WHAT DOES EURO 4 MEAN FOR EXHAUSTS?

We all talk blithely about Euro emissions regs – but what actually are they? Well, Euro emissions rules on exhaust pollutants started with Euro 1 on bikes back in 1999, and this placed limits on the amount of CO (carbon monoxide; a poison), HC (unburnt hydrocarbons; soot and oily fumes) and NOx (Nitrogen oxides; lung-irritating gasses) a bike can produce per kilometre. Euro 1 wasn’t too strict, and most bikes easily complied. Euro 2 appeared in 2003, and was a bit stricter, so we started to see catalysts appearing in some bikes (though the spread of fuel injection did much of the cleaning up job).

In 2006, Euro 3 rules appeared which essentially halved the amounts of pollution permitted. And the latest Euro 4 rules broadly halved the amounts allowed again. Next up is Euro 5, in 2020 – and it looks like a doozy, with more massive cuts in the pollutants allowed. Expect even more power-sapping exhaust tech then…