QOTD: Variable Displacement - New Hotness or Inevitable Blowout?

qotd variable displacement new hotness or inevitable blowout

At this week’s L.A. Auto Show and Traffic Negotiation Event, Infiniti will reveal the next generation QX50 — an overdue replacement for the aged model formerly known as the EX35. While the introduction of a crossover that’s losing its V6 and rear-wheel-drive platform wouldn’t normally interest me, the model’s new engine does.

Today we’re going to discuss variable displacement and the future of internal combustion engines. Fly or flop, what say you?

A little background is necessary, in case not all of you are avid readers of TTAC (like you should be). The upcoming QX50, set to appear in showrooms next summer, will come equipped with the first-ever variable displacement engine. Earlier in November, Matthew Guy did a nice job summarizing how the engine works.

Basically, the engine is able to alter the reach of the pistons, adjusting the compression ratio between 8:1 (for power) and 14:1 (for efficiency). This effectively alters the displacement of the engine on the fly. It’s never been done before. This leads me to today’s inquiry, and a few of the things I’ve been considering recently:

  • This is a major change for internal combustion engines, and the largest shift in piston engine function in the past hundred years. Will other manufacturers quickly follow Nissan’s lead, or shy away from this sort of bold engineering move?
  • Generally speaking, major tech advances in engine technology have often been accompanied by spotty reliability for a period of time after introduction. Eventually, the wrinkles are ironed out by the manufacturer, but by that time the majority of the public has rejected the technology. Does reliability in such a complex engine concern you? Or is Nissan, builder of VQ V6 engines, competent enough in that area to assuage your fears?
  • There’s always a risk that the market will not accept a “new way” of propelling a car. But perhaps the fuel economy promised by the technology will override any other concerns. Do you think this is the sort of engine the public is brave enough to purchase, assuming the idea of variable compression is something they can comprehend?

One more thing. Infiniti and Nissan are betting big on this technology’s success to ensure a return on their investment. After a development timeline of over 20 years, the company has decided against employing the engine on some high-end, limited-production halo car, installing it instead in a mid-market crossover which will theoretically sell many thousands of units. If it fails, it’s going to fail spectacularly and publicly. If it succeeds, it’s going to change the future of the Infiniti lineup at the very least, and perhaps passenger cars as a whole.

Use your crystal ball, B&B. What do you see in the future of the variable displacement engine?

[Image: Infiniti]

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  • Newenthusiast Newenthusiast on Nov 29, 2017

    There's a lot of engineering talk here that I don't understand. I'd probably have to see ho it worked vs a traditional engine design to get it. That being said, I'm interested enough in what it promises to keep an eye on the reliability numbers on models with this engine going forward. Much like Mazda's SkyActiv - X, if it gives the models its used in a noticeable difference in fuel consumption, and it turns out to be otherwise an engine with no extreme reliability issues (no one is expecting perfection), then it's going to be a plus for shoppers who look at fuel efficiency and a non-issue for almost anyone else. If it works as they say it will, the question becomes will other automakers try to develop similar technology?

  • Rpn453 Rpn453 on Nov 30, 2017

    Good discussion here. It's not a vehicle that interests me (I doubt that Infiniti ever will sell another vehicle that interests me) but if I were asked for my opinion I'd simply recommend giving the technology some time to prove itself.

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