The industry’s target for powertrain technology is obvious: improve efficiency. It’s not only being forced by legislation but also by consumer demand and the cost of fuel.
As an OEM, if you don’t make vehicles more efficient then your market share will decrease, and no company wants that. But costs mean that there has to be a balance between how far you can push efficiency before the vehicles you sell become unaffordable.
There’s so much chatter about electrification and the revolutionary impact it could have – and no doubt in time it will change our approach to powertrain development – that quite often the improvements being made to traditional technologies are skirted over.
Everybody knows that the combustion engine has a long life left, and it is how these are tuned, adapted and updated that will have the biggest short-term impact on how efficient vehicles can become.
And the key technology is the turbocharger, which has been with us since the early 1900s. I doubt that Alfred Büchi, the inventor of the turbo, realised how important his innovation would be when he submitted his first patent in 1905, but he was fully aware of the potential benefits. He had always maintained that combustion engines just weren’t efficient enough, and eventually, after years of research, in 1925 he succeeded in mating a diesel engine to one of his turbochargers, improving the efficiency by more than 40%.
Fast forward to today and name a diesel engine in a passenger vehicle that doesn’t benefit from a turbo. And gasoline engines are fast following suit. My prediction, however obvious it may be, is that there will be very few naturally aspirated gasoline engines left in production in the next decade.
The gains that Büchi achieved may not be available, but there are still considerable improvements that can be made through increasingly controllable turbocharger systems. Mono-scroll, twinscroll, variable geometry, the technologies are there and being developed to help firms achieve their targets. And it doesn’t matter what vehicle you choose, whether it’s a city car with a three-cylinder engine or a high-performance supercar with a V12, forced induction increases efficiency.
Porsche has been well known for its naturally aspirated flat-six units for decades, but even it is shifting to charged engines as it seeks to balance the need for efficiency and performance. In the firm’s latest vehicles that use the marque’s new family of six-cylinder units, acceleration values are improved by up to 5% but at the same time the standard fuel consumption is reduced by up to 13%. That equates to fuel efficiency figures of between 8.3 and 8.7 litres/100km and carbon emissions of 169g/km and 174g/km in the Porsche 911 Carrera and Carrera S. A stage further in the 718 Boxster and Boxster S, which use charged flat-four engines, the figures are 6.9 and 7.3 litres/100km and 158g/km and 167g/km respectively.
That’s real progress. The naturally aspirated 2-litre engine in my 10-year-old D-segment Mazda6, which is much less powerful, emits more than 200g/km CO2, and I know which vehicle would be more fun to drive.
There will always be some who see what the likes of Porsche are doing and lament that we’re moving away from engines that only rely on atmospheric pressure to feed air into the engine, but you can’t stand still.
Some may argue that a naturally aspirated engine gives better response and a more involving drive, but it doesn’t mask the fact that thermal efficiency is below 40%. And that is what needs to change, otherwise CO2, NOx and particulate emissions will never come down far enough.
Mass adoption of electrified powertrains will come, and with it drastic reductions in emissions and a significant boost to overall efficiency, but it’s better-known technologies such as turbochargers that will help the industry to meet its short-term needs.