General Motors is about to commit to engine start-stop systems in a big way.

Start-stop systems—which shut off the engine while a car is stationary to save fuel—are already available on numerous models from multiple manufacturers.

But GM reportedly plans to offer start-stop on at least one powertrain in every model it makes by 2020.

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The decision to add start-stop fleetwide came about because of both regulatory changes and advances in hardware, according to an Automotive News (subscription required) report.

While they do improve fuel economy in real-world driving, start-stop systems are typically deactivated for EPA testing, so they don't impact ratings.

However, starting with the 2017 model year, the EPA will award credits toward compliance with Corporate Average Fuel Economy (CAFE) standards to carmakers who equip vehicles with start-stop systems.

2016 GMC Canyon

2016 GMC Canyon

CAFE requires carmakers to achieve a fleet average of 54.5 mpg by 2025, equivalent to about 40 mpg on the window sticker.

Actual fuel-economy gains can be augmented with credits for the implementation of efficiency-related technologies or features.

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Other features eligible for credits include more-efficient glass and active aerodynamics. In 2014, GM received a credit for vehicles equipped with a more-efficient air-conditioning system.

GM also plans to add new hardware designed with start-stop systems in mind.

Vehicles equipped with start-stop systems will get absorbent glass mat (AGM) batteries and tandem-solenoid starters, GM spokesperson Tom Read told Automotive News.

2017 Chevrolet Camaro ZL1

2017 Chevrolet Camaro ZL1

AGM batteries are more efficient than traditional lead-acid batteries, while tandem-solenoid starters should make starts quicker and smoother.

GM's new nine- and 10-speed automatic transmissions were also designed from the beginning to incorporate start-stop, AutoPacific analyst Dave Sullivan said.

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The transmissions—developed jointly with Ford—have accumulators that keep them pressurized when the engine is off, allowing the vehicle to move away more quickly when the engine restarts.

The 10-speed automatic will debut later this year in two performance models—the 2017 Ford F-150 Raptor pickup truck, and 2017 Chevrolet Camaro ZL1 muscle car.


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