It’s no secret that in some countries diesel has fallen out of favour due to emissions and other complex issues. One technical alternative that has been proposed relates to a petrol engine with Variable Compression Ratio (VCR).  VCR is becoming increasingly desirable as it offers several advantages due to its flexible nature when it comes to fuel economy, CO2 emissions and power on demand. 

Till now, we have heard about such experimental concepts and for the first time a car maker has been able to make it commercially successful. Infiniti, the luxury brand of Nissan has announced that the all-new 2019 QX50 SUV will be sold with world’s first production-ready variable-compression ratio engine.

More than 20 years in development, INFINITIís new four-cylinder turbocharged gasoline VC-Turbo engine represents a major breakthrough in internal-combustion powertrain technology. VC-Turbo technology signifies a new chapter in the story of the internal combustion engine ñ engines are no longer limited by a fixed compression ratio. The ingenuity of VC-Turbo engine technology lies in its ability to transform itself and seamlessly raise or lower the height the pistons reach. As a consequence, the displacement of the engine changes and the compression ratio can vary anywhere between 8:1 (for high performance) and 14:1 (for high efficiency). The sophisticated engine control logic automatically applies the optimum ratio, depending on what the driving situation demands.

Arguably, this development has been billed as a breakthrough in engine technology application. In the Infiniti SUV, the VC-turbo engine will displace 2.0-litre. The secret to the unit is that it is equipped with a multi-link system that continuously raises or lowers the piston’s reach to change the compression ratio on-the-go. The figure varies between 8:1 for sportier driving and to 14:1 for more efficient driving, according to the manufacturer.

The engine offers 268hp at 5,600 rpm and 280lbs-ft of torque at 4,400 rpm in its most potent configuration. The sprint from zero to 96km/h takes between 6.7 and 6.3 seconds depending on how many wheels receive power. In tests, Infiniti engineers have noted fuel economy improvements of 35 and 30 per cent, respectively, over the outgoing V6.

Other manufacturers like Mercedes-Benz have also been researching similar ideas. In 2007, an S-Class based F700 experimental concept car was fitted with Diesotto engine which was designed to offer both technologies of diesel and petrol engines in one unit. However, a decade later, it has not made it to production, perhaps due to technical issues.

Infiniti four-cylinder variable compression ratio engine

If the Infiniti VC engine is able to deliver tangible results as promised, then it could be the key for many diesel-dependent automakers who are desperately searching for alternatives.

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