations will therefore ensure lower engine noise emissions in the usual country road areas. Both the association and the manufacturers have endeavored to find a sustainable, social solution. Now the drivers and accessory manufacturers must also join in.

(cgl)