Twinster-Crazy: AWD-Based Tech That Improves Driving Fun and Fuel Savings – Technologue

Opinion


Global regulations are driving the vehicle fleet toward econobox efficiency and/or increased electrification. But to succeed in a cheap-gas economy, these fuel/electron sippers will need to be as fun and comfortable to drive as our current favorite carbon spewers. GKN Driveline recently showed off several “life hack” technologies for preserving driving fun as the carbon screws tighten—including riffs on the company’s Twinster all-wheel-drive system, which gave the Ford Focus RS its drifting mojo and saves fuel by disconnecting the AWD hardware in myriad vehicles from GM, FCA, Jaguar Land Rover, and others.



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Photo courtesy of Dean Smith

Because these technologies are easiest to experience in low-traction conditions, I ventured to a frozen lake near Arjeplog, Sweden, to try them. First, a quickie refresher on Twinster: This AWD system eschews differential gears in favor of clutches on the left and right halfshafts. Engage them both fully, and you get a locked diff. Engage them variably, and they deliver torque vectoring. Release them both, and you can idle the engine and/or the driveline components to save fuel.

First up was a cost-reduced system that keeps two clutches but activates them simultaneously (Siamese-Twinster?), halving the number of valves and actuators needed. There’s no torque vectoring, but the system nevertheless made a Jeep Renegade much driftier than a similar open-diff Renegade on hand for comparison. Its locking function also delivers superior performance off-road and on surfaces with differing friction left and right. Pricing is only slightly more than an open-diff system with a single rear-axle disconnect clutch.

Next up was a mighty rear-drive BMW M3 fitted with a beefed-up Twinster axle in place of the limited-slip differential. This adds torque-vectoring capability, and I was abundantly assured that the clutches in this system can withstand repeated hard launches as easily as similar clutches in automatic transmissions. These clutches also serve as a smarter, less vulnerable “fuse” to prevent pricier driveline damage when enthusiasts go overboard boosting the engine and/or fitting ultra-grippy tires. And engineers claim that opening the clutches for engine-off “sailing” can reduce fuel consumption by 1 to 8 percent depending on the test cycle.

Other interesting innovations were presented in the hybrid and fully electric space. A new Multimode plug-in hybrid transaxle couples an electric motor to a combustion engine via a Prius-like planetary gearset—with the motor either acting as a generator to vary the output speed of the engine’s input at lower speeds or helping pull, sometimes with the engine locked to the output.



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