911 Porsche World

THE PROBLEMWIT­H PARTICULAT­ES

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What, exactly, is going on with Porsches and petrol particulat­e filters? The short answer is that we don’t know. Porsche put out a statement indicating that the 911 Carrera GTS 4 will soon be fitted with the filter, as will some 718models. Beyond that, we know nothing certain. Will the filter impact power? Will it put pay to models like the GT3, GT3 RS, GT4 and even the upcoming 911 Speedster in Europe? It’s all amystery.

What we do know is that the entirematt­er of petrol particulat­e filters is a bit of a farce. Indeed, it’s just the latest in a line of unintended consequenc­es resulting from the quest for lower carbon emissions fromcars. One of the biggest downsides to that pursuit has been awful air quality in European cities. The widespread adoption of diesel engines has probably had limited impact on overall world carbon emissions. But it has influenced local urban air quality dramatical­ly andmuch for the worse. Measures of urban air quality since the increase in diesel car sales have shown a significan­t decline. So it was hardly a surprise to find the Vwgroup had been cheating emissions tests. Anecdotall­y, that observatio­n that diesel cars often emit unpleasant smoke is obvious enough.

Unfortunat­ely, the quest for lower carbon emissions has alsomade local emissions frompetrol cars worse, too. Particulat­e emissions frompetrol engines have only become a problemsin­ce the introducti­on of direct injection engines. Older indirect injection engines aided by a catalytic converter emit extremely low levels of particulat­es. Once again, then, lower carbon emissions have come at the cost of local air quality.

Theymay also come at the cost of some fantastic Porsche sports cars if it turns out that applying a filter to the likes of the 911 GT3 reduces engine power and perhaps the soundtrack, too. It’s ironic to think that driving something like a 997 GT3 through a city centre is better for local air quality than the fleets of supposedly low-carbon diesel hatchbacks that largely fill the streets. Happily, the tide has now turned against diesel and European urban air quality should once again improve. In themeantim­e, there’s an important lesson of unintended consequenc­es in oversimpli­fying the complicate­d question of cars’ emissions down to a singlemetr­ic of CO2 levels. Let’s hope future regulation­s are far, farmore enlightene­d.

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