Cylinder deactivation can help boost the fuel economy of a car or truck by shutting down some of its engine's cylinders under light loads.
But what happens when engineers try to add that feature to an engine that doesn't have that many cylinders to start with?
The turbocharged Ford 1.0-liter EcoBoost three-cylinder is already one of the smallest-displacement engines in production; now Ford is experimenting with adding cylinder deactivation.
The carmaker is assessing whether cylinder deactivation for the three-cylinder engine would be workable, according to Green Car Congress.
Its conclusions thus far were presented by Dr. Andreas Schamel--head of research and advanced engineering for Ford Global Powertrain--at the Vienna Motor Symposium in May.
The main issue with cylinder deactivation on the 1.0-liter engine is the vibration that occurs when some of the cylinders are shut down.
Shutting off one cylinder--which effectively cuts displacement to about 666 cc--results in an uneven firing order, producing unacceptable levels of vibration.
So Ford experimented with "rolling" cylinder deactivation, varying the number and sequence of the deactivated cylinders.
Engineers tested both conventional and rolling deactivation on a Focus equipped with the 1.0-liter engine and a six-speed manual transmission on the roads around Cologne.
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Over 34 miles of city and rural roads, they found that the engine operated in cylinder-deactivation mode "a significant portion" of the time.
The test car was also equipped with a dual-mass flywheel and pendulum absorber to further reduce vibration.
Engineers found that these additions were so effective that there was essentially no difference in perceived vibration between conventional operation and the two modes of cylinder deactivation.
2015 Ford Focus
They also estimated fuel-economy improvements of 4 to 6 percent in the test car's prototype installation.
Rolling cylinder deactivation was found to be the most fuel-efficient mode of all, but also the most complex to implement.
Because it requires control equipment for all three cylinders rather than just one, the rolling system would likely be more expensive if it was put into production.
MORE: 2014 Ford Fiesta 1.0-Liter EcoBoost: Quick Drive Report (Jan 2013)
Not that Ford is planning that.
While such a system hasn't been ruled out for future production, the company says it has no plans to commercialize it right now.
We say: Wait and see.
[hat tip: Max Looker]