On the opening day of the 2013 North American International Auto Show in Detroit, Infiniti introduced the successor to the G37—the 2014 Q50. The sport sedan is being offered with a choice of a 328-hp (245-kW) 3.7-L V6 or new Q50 Hybrid featuring Infiniti's Direct Response Hybrid System with Intelligent Dual Clutch Control. Both powertrains will be offered with rear-wheel drive or Intelligent All-Wheel Drive, and both are matched with a seven-speed electronically controlled automatic transmission.
“From early on, we had the goal of having more than just a single powertrain lineup for the vehicle,” said Bert Brooks, Regional Product Manager for the Q50. “The 3.7-L V6 engine is an engine we have used at Infiniti in the past and it’s been a very successful volume-selling powertrain for us. Using that engine as the starting point made sense, but we wanted to significantly improve its refinement, its quietness, and its fuel economy—but, of course, not sacrifice the performance. A lot has gone into it in terms of looking at the air intake on the engine, the exhaust, spending a lot of time on the transmission as well to make sure the engine is at the right point in the rpm range to deliver adequate power without making inappropriate noise.”
The hybrid powertrain combines a 3.5-L 24-valve DOHC aluminum-alloy V6 and a lithium-ion battery system with one-motor/two-clutch motor control. The hybrid system's V6 is estimated at 296 hp (221 kW) and 255 lb·ft (346 N·m), with the addition of a 50-kW electric motor net power is estimated at 354 hp (264 kW).
“The idea was to provide a powertrain that was the absolute pinnacle of both fuel economy and performance without tradeoffs,” Brooks said. “They’re still tentative figures, but we’re targeting to get up in the 355-360 range for [net] horsepower, and for fuel economy we want to get up to something around 34 highway. That kind of number with that kind of power is nowhere else in the market.”
The battery and hardware for the Q50 Hybrid are packaged behind the rear seat and in the trunk floor. Run-flat tires are fitted as standard, eliminating the need for a spare tire, and that space has been repurposed for the hybrid componentry. The split-folding rear seat was also sacrificed in the hybrid application. Despite the changes, the Q50 Hybrid “should still be in a very strong position for trunk space among HEVs,” said Brooks.
Also making its debut in the vehicle is the Infiniti Direct Adaptive Steering system, which allows advanced control of the Q50's tire angle and steering inputs, transmitting the driver's intentions to the wheels faster than a mechanical system can. Four different steering settings are offered, allowing customization by driver preference or road conditions.
“Because the system does use a completely electronic feedback loop, essentially what happens is the power steering rack has two electric actuators on it, and as those actuators move the wheels it measures how much force is required to move the tire against the road. And that changes depending on the road surface condition, how much lateral force is on the car, and so on. That information is fed to the ECU for the steering system, which is then fed back to the driver as a torque or effort he feels in the steering wheel. It’s a completely closed-loop feedback system,” Brooks said.
“The driver is completely connected at all times from the steering wheel to the tires, but it’s done electronically, not mechanically," Brooks continued. "The magic of that is because now it’s an electric signal not a mechanical one. We can filter it, tune it, adjust it in a much more easy way just with software.”
The Q50’s body design offers enhanced airflow over both the upper and lower body portions, resulting in a coefficient of drag of just 0.26. Stiffness was also a target for engineers, with an improvement in front body stiffness vs. the previous generation.
“In spite of all the improvements that we made for stiffness, we haven’t increased weight at all,” Brooks said. “The final figure I think will show a slight weight reduction from the outgoing G37, but the body stiffness is significantly improved. We use a type of high-tensile steel in various parts of the vehicle that in the past no one has used before because of a difficulty in stamping. It’s a 1.5-GPa steel. That, of course, allows us to have a stronger component but use less of it.”
The Q50 will be available in summer 2013, with additional powertrain offerings to come based on specific market needs.
“For other markets there will be other powertrains available—a four-cylinder diesel and four-cylinder gasoline engine,” Brooks said. “For the U.S., we continue to look at other powertrains as well, but don’t have an announcement today about any future powertrains.”