Prior to the Tokyo auto show, Honda showed us a number of its upcoming technologies (including its new direct-injection engines), and one of the most promising is Electric SH-AWD. To review, SH-AWD stands for Super Handling All-Wheel Drive and, on current Acura products that bear the label, it signifies a four-wheel-drive powertrain that can route engine torque to either of the rear wheels to improve cornering.
Electric SH-AWD operates on a similar principle, and will be found on at least one upcoming Acura in the near future (pay no mind to the fact that the demonstration vehicle pictured here is an Accord). Instead of sending a driveshaft to the rear wheels and proportioning the power via clutches in a differential, the rear wheels simply use two electric motors. It’s a deceptively simple idea, and one that’s popped up in one form or another from various automakers (the Porsche 918 Spyder and RSR concepts feature something similar, for example). We’d have thought of it ourselves but were too busy looking for Asimo, Honda’s walking robot. He never showed.
The rear electric motors are only part of an overall hybrid powertrain concept. Up front is the latest development of Honda’s 3.5-liter V-6, now with direct injection and an output of at least 308 hp and 266 lb-ft of torque. The engine is mated to a Honda-built seven-speed dual-clutch transmission with a 40-hp DC electric motor integrated into the housing. Unlike Honda’s current IMA hybrid system, this new setup allows the engine to decouple from the electric motor. The benefit is that, during electric regeneration, all of the energy can flow through the motor (acting as a generator) into the batteries; no energy is used to spin the gasoline engine. Similarly, no battery power is wasted spinning the engine during EV-mode stints, which currently is the case with Honda’s hybrids. Interestingly, EV mode actually uses the rear motors to propel the car, which brings us back to SH-AWD.
Connected to each rear wheel is a 27-hp DC motor, either of which can deliver torque to its respective wheel or create drag through electric regeneration. The system works just like a mechanical torque-vectoring system but with much less hardware and, incidentally, less weight. When the car enters a corner, the system will send power to the outside rear wheel and drag on the inside rear wheel. In this scenario, the dragging motor can send electricity directly to the assisting motor in real time. As the car progresses through the corner, the inside rear motor will switch to electric assist to provide optimum traction. And if the lithium-ion batteries are depleted, the electric motor in the front of the car can act as a generator to make sure the SH-AWD system still operates.
With this system, Honda claims V-8 levels of acceleration and four-cylinder levels of fuel economy, without providing any specific numbers. Before you go adding up all the horsepower figures, remember that electric motors make most of their power at low speed, so the total system output is somewhere above the gasoline motor’s 308 horsepower, but we’re not sure how much higher. Both the power and economy claims might be a little ambitious. Still, we’re glad to see Honda taking a new approach to hybrids, especially one focused on performance as much as efficiency.
