Roadshow

How small can car engines get?

Welcome to the golden age of engine shrinkage.

The cylinder is the heart of a car's engine but its also the enemy of modern priorities: It's where fuel is consumed and emissions are created. To solve for that, carmakers have increasingly adopted engines that can shut down their cylinders in banks or sets while running. But the newest form of cylinder deactivation is called Dynamic Skip Fire, which shuts down cylinders in random sequences or sets based on esoteric calculations made up to 200 times per second. 

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Because the number and arrangement of cylinders being shut down is so malleable, fuel economy and emissions reduction are optimized while in-cabin detection of the process is basically nil. The 2019 Chevy Silverado is an early adopter of Dynamic Skip Fire, allowing its V8 engine to run on as little as a single cylinder some times. 

Cylinder deactivation isn't new, starting its current run in 1981 Cadillacs that featured an engineering disaster known as the V8-6-4 engine. It shut down banks of cylinders mechanically, a clunky process that proved deactivation shouldn't have even been contemplated until the modern era of engine electronics.

Today's elegant cylinder deactivation, like Dynamic Skip Fire, amplifies the complementary trend toward smaller engines: The inline-4 just passed the venerable 6-cylinder engine as the most popular in US new cars, according to Experian, and 3-cylinder engines are starting to take hold. 

2017 US new car engine share 
4 cylinder: 38 percent
6 cylinder: 37.4 percent 

Today's car buyers often don't know or care about their engine's cylinder count, giving smaller engines and those that deactivate some of their cylinders welcome air cover in a market that would have eschewed them as wimpy or compromised a few decades ago. Combined with automatic start-stop technology, we are finally approaching an era when car engines will almost never burn fuel unless it's doing real work.