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How RAM eTorque Works

by Bill SiuruJune 28, 2019
Mild hybrid engines have been tried in various models over the past decade, without really gaining traction. Now they’re making a resurgence as fuel economy becomes a more pressing need for automakers. RAM aims to make it a success story.

The all-new 2019 RAM 1500 debuted with eTorque mild hybrid technology, an efficiency-enhancing system that’s exclusive to the segment. This new feature, while potentially important to buyers seeking a fuel economy bump in the increasingly-crowded and always competitive light pickup field, is not readily understood by all. So here’s an overview on how RAM’s eTorque mild hybrid works.

Functionally, eTorque works by replacing the RAM’s conventional alternator with a more robust motor/generator in 3.6-liter V-6 and 5.7-liter V-8 HEMI engines. The eTorque-equipped V-6 mounts its Continental motor-generator in front of the engine with the pulley pointing aft. A dedicated, water cooled coolant circuit is used since the internal cooling fans in a typical alternator would not work in this configuration. In the HEMI V-8, a Magneti Marelli motor-generator mounts conventionally near the top of the engine where air cooling works fine. The 48-volt eTorque system adds 90 pounds to a the HEMI V-8 and 120 pounds to the V-6, with the water-cooling circuit accounting for the difference.

When lifting off the throttle at speed, eTorque’s motor/generator begins to generate electrical energy that feeds back to its battery pack while also smoothing transmission downshifts. It provides a brief torque boost of 90 lb-ft in V-6 RAMs and 130 lb-ft in V-8 models. Along with adding torque during shifts, it contributes torque while transitioning in and out of four-cylinder mode during V-8 cylinder deactivation. The eTorque system restarts the engine and resumes forward motion within 70 milliseconds after an auto-stop. An interactive deceleration fuel shut-off system also saves fuel.

Electrical energy in the eTorque system is stored in a 30 pound, 430 watt-hour LG Chem battery pack mounted at the rear wall of the pickup cab. The system includes a DC-to-DC converter to supply the vehicle’s regular electrical loads and charge its 12-volt starter battery.

Alternators only draw modest power from an engine’s accessory drive. However, eTorque’s motor-generators use their accessory drive belt to slow and accelerate these trucks, so the belt must be larger and stronger, and also must wrap farther around the pulley. It also requires a tensioner on both sides to keep belts tight as the motor/generator transitions from generating to motoring. The eTorque Hemi gets a larger crankshaft pully as well that improves the motor/generator’s leverage.

While Audi and Mercedes-Benz are selling similar systems in Europe, FCA (Fiat Chrysler Automobiles) is the first to market vehicles using the technology in large numbers in the U.S. With an estimated 2 to 3 mpg savings in city/combined fuel economy, eTorque delivers improved environmental performance and has the potential to have a measurable effect on FCA’s corporate average fuel economy as well.