What is under the QX Concept’s hood? (Jerry Garrett Photos)
PARIS
While a new generation of electric cars, some fancy design concepts and shapely new models (cars, not booth babes) captured the spotlight at the 2016 Paris Motor Show, the technological star of the show was to be found at the Infiniti stand.
It was not the muscular-looking QX Sport Inspiration concept on display, but the production version of that vehicle coming in 2018 is likely to be first one to carry that technology. And it’s not the gleaming 2.0-liter turbocharged engine that is on the stand, next to the QX – although you’re getting warmer.
It is the technology that is inside that engine, which Infiniti calls the VC-Turbo. The VC part of its nomenclature refers to Variable Compression – and this is a technology that could revolutionize the auto industry, and make existing types of gasoline-powered engines obsolete.
2.0-liter VC-Turbo
Without getting too “Inside Baseball” on you here, all internal combustion engines have a fixed compression ratio – a value that represents the ratio of the volume of a cylinder’s combustion chamber from its largest capacity to its smallest capacity.
The most common ratios are in the range of 8:1 to 14:1, although they might go as low as 6:1 or up to 17:1 for Formula 1 cars. Generally speaking the higher the compression ratio, the faster the car it is in; lower skews toward more economical operation.
Heretofore, engine designers have had to choose what kind of performance they wanted from an engine. Then, a design was created around that ratio.
“Every production engine ever built,” Infiniti says, has been stuck with a fixed compression ratio. You pick one compression ratio and stick with it.
That’s why some cars are race cars, and others are grocery-getters.
Until now.
In the VC-Turbo technology, the engine is designed with articulating, multi-link moving parts to facilitate operation at different – variable – compression ratios, depending on throttle demand. In the instance of the Infiniti engine this is a range of 8:1 to 14:1 (and every ratio in between). So this gives the engine management system a choice of the optimal range of operation at all times.
It is sort of the best of all worlds, in terms of engine performance – power when you need it, and economy when you don’t.
This explanation is a huge over-simplification on my part, because it is all really complicated, in engineering terms. Over 300 key patents, and even more lesser ones, have granted over the two decades that it took to develop this engine; final performance and durability testing were carried out in cooperation with the Renault and Red Bull Infiniti F1 teams.
Chief engineer Shinichi Kiga wasn’t even quite sure how to define it when I asked him whether the VC Turbo is an engine, or a technology.
“Both,” he said, after some thought. “Some of both. It is the technology inside this engine.”
The technology is scalable, he added, so it could be built inside other engine architectures. The engine on display here is an inline four-cylinder design, but it could easily be expanded to an inline-six, or eight, or even larger. But then it might get to be an unwieldy size. “Probably not 16,” he added, smiling, thinking of what kind of power an engine like that could generate.
Besides the range of performance, the VC-Turbo technology fits in a smaller engine footprint – much smaller than, say, Infiniti’s venerable 3.5-liter V6, which is about as powerful. Because it is smaller, it also saves weight: The 2.0 turbo here is 25 kilos, or 55 pounds, lighter than the V6.
That’s a ton, in terms of automotive component weight – and those are the types of gains in weight-savings and efficiencies engineers dream of. Many gains are measured in mere ounces.
The little 2.0-liter turbo here produces 268 horsepower and 288 foot-pounds of torque, Mr. Kiga said. That’s power comparable to a V6, but it is “27 percent more efficient” in terms of fuel economy and operation, Mr. Kiga said.
So this is a very big deal. Imagine a gas engine with diesel fuel economy. In this instance, that’s like a 40 m.p.g. gas engine jumping up to a 62 m.p.g. capability.
I once asked Bob Lutz, former co-chairman of General Motors, why GM seemed slow to ditch old fashioned gasoline engine technology, in favor of exciting new ideas like electric motors and battery power. For one, there is a huge “installed base” of gas-engine cars; “tens of millions of them” and they aren’t going to give way to EVs or fuel cell cars overnight, he pointed out, so change will be incremental at best.
“And I’ve seen what is in the development pipeline – way down the road, five, ten, 15 years from now – in gasoline engine technology,” Mr. Lutz said. “And I believe the old internal combustion engine still has a few tricks up its sleeve. Some big improvements – big leaps forward – in efficiency could be ahead. I see a lot of potential – a lot of life left in the old gas burners.”
It would appear variable compression ratio engine technology could be one of those tricks.
Jerry Garrett
October 5, 2016
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