Cylinder deactivation has become an important tool for squeezing better fuel economy out of larger-displacement engines.
It allows engines to shut off fuel supply to some of their cylinders under light loads, effectively cutting displacement when extra power is not needed.
That's typically accomplished by deactivating no more than half of an engine's cylinders.
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But there's a new system under development that could take a more aggressive approach.
Called Dynamic Skip Fire (DSF), it enables a V-8-powered vehicle to cruise smoothly at highway speeds on just two cylinders.
It's based on an algorithm created by Silicon Valley startup Tula Technology, and is being developed in concert with General Motors and Delphi, according to Automotive News (subscription required).
2015 Chevrolet Silverado 1500 LTZ
The three companies believe DSF could improve fuel economy by up to 21 percent, and reduce emissions by nearly the same amount.
The system operates on all cylinders in an engine, and can vary which cylinders fire to maintain proper operating temperature and smoothness.
It uses software to reactivate cylinders as needed, essentially responding to how hard the driver pushes on the accelerator pedal.
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Tula notes that a V-8 SUV--like the GMC Yukon Denali it uses to demonstrate its system--only requires 30 horsepower to maintain a steady cruise at highway speeds.
In that scenario, six of the eight cylinders would be shut down.
DSF can work on all configurations of gasoline engine--including both V and inline--with four cylinders or more, according to Jeff Owens, Delphi chief technology officer.
2015 Cadillac Escalade Platinum
It also uses the cylinder-deactivation hardware already installed on some engines.
GM's stock cylinder-deactivation system uses special lifters to stop the flow of oil to valves.
A 16-valve V-8 engine has these lifters on eight valves, but adding DSF would simply require adding them to all valves, as well as some added engine-control software.
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Depending on displacement, installing DSF could cost a carmaker $300 to $600 per engine, according to estimates from Tula and Delphi.
Delphi CTO Owens believes cars equipped with DSF could be on the road by 2020.
Given GM's apparent interest in the technology, combined with the high profitability of its largest and highest-volume pickup trucks and SUVs, those may well be larger vehicles from one of its brands.