Small Turbo Engines Could Be Replaced By Larger Units In Pursuit Of Lower Emissions Photo:

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Trevor Collett | Oct, 19 2016 | 10 Comments

Large four-cylinder engines, small V8s and turbocharged three-cylinder donks - all have been trialled over the years as carmakers seek the ultimate compromise between power and economy.

But each has proven to be just that - a compromise - as big 4s were too thirsty and small V8s didn’t produce enough power.

Turbocharging has been seen as the leveller, particularly since around 2010, with some carmakers featuring turbines attached to smaller engines in almost every model.

The move was designed to overcome ever-stricter emissions laws, particularly in Europe, with the smaller engines able to operate ‘below the radar’ in some respects to achieve the necessary numbers while their turbochargers were passive during testing.

But as the laws tighten even further following the Volkswagen emissions scandal and with the likely introduction of ‘real world’ testing in some markets, carmakers may be about to head back-to-the-future with the internal combustion engine.

A deep analysis by Reuters suggests larger engines will soon make a comeback, with General Motors, Volkswagen, Renault and others said to be looking at scrapping small engine programs - some of which have been in place for just a few years.

"The techniques we've used to reduce engine capacities will no longer allow us to meet emissions standards," Renault-Nissan Alliance powertrain boss Alain Raposo said.

"We're reaching the limits of downsizing."

The report predicts that Volkswagen’s 1.4 litre diesel and GM’s 1.2 litre diesel, along with Renault’s 1.6 litre diesel and 900cc petrol engines are all soon to be retired. Each could be replaced in next-generation developments by larger units - up to 30 percent bigger in the case of GM.

But not all carmakers have been embracing the tiny turbo era.

Mercedes-Benz BlueTec
Mercedes-Benz BlueTec

Toyota and Mazda are two examples, with each stubbornly sticking with relatively large four-cylinder petrol engines in several mainstream models. Another is Mercedes-Benz.

"It becomes apparent that a small engine is not an advantage," Mercedes’ Thomas Weber said. "That's why we didn't jump on the three-cylinder engine trend."

For those companies that have travelled the tiny turbo route, upsizing is certainly an option, which could also be viewed as a return to normality (or the past) for some. But the solution may not be as simple as it sounds.

For starters, customers are unlikely to embrace economical three-cylinder engines without turbochargers, so simply unbolting the ‘hair dryer’ probably isn’t an option. Further, the added strain placed on the engine by drivers operating them at full-throttle for much of time, given the sudden drop in horsepower, is also likely to see fuel usage and emissions soar.

But equally challenging is the task of squeezing more efficiency from larger engines, and there’s a very real chance that some will not make the cut as emissions laws tighten.

Weight-shedding is always an option, but the costs of some lightweight materials make them prohibitive for budget-priced models.

Hybrid technology for both petrol and diesel engines has brought proven results in power and economy. But even as Toyota thrust the trend into the mainstream with its first-ever Prius, there were several carmakers who viewed the technology as a stop-gap and have more-or-less refused to embrace it, even to this day.

The recent Paris Motor Show revealed to the world that the age of electric motoring is rapidly approaching - if you argue that it hasn’t already arrived.

Mercedes-Benz, Volkswagen, Renault, Porsche, Mitsubishi and others all arrived in Paris with EV, hybrid or plug-in hybrid models.

And should the further advancement of the internal combustion engine prove too difficult or too costly, customers can expect to see EV development ramped-up even further. Watch this space.

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