HAS EURO5 RUINED OUR ENGINES?
Under the latest EU emissions laws, some bikes make less power, use more fuel and produce more C02. So, are the latest rules set to ruin our bikes?
EVERY FEW YEARS, bike firms have to hit ever-tougher emissions regulations. Devised by the European Union, these regs, which govern what comes out of a motorcycle’s exhaust and what noise it produces, have got progressively harder for manufacturers to hit. The result is that some models make less power that previous-generation ones, though not all are affected.
Compared to Euro4, Euro5 requires a 12% drop in carbon-monoxide emissions, 40% fewer hydrocarbons and 33% fewer nitrogen oxides in the exhaust gas — alongside other checks.
The regulations don’t care how new engines conform, as long as they do. A new bike failing to meet Euro5 cannot be sold in Europe, including the UK.
How do manufacturers meet Euro5?
Emissions regs aren’t a surprise; manufacturers know they’re coming and employ strategies to meet them. Broadly, two things matter — creating fewer toxins and better dealing with what you do create.
The first is about efficient combustion — burning fuel more evenly and completely. Engineering strategies such as reducing valve overlap (when valves are open at the same time), introducing variable valve timing, optimising ignition timing, improving gas-flow characteristics (swirl and tumble), precise metering of fuelling — among many others — all improve combustion.
But, secondly, Euro5 requires more effective catalysts in the exhaust. A cat ‘scrubs’ specified toxins from the exhaust gas, using chemical reactions to convert them to less-harmful compounds. For Euro5 cats ideally need to be longer, wider and closer to the combustion chamber than with Euro4. Longer because the more time passing gas ‘dwells’ in a cat, the more complete the reaction; wider because more surface area creates back pressure to help complete combustion; and closer because cats need to heat-up rapidly from cold to work effectively.
To do all that, three smaller cats in different parts of the exhaust doing slightly different jobs are better than one big one. But either way, Euro5 cats are heavier, more restrictive, require more monitoring and sensors, and are dearer than Euro4.
‘CO2 isn’t limited; burn more fuel, get more CO2’ JAMIE TURNER, PROFESSOR OF ENGINEERING
So is my Euro5 engine better or worse than a Euro4 engine?
If your engine — basically a pump — has a bigger restriction in its exhaust, it will be less efficient and have
to work harder to overcome the blockage for a given performance. So to maintain performance and drivability, manufacturers have two options: increase engine capacity or re-tune (effectively, de-tune) the existing engine to match the new restriction and attempt to offset inevitable trade-offs in performance and useability by further refining engine management strategies. Or, sometimes, they use a combination of both.
So some new-bike engines are bigger: BMW’S R1250GS, Triumph’s Tiger 900,
Yamaha’s MT-09 and Honda’s Africa Twin among others. They all make roughly the same, or slightly more, power and torque than previously but still meet Euro5. So in this respect, Euro5 has actually made them more powerful, torquier and relatively cleaner (and, in some cases, more fuel efficient). So that’s a definite good thing.
Some engines, such as Suzuki’s Hayabusa and GSX-S1000, BMW’S S1000XR and R ninet series, or Yamaha’s MT-07, haven’t been enlarged and have instead been retuned. And this is where it gets complicated because whether an engine has been ‘improved’ or ‘ruined’ depends on many factors, such as how successfully the manufacturer has retuned the engine.
But for un-enlarged Euro5 engines, it seems in some cases fuel consumption gets worse and carbon-dioxide emissions — a greenhouse gas — go up. “The criteria pollutants, as they’re called — hydrocarbons, carbon monoxide and nitrogen oxide — have fixed limits,” says Jamie Turner, motorcycleexpert professor of engineering. “Carbon dioxide isn’t a criteria pollutant but is a linear function of fuel consumption — burn more fuel, get more CO2. In a cat, the atoms are rearranged from bad emissions to CO2, water and nitrogen. But the conditions inside the cat for that reaction to meet targets are very precise — ensuring those conditions are met is what lambda sensors do.”
“In order to get your engine to compliance [ie meet criteria pollutant targets] you have to manage emissions at cold start-up but get maximum heat flow down the exhaust at the same time to heat the catalyst to its light-off temperature. That means running the engine inefficiently.”
So while meeting Euro5 for carbon monoxide, hydrocarbons and nitrogen oxides, it’s producing more CO2 greenhouse gas (not in Euro5 for motorcycles) and using more fuel to do it.
Which isn’t very green.
BMW’S R ninet series falls into this category and so does Suzuki’s Hayabusa.
But some Euro5 engines claim better fuel consumption and less CO2 than their Euro4 versions — such as Yamaha’s MT-07 and BMW’S S1000XR — possibly because the particular engine’s layout and architecture was predisposed to it.
So Euro5’s just a sham, then?
It’s difficult to point to a specific Euro5 engine and say it’s significantly better or worse than its Euro4 counterpart — some are in some ways, and aren’t in others, and vice versa. It’s not even possible to say they’re all more environmentally friendly — all definitely have fewer exhaust toxins but some add more CO2 to the atmosphere than before and use more fuel. Not the EU’S finest hour…