Euro5 emissions rules will bring tech progress

Diagram shows Euro5 compliant BMW S1000RR motor
Diagram shows Euro5 compliant BMW S1000RR motor

It isn’t hard to find naysayers preaching gloom about tightening emissions laws but the reality is that they tend to spur development, creating bikes that are measurably better than their predecessors.

The latest European limits are introduced from the start of next year and promise to bring another jolt of technological advancement.

What is Euro5?

It’ll come as no surprise to hear that Euro5 is the fifth iteration of European emissions limits that have got steadily stricter since the original Euro1 came in 1999.

The limits below illustrate the astounding improvements over the two decades since: compared to the current Euro4 limits, Euro5 levels are down by a third, a smaller change than from Euro3 to 4, but still a tough challenge.

The big news is the introduction of a limit for 'non- methane hydrocarbons' (NMHC) – quite literally hydrocarbons that aren’t methane – which wasn’t measured before. NMHC makes up most of a bike’s HC emissions, so the 0.068g/km limit is a particular challenge.

The emissions testing itself

As before, Euro5’s introduction is staged. New models from January 1, 2020 must meet the limits but manufacturers have an extra 12 months to adapt existing designs.

Brexit (let's not disappear down that rabbit hole) won’t exclude the UK from compliance – we’re already committed to remaining aligned with EU rules and other non-EU countries such as India and China are adopting similar standards.

High-rev hassles

High-revving performance engines are hit hardest by the new rules – just as they were by Euro4. They need long valve duration (the time valves are open) and lots of overlap (when exhaust and intake valves are both open) to perform at high revs.

But at low revs the same settings lead to lots of HC emissions, so we can expect to see an explosion in the use of variable valve timing: BMW’s Euro5-legal S1000RR lights the way. Far from dulling performance, VVT adds more.

The 2019 BMW S1000RR is Euro5 compliant

We’ll also see capacities stretched to boost performance and reduce reliance on high revs. Next year’s upsized Triumph Tiger 800, not to mention the existing 1103cc Ducati Panigale V4 and 1078cc Aprilia RSV4, show it’s already happening.

One downside to all this is that, while the bikes are getting more impressive, they’re also more complicated, making them more expensive to produce, and making maintenance more expensive in the long run.

Aprilia's RSV4 1100 Factory is evidence of increasing capacity

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