Engine development experts Ricardo explain the challenges of Euro5+ emissions regulations

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Back in February, it was announced that the Yamaha R1 superbike would be going track-only in Europe from 2025 – having made the decision not to update the 197bhp, 998cc four-cylinder engine to meet tougher Euro5+ regulations.

Arriving for 2024, Euro5+ is the latest in a long line of ever-increasing emissions rules that began back in 1999. Bikes already confirmed as conforming include the BMW R1300GS (pictured below), with more still to make the transition.

Building on Euro5, which came into effect in 2020, the new regs revolve around the deterioration of a motorcycle’s catalyst (elements in the exhaust to reduce emissions) during its lifespan, and pollution levels likely to be produced by a bike at the end of its life.  

BMW R1300GS cross section

Tests are required to assess the cat’s effectiveness over time and there’s now a need for mandatory monitoring through the bike’s Electronic Control Unit (ECU).

This calculates efficiency using an additional oxygen sensor placed after the catalyst. This data is then compared with the one placed before the catalyst and if there’s anything wrong, a Malfunction Indicator Lamp (MIL) will light up on the dash to let you know.

What does it all mean?

To find out more about Euro5+, MCN spoke with Walther Leardini and Paul Etheridge from Ricardo’s motorcycle team. Ricardo are a global strategic, environmental and engineering consulting company with over 100 years of engineering experience.

Four cylinder Suzuki engine cross section diagram

They employ close to 3000 people in over 20 countries – with operations including future propulsion technology in the motorcycle, automotive, marine and aerospace industries. They began consulting with motorcycle firms on Euro5 back in 2012.

“Catalysts perform well at high temperature, but there is a limit – go beyond that limit and a catalyst will destroy itself very quickly,” said Etheridge.

He has been with Ricardo for more than 40 years and was one of the founding members of their motorcycle division. He has an engineering background and has worked as project leader and chief engineer for many projects, including BMW’s six-cylinder engine found in the K1600.

A motorcycle in development at Ricardo

“You only need a few misfires from the engine and your catalyst will thermally run away because of that,” he said. “In addition to making sure the catalyst system is robust, you’ve got to make sure your whole engine is robust.”

In order to calculate whether a catalyser will stand the test of time, companies like Ricardo are able to simulate the life cycle of a motorcycle using specialist ovens.

A temperature of around 300° Celsius is needed to get the catalytic converter to begin working and there are tests for the speed of ‘light off’ (the minimum temperature required to commence the reaction) from a cold start. If the system is not capable of reaching the light off temperature quickly enough, the engine will fail the homologation test almost immediately.

Ricardo building signage

Challenging times

“As emissions legislation plays a larger part in motorcycle design and development, it is necessary to move the catalysts further and further forward towards the engine to ensure fast light off from a cold start, which requires a full system approach to design, engineering and vehicle integration,” Ricardo’s Etheridge continued.

“Deterioration of the catalyst can be due to poisoning,” Walther added – having developed the Euro5 model strategy for Piaggio Group in a previous life. “For example, oil from the engine that goes unburned into the catalyst and reduces its efficiency.”

Once the cat starts to fail, a warning light will come on and in an ideal world the rider should go to a dealer and have the system replaced. Just ignoring it could cause an MoT failure.