The truth about Euro 4


Euro 4 is more than just about noise...

Euro 4 is the name of European legislation that

  • limits pollutants in the exhaust emissions of new vehicles,
  • limits how much fuel is allowed to evaporate from new vehicles, even at standstill,
  • describes how far into their life they should comply with these limits, and
  • limits how noisy they can be.

Euro 4 applies to all mass-produced vehicles sold Europe-wide, and manufacturers are forced by law to comply. Although, as a European directive, it only describes the limits and measurement techniques, not the actual method of limiting – so Eurocrats aren’t telling manufacturers how to limit exhaust emissions, just by how much. And it isn’t a standard standard – it differentiates between different types of vehicle by engine type and size. Motorcycle manufacturers get off relatively lightly; the emissions limits for cars, vans and trucks are far more draconian than for bikes. But that’s okay because there are more of them and we don’t care anyway.

So, as far as bikes are concerned, Euro 4 (which, for bikes, came into force this year) is contained within a wider European directive going by the sexy name of Regulation (EU) No 168/2013. This sets out the requirements for new bike approval; certain dimensional standards (number plate sizes etc), safety features (like ABS), and the importers and manufacturers’ responsibilities and obligations to me and you. Many of the specific Euro 4 requirements are contained in further standards only cross referenced in Regulation (EU) No 168/2013, which makes tracking down the standards and test methods something of a paper trail. Almost as if it was meant to be that way.

The broad idea of Euro 4 is that engines are noisy and dirty, and need their noise and emissions controlling to ensure we don’t completely contaminate the planet’s atmosphere with a howling, carcinogenic soup-fug (some people think limiting pollutants like this is the same as choosing to jump from the 40th floor of a skyscraper instead of the 20th – it might take longer, but you reach the same conclusion in the end). Anyway, to that end Euro 4’s controls are, unsurprisingly, harder to achieve than Euro 3, but not as tough as Euro 5 (which will be with us in 2020).

How do manufacturers beat Euro 4?

Manufacturers don’t beat Euro 4. They are legally bound to comply with it. They might cock it up sometimes and sail too close to the wind – Ducati sportsbikes are suspiciously loud (and even they’ve had the quieteners put on the new 959, with its shotgun exhaust getting it through noise regs – which haven’t changed for years, incidentally, so either the 959 is a noisier engine or they’re running out of room for the catalyst and other anti-emissions gubbins). And many manufacturers, including Ducati and Aprilia, incorporated a noise-defeating flap in the exhaust of their bikes which activated at suspiciously convenient revs for the drive-by part of the European noise-test.

But, on the whole, manufacturers play ball with Euro 4 – certainly on the emissions side of the legislation. The consequences of not doing so would be VW-sized catastrophe.

So how do manufacturers comply with Euro 4?

By doing what it asks – making engines clean and quiet – through diligent engineering. This means, for example, being parsimonious with fuel. In the slap-dash old days of carbs, engineers could use fuel to do things other than power an engine; they could keep temperatures down with it, they could use it to smooth transitions between throttle positions – it meant they wasted a lot of it straight into the exhaust, but that’s what backfiring was for. Today they can’t be as free and easy with fuel because their engine wouldn’t pass Euro regs. Hence they need the precision and control of fuel injection, and the battery of electronic sensors and systems to monitor it. And even then, they still need a catalytic converter in the exhaust to chemically convert the burned (and unburned) exhaust toxins to less harmful substances. At least it helps keep exhaust noise down.

The need for clean-running motors has led, as in the car world, to gaining complete control of engine management. Instead of, broadly, letting an engine do what it does, electronics have given engineers mastery of an engine’s behaviour and can monitor and adjust multiple aspects to keep it within emissions tolerances – the timing and quantity of fuelling, ignition timing, real-time tuning of intake and exhaust dimensions, even now, on Ducati’s Multistrada and XDiavel, intake and exhaust variable valve timing control.


And, furthermore, electronics are also used to monitor the running status of emissions controls, so that an engine built today will still have to be Euro 4 compliant after, currently, 20,000km (this will become the bike’s lifetime in Euro 5, with onboard systems needed to keep itself adjusted).

It’s a tough job, etc

People often assume engine designers must get frustrated by being asked to make their engines super-efficient or super-powerful, then told to plug them up with a catalytic converter, and make them whisper-quiet too. But that’s a misunderstanding of what an engine designer does. As soon as he or she sits down with a pencil and starts to design an engine, they start to compromise. When the marketing department tells them their engine has to look aircooled, even though the temperature control required to pass emissions (and noise) limits means it has to be watercooled, they don’t throw their toys out and get into raging arguments about it. Working out how to do it is the job, and the problems are every bit as taxing, the solutions as ingenious, and the results as satisfying, as finding an extra 0.2bhp at 13,500rpm (although they like the sexy stuff too). So when Brussels tells them they have to convert petrol and air, via combustion, into fragrant pixie dust and holy water vapour, while the marketing department are telling them the engine has to make 200bhp at 45mpg, and it has to last for 20,000 miles between services, and it has to be assembled by semi-skilled part-time workers in a factory in a developing nation... then that’s the job.

You could even argue, convincingly, that Euro regs are good for motorcycling (let alone the planet, etc). They’ve forced engineers to dig deep to come up with novel methods of cheating. No, sorry, I meant ‘making their engines more efficient, and even safer’. For example, no-one has noticed how sportsbike engines are becoming less powerful, despite Euro regs, because they aren’t. Between 2000 and 2015, litre sportsbikes gained 44% more peak power, from an early Yamaha R1’s 135bhp to a BMW S1000RR’s 195bhp. In the same time period they’ve gone from carbs to fuel injection, wire throttle cables to fly-by-wire, limiting power in lower gears through ignition timing to full engine management, from cartridge forks to semi-active suspension, and from vicious highsides and locked brakes to traction control slides and cornering ABS. So let’s get this right: bikes are faster than ever, as fuel efficient (given their performance, at least), no less exciting than they ever were, and there are fewer bike accidents now, with fewer casualties.

Compare that to the previous 15 years, 1985 to 2000; a period everyone nostalgically remembers as being a golden age of bike development: around a 17% peak power increase (Kawasaki GPZ900R to Yamaha R1), carbs to, er, carbs, twin disc brakes to twin disc brakes, monoshock suspension to er... you get the idea. Of course things got better – but in a mechanical, materials way; aluminium instead of steel, refining weight, steering geometry, radial tyre technology, braking and suspension performance... it was an age of refining broad principles, not today’s fine-tuning.

So, in that light, it’s easy to moan about Euro 4 and interference by Brussels, and who knows what we’d be riding if none of the regulations existed. But we are where we are, and modern motorcycling is not a bad place to be. Euro 5 in 2020? We should embrace it. Can’t wait.