As truck engine displacements shrink, power and fuel efficiency grow

“The industry stuck with 15-liter engines because of some perceived durability,” Roeth said. “I think we’re seeing that it was mostly a perception. We don’t need the (higher) horsepower for most freight movement.”

Engines with greater than 14-liter capacity captured 49% of the over 10-liter market in 2019, said Tom Rhein, president of the powertrain information supplier. 

“Today’s smaller engines deliver more horsepower and torque than the smaller engines of the past,” said Kenny Vieth, ACT Research president. 

For example, the Cummins (NYSE: CMI) X12 inline six-cylinder engine puts out 455 horsepower with 1,700 pound-feet of peak torque between 1,400 and 1,900 rpm, comparable ratings to some larger displacement 13- and 15-liter engines. It weighs just 2,050 pounds compared with Cummins’ X15 Efficiency Series engine at 2,961 pounds.

Avoiding engine weight can translate to extra available weight for freight.

“This is probably the best engine in terms of weight-to-power ratio that we have, which works really well, particularly in vocational applications,” Srikanth Padmanabhan, president of Cummins engine business, told analysts at Cummins Investor Day on Nov. 25.

Originally developed for the Chinese market, the re-engineered 11.8-liter X12 is becoming a go-to alternative for many North American manufacturers.  

The 12.4-liter International A26 from Navistar (NYSE: NAV) and the 12.9-liter MX-13 engine from Paccar Inc. (NASDAQ: PCAR) are also in this size class. 

“All the new engines that have come in recently are in the 12-to13-liter range,” Roeth said. “That says the industry saw all this coming. Weight and cost and fuel efficiency are reasons to go smaller. Passenger cars have been doing this for years.”

More medium-duty Class 5-7 trucks offer gasoline options in place of diesel, Rhein said.

Under attack

While the diesel-powered engines are getting smaller and emitting less pollution, they are still a target of zero-emissions proponents, especially in California. Cylinder counts and engine displacement are irrelevant in electric trucks where battery-powered electric systems replace engines.

“Diesel power is under attack long-term for use in on-highway commercial vehicles,” Vieth said. “Alternative power is being developed, tested, and refined, even as diesel engines are transitioning to become more fuel efficient and clean.”

California uses generous incentives to push electric vehicles. A demonstration fleet of electrified Class 8 heavy-duty and Class 6 medium-duty Freightliner models is beginning to rack up significant miles in both fixed-route deliveries and drayage from the ports of Los Angeles and Long Beach to the Inland Empire.

More electric truck test fleets are coming. Anheuser-Busch, for example, plans to begin delivering beer in Southern California in a fleet of electric trucks in 2020. 

As batteries become more energy dense, the range between rechargings will grow and cost differences with diesel engines will shrink. Nikola Motor, which is mainly pursuing hydrogen-powered fuel cell technologies said recently it will reveal a battery technology next fall that could be the long-sought breakthrough.