Infiniti to launch first variable compression ratio engine at Paris show

Published: 15 August 2016

► Infiniti launches variable compression
► New engines bow in at Paris show
► Claim ‘significant’ CO2, consumption cuts

Infiniti will showcase its new variable compression ratio engines - the world’s first in series production, it claims - at the 2016 Paris motor show.

Badged VC-T (Variable Compression-Turbocharged), the new technology will be applied to Infiniti’s four-cylinder petrol turbo engines from 2018, and will be rolled out across the road car range in due course.

We're expecting to see the 2.0-litre turbo feature in a refreshed QX Sport concept car at the French car show.

How variable compression ratios work

Infiniti is holding some of the technical detail back for its Parisian debut, but essentially the new petrol engines have a mechanism that lets the pistons reach a different height depending on the driving mode - thereby adjusting the compression ratio seamlessly.

Conventional internal combustion engines have a fixed compression ratio; the ratio by which the piston compresses the fuel/air mixture from the bottom of its stroke to the top. So if a combustion chamber has a volume of 1000cc with the piston at the bottom, and 100cc when the piston is at the top of its stroke, that's described as a 10:1 radio.

Infiniti has worked out how to vary the rate from 8:1 for sporty response to 14:1 for maximum efficiency.

How new Infiniti variable-compression ratio engine works

It sounds like a clever set-up which could disrupt historical engineering logic, letting the engine be set up for power or cleaner emissions.

The benefits

As well as letting the engineers tune the engine to provide more power or economy depending on the drivers’ needs, variable compression ratios are also said to provide ‘significantly reduced fuel consumption and emissions, plus greatly reduced noise and vibration levels.’

It’s also said to be lighter and more compact than comparable conventional engines, as no counter-balances are required on the crankshaft. Parent company Nissan has been developing the technology for more than 20 years, it said.

Roland Krueger, president of Infiniti, added: ‘VC-T technology is a step change for Infiniti. It is a revolutionary next-step in optimising the efficiency of the internal combustion engine. 

‘This technological breakthrough delivers the power of a high-performance 2.0-litre turbo gasoline engine with a high level of efficiency at the same time.’

By Tim Pollard

Editorial director of CAR's digital publishing arm. Motoring news magnet

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