2019 Infiniti QX50 crossover to debut variable-compression engine


Infiniti QX50 concept, 2017 Detroit auto show

Infiniti QX50 concept, 2017 Detroit auto show

Enlarge Photo

Efforts by automakers to increase fuel efficiency and reduce carbon emissions have intensified in recent years as emission rules have tightened and the effects of climate change are better analyzed.

While electric cars and hybrids will grow in popularity, the internal-combustion engine remains the default way of power—and likely will for years to come.

The latest effort to make engines more fuel-efficient will come from Nissan's premium brand, Infiniti, in the form of itsnew  variable-compression turbocharged (VC-T)  inline-4 engine.

DON'T MISS: Infiniti variable-compression engine: more complexity, incremental gains

The luxury make plans to launch the new powertrain in the 2019 Infiniti QX50 crossover when the vehicle debuts next year.

VC-T will produce a 27-percent increase in combined fuel economy over the current QX50, according to an Automotive News report (subscription required) published on Thursday.

But, the engine won't sacrifice performance, with 268 horsepower and 288 pound-feet of torque. Infiniti said the QX50 will sprint from 0 to 60 mph one second faster than its direct luxury crossover rivals.

Infiniti QX50 concept, 2017 Detroit auto show

Infiniti QX50 concept, 2017 Detroit auto show

Enlarge Photo

The VC-T engine boosts fuel efficiency by varying its compression ratio via a device Infiniti calls the Harmonic Drive.

The device uses an electric motor and mechanical linkages to adjust the connecting rod between each piston and the crankshaft, thereby varying the maximum height a piston can reach within the engine's cylinder.

The less space remaining in the combustion chamber above the piston, the higher the compression ratio and the greater the engine output.

READ THIS: Infiniti plans VC-T engine with variable compression ratio

Infiniti said its technology is seamless and requires no additional effort by the driver. Engine-control software changes the compression ratio with driving conditions to prioritize either fuel economy or added power when needed.

Traditional internal-combustion engines with conventional connecting rods feature a fixed compression ratio, which makes Infiniti's technology novel.

However, Mazda will achieve the same effect as the VC-T engine with its Skyactiv-X engine, which takes a very different approach to varying compression ratio.

Infiniti VC-Turbo engine

Infiniti VC-Turbo engine

Enlarge Photo

Mazda has incorporated aspects of homogenous charge-compression ignition, or HCCI, into the latest variant of its SkyActiv engine and powertrain series.

While a traditional HCCI engine has no spark plug to ignite the fuel-air mixture and cause combustion, Mazda's Skyactiv-X engine uses a spark plug to ignite a very small amount of rich air-fuel mixture.

That spreads a pressure wave inside the combustion chamber that further compresses the lean air-fuel mixture—which then ignites on its own without a spark.

CHECK OUT: Mazda's SkyActiv-X: diesel fuel economy from gasoline engine

The Mazda system relies on extremely fast calculations of the conditions inside each cylinder and the car's power demands in the fractions of a second leading up to each combustion event, along with precise high-pressure injectors and a strengthened engine block.

These increasingly complex methods likely represent the internal-combustion engine's next and perhaps even its final frontier.

2019 Infiniti QX50 spy shots - Image via Collin Brown

2019 Infiniti QX50 spy shots - Image via Collin Brown

Enlarge Photo
2019 Infiniti QX50 spy shots - Image via Collin Brown

2019 Infiniti QX50 spy shots - Image via Collin Brown

Enlarge Photo
2019 Infiniti QX50 spy shots - Image via Collin Brown

2019 Infiniti QX50 spy shots - Image via Collin Brown

Enlarge Photo
2019 Infiniti QX50 spy shots - Image via Collin Brown

2019 Infiniti QX50 spy shots - Image via Collin Brown

Enlarge Photo

Twenty years from now, it's possible that we'll look back at these techniques as increasingly complex and expensive engineering to keep an aging technology afloat.

For that to be the case, however, the cost of battery-electric cars must continue to fall to the point that they're competitive in sticker price with their gasoline counterparts.

Until that point, such complex technologies will continue to appear in an effort to boost the efficiency of a device—the combustion engine—that wastes more than half its fuel energy in heat and noise.

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