Honda engineers have given a glimpse into the technology that could underpin the next-generation NSX supercar. Two new chassis set-ups were demonstrated this weekend at Honda’s Tochigi Research and Development centre, both fitted into new-generation Accord saloons. Autocar was able to sample both prototypes on Honda’s handling circuit.
One of the Accords was fitted the prototype Super-Handling All-Wheel Drive hybrid drivetrain. The other was fitted with a new electronic rear-wheel steering system. Both are said to be designed to ‘significantly enhance handling and driver pleasure’.
Honda engineers say that the ‘Precision All Wheel Steer’ technology is the closest to realisation, with the potential for it to appear in production within two years. Work on the SH-AWD hybrid drivetrain is less well advanced, with 2015 the most likely potential production date.
Sources say it is possible that both of these systems could be fitted to the next-generation NSX, also expected in 2015. The mid-engined supercar will use the all-wheel drive system in conjunction with the electric motors housed in its front wheels.
Super-handling all-wheel drive
This Accord prototype uses a new 3.5-litre, direct-injection, V6 engine upfront, driving the front wheels through a new, wide-ratio, seven-speed dual clutch transmission. This ‘box also incorporates an electric motor of ‘at least’ 30kW power. Driving the rear wheels is a pair of 20kW electric motors, powered by a lithium-ion battery pack, which is charged by the electric motor inside the gearbox. Honda claims that this drivetrain also offers the performance of a V8 engine and the fuel efficiency of a four-cylinder engine.
SH-AWD not only offers all-wheel drive, the twin electric motors driving the rear wheels can be manipulated to help the car steer more keenly into bends. On a right hand bend, the motor driving the inside wheel can have its torque output reduced and the motor on the outside wheel has its torque output increased. The effect is to steer the whole car more aggressively into a bend as well as delivering the advantage of all-wheel drive.
On Honda’s tightly drawn handling circuit, the SH-AWD was not overly impressive in terms of improving handling. While the torque tweaks may have helped the car enter a corner more fleetly, while rounding the bend the Accord felt like any large, front drive saloon. Prolonged hard cornering left the steering feeling vague and disconnected, with a good quarter of free-turn at the rim. And as the car straightened up out of hard bend, the whole chassis betrayed the sudden unloading of forces with a slight shimmer.
While this new drivetrain is a clever way of providing V8-levels of performance, hybrid assistance and all-wheel drive, it does not particularly enhance the handling of this big, front-drive, Accord. However, fitted into a mid-engined car, with the front wheels driven by the electric motors, it could provide a very intriguing basis for a new NSX.
Precision all-wheel steer
The second Accord prototype was fitted with a much less complex, and rather more familiar, technology. Rear wheel steering was used by Honda in the 1980s, but this new set-up is electronic rather than mechanical and is a lot more sophisticated in its operation.
The Accord’s multi-link rear suspension has the toe control links replaced with an electronic actuator. Both hub carriers are mounted in such a way as to allow the rear wheels to be steered in either direction by up to 2deg. The rear actuators use information from the engine, electric power steering and the vehicle stability systems to decide by how much and in what direction the rear wheels should be steered.
Although rear-wheel steering has well-known advantages, such as making high-speed land changes safer, this system can also toe-in the rear wheels during braking, greatly improving stability.
On Honda’s handling circuit, the system was a revelation. Even though the Accord is a large front-driver with a V6 engine in the nose, it handled the very long, tight, bends like a rear-driver. As well as allowing the driver to take the corners at high speed, understeer was all-but eliminated.
Even under hard acceleration, the steering remained extremely accurate, making it possible to place the inside front wheel precisely on the inside edge of the track, even following the changes in radius. The Accord also remained remarkably stable coming out of bends as the car’s weight shifted.
It’s not yet clear whether this rear-steering could be combined with the rear-drive layout of a future NSX, but there’s no doubt that this new-generation electronic system is extraordinarily effective. Retro-fitting it onto the 2015 Civic Type R would, however, be an expensive job: Precision All Wheel Steer can only be fitted to multi-link rear suspensions and the Civic family uses a beam axle.