How the Internal Combustion Engine Is Keeping Pace

Competition with EVs is helping improve the efficiency of the conventional automotive engine
Photograph: Shutterstock

CHICAGO —Norway, India, France, Ireland and the United Kingdom: Judging by the range of countries that have pledged a future ban on the sale of new gasoline- and diesel-powered vehicles, the internal combustion engine (ICE) seems to have an expiration date, ranging anywhere from 2025 to 2040. Some major automakers have also pledged to shrug off the ICE: Volkswagen has targeted 2026 as its last model year for gasoline- and diesel-powered vehicles as it puts its full weight behind electrification.

Despite the pending bans, fuel-economy requirements and the dawn of electric vehicles (EVs), don’t count out the ICE just yet. Regulatory and competitive pressures are squeezing more miles—and years—out of the 143-year-old technology.

“My grandchildren will be retired before the ICE goes away; I’m not sure it ever will go away,” said James Martin, senior research analyst of North American powertrain and compliance forecasting for London-based IHS Markit.

Promising Technologies

“Competition from electric vehicles is making companies that specialize in and rely on the ICE to get better at it, and better at making it efficient,” Martin said, pointing out how automakers such as Toyota and Mazda are producing engines with thermal efficiencies—a measure of the percentage of burned fuel an engine can convert to propulsion—in the 41% to 42% range. This compares to a more typical high 20% to low 30% range.

Meanwhile, as automakers react to regulatory pressures, including tougher fuel economy standards, the amount of money per mile per gallon improvement they are willing to spend to get a technology to market is increasing, he said. “Where before you wouldn’t put a technology on it if it cost more than $10 per mile per gallon of improvement, now companies are looking at technologies that are costing $25, $30 per mile per gallon improvement to meet regulations because the cost of electrification is so much higher,” he said.

What are automakers spending their research and development money on? Martin points to some of the most promising approaches.

Turbocharging. One technology makes small engines seem bigger: downsizing the engine but maintaining its power by adding turbochargers. These smaller, lighter engines use less fuel because they run at higher cylinder pressures. Turbocharging and downsizing combined offer fuel economy improvements of 5% to 7%.

Electrification will make these engines even more fuel-efficient. “In some cases, they’ll be able to start providing boosts to the engine before the vehicle even starts moving,” Martin said. “It eliminates what is called ‘turbo lag’—where you hit the gas pedal, the engine starts to go and then the turbo comes in and gives you a really big push. With electric turbochargers, you’ll get that boost early on so you don’t get that hesitation followed by a big push. You just get a gradual acceleration.”

Cylinder deactivation. Another promising technology—cylinder deactivation—makes a large engine in a vehicle such as a pickup or SUV seem smaller in terms of its fuel consumption. With this technology, the engine shuts off fuel to a portion of its cylinders when they are not needed—for example, a pickup cruising on a highway vs. hauling a heavy load in the mountains. A newer form of this technology, Dynamic Skip Fire from Delphi Technologies, can dramatically cut down on the number of cylinders in use, allowing a Chevrolet Silverado pickup, for example, to run on as few as one cylinder or as many as all eight cylinders.

Fuel-economy improvements can range from 4% to 5% for older forms of cylinder deactivation, and up to 10% to 12% for dynamic forms where each cylinder independently turns on and off during each cycle as needed.

 HCCI. In 2018, Mazda Motor Corp. introduced the Skyactiv-X engine, which the Japanese automaker described as a “next generation” ICE.

“The technology they’re using is called homogeneous charge compression ignition (HCCI). It basically allows a gasoline engine to run on a very diesel-like cycle for extended periods of time,” said Martin. Instead of firing a spark plug to ignite the mixture of gas vapor as in a gasoline engine, the Skyactiv-X compresses the fuel mixture so tightly that it ignites—just as in a diesel engine. The result is 15% greater fuel efficiency and torque than in a conventional engine, according to Mazda.

Five years ago, Martin would have described HCCI technology as interesting in theory but never production-ready. It builds on other technologies and capabilities that were not cost-effective for most automakers to implement together. “Mazda has apparently found a way to make it work,” he said.

Variable-compression turbo. Another technology that Martin would have described as great in theory but never production-ready is Nissan Motor Co. Ltd.’s variable-compression turbo (VC-Turbo) engine, also introduced in 2018. The 2-liter turbo engine can shift its compression ratio on the fly from a fuel-efficient 14 to 1 to a more powerful 8 to 1. Again, Martin considered the technology too complex: It introduced a new set of moving parts and requires a control system to time the movements. But Japan-based Nissan figured it out and is adding the VC-Turbo to its Infiniti QX50 and the 2019 Nissan Ultima. The new engine offers a 15% improvement in the combined fuel economy of the Ultima’s earlier 3.5-liter V6 engine.

Finding a Sweet Spot

Improving transmission technology can also go a long way in boosting the fuel economy of the ICE, allowing the engine to operate longer in a “sweet spot” of its ideal conditions, Martin said. And even greater improvements to the fuel economy of the ICE are capable with electrification.

“People are starting to see synergies between different forms of electrification enhancing the ICE instead of just competing with it,” he said, pointing to the proliferation of mild and full hybrid engines being introduced by automakers who are seeking to meet toughening fuel economy targets in the United States and around the globe.

“To the extent that electrification of the vehicle takes some of the burden off the ICE, it allows ICE developers to design that engine to work within the most efficient bandwidth for that engine, so they can improve fuel economy that way,” he said. Mild hybridization can offer a 5% to 15% improvement in ICE fuel economy, while full hybridization pushes this range to 15% to 20%, and plug-in hybrids can see a 25% or greater savings.

Keeping the ICE alive also has a human element. Not every consumer will be able to drive today’s EV, which can take up to 30 minutes to charge at 80% battery capacity. “For some people, an electric car will be ideal; for some, a nightmare,” Martin said. “They need something where they can replenish the energy source in minutes, not hours. If they have a vehicle with an ICE but some enhancements through electrification, they can still achieve both ends.”

Meanwhile, not every country can assume a fully electric transportation infrastructure in the immediate future. Martin expects those that have announced gasoline- and diesel-vehicle bans to come around to a happy technological medium between ICE engines and electric motors.

He cites the softening of California’s original zero-emission vehicle (ZEV) program. The mandate, adopted in 1990, had originally required that major automakers make 10% of their new vehicles ZEVs by 2003 if they wanted to continue to sell in the state. In response to marketplace realities and lagging consumer demand for EVs, California gradually adjusted the mandate to allow different degrees of ZEVs.

“It’s easier to set a policy and back away from it to what makes sense than to allow the industry to organically get to the right position,” Martin said. He expects a similar shift in countries that have set ICE bans.

“Over time, they go back to what’s possible and what makes the most sense economically for automakers and the regions,” he said.


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