ROB MARSHALL TAKES A LOOK AT NEW CAR TECHNICAL INNOVATIONS…
Writing about the latest Honda technology is a little poignant, considering the company’s imminent departure from UK manufacturing. By the time you read this, Honda’s Swindon factory is likely to have been handed over formally to a logistics firm, ending a relationship that started in 1979, overseen by its founder, Soichiro Honda, a real Anglophile.
Looking to its future away from British car assembly, Honda’s current car strategy rests on e:TECHNOLOGY, with e:HEV being the high-voltage hybrid denotation. Despite Honda announcing that the 2022 Civic will be launched with hybrid technology, we see e:HEV on current production Hondas already, including the Jazz, CR-V and HR-V models.
While the next-generation Civic’s specifications have yet to be revealed, the following information applies to the current Jazz. e:HEV comprises a 1.5-litre, 72Kw petrol Atkinson cycle engine, with an impressive maximum engine thermal efficiency
of 40.5%. Yet, even the best combustion engine is far from efficient, hence the scramble to high-voltage electrification, and so e:HEV combines the engine with two electric motors: one for electricity generation (70kW), the other for propulsion (80kW ).
The engine powers a generator that charges a battery pack but it can be connected and disconnected mechanically from the drive wheels with a clutch. This means that the engine cannot stray from its most efficient RPM by wheel speeds.
When operating in ‘pure EV’ mode, the battery pack provides sufficient power for the propulsion motor to drive the wheels in low-load conditions with the engine switched off. Hybrid mode means that the engine is running to provide more power to the battery so that the propulsion motor receives sufficient current. The engine can also drive the road wheels directly, when the connecting clutch is closed. This last point makes Honda’s system different to a Series Hybrid (such as a range extender), where the engine’s sole purpose is to charge the battery.
e:HEV has more in common with Series-Parallel hybrids, a layout that is used on other cars, although the Honda e:HEV employs neither a gearbox, nor a planetary reduction gear in the transaxle, to keep drivetrain friction losses to an absolute minimum.
Silence is certainly not golden in every situation. Devoid of noise associated with internal combustion, EVs are mandated to emit synthetic sounds to warn pedestrians of their presence. Yet, Nissan discovered another issue. After finding that 51% of parents undertake special car journeys to lull their infants to sleep, 62% of which do so more than once weekly, it also discovered that successful snoozing was caused not by vehicle movement but, predominately, by the hypnotic soothing frequencies from internal combustion engines.
According to Nissan’s Noise and Vibration Development Manager, “Although an electric vehicle, like the Nissan LEAF, is a more environmentally considerate choice for ‘dream driving’; the quiet soundscape of an EV might not be as effective as internal combustion engine (ICE) cars. Combustion engines transmit a sound frequency, a combination of white, pink and brown noise – varied in tone – creating an orchestral soundscape that is especially soothing and comforting to young children.”
So, in collaboration with Sound Designer and Sleep Coach, Tom Middleton, Nissan has created ‘Dream Drive’, the world’s first ‘zero-emission lullaby’. Consisting of five three-minute audio tracks, the soundscape is played through the stereo to mimic the peaceful audio frequencies of a combustion engine.
The recordings include all of the elements that might be encountered on a typical drive cycle, including sounds emitted from keys, direction indicators, air conditioning, engine start, interior fabrics and, of course, those associated with accelerating and decelerating.
Dream Drive is available on Apple Music, Spotify, SoundCloud, YouTube and Deezer. It can be streamed via: https://lifetracks.lnk.to/NissanLEAFDreamDrive.
While not yet launched at the time of writing, Mercedes has high hopes for its forthcoming SL. Developed by its AMG high-performance division, the car drips with technology, boasting mild-hybrid six and eight-cylinder engines and including four-wheel drive for the first time in the model’s history – a heritage that stretches back to the gullwing-doored 300SL of 1952.
Interestingly, the original’s gullwing doors were not created for marketing reasons but were an engineering compromise that resulted from the original spaceframe structure. Although Mercedes-Benz did its best, with the materials available at the time, to produce a lightweight and stiff structure, its shape dictated that conventional doors were unfeasible.
Yet, the latest car is not bound by such restrictions and its new bodyshell (pictured alongside the 300SL’s original spaceframe) boasts a variety of materials. For example, aluminium underpins the main floorpan chassis members. Magnesium reinforces the fascia panel support and the front end is made from a glass fibre and carbon mix. As the SL will be available solely with a folding fabric roof, the high-strength tubular steel windscreen frame also forms part of the rollover safety system.
Interestingly, cast aluminium is employed in certain areas, through which significant impact forces are transferred in an accident. To save weight but not crash performance, cast panels can have their thicknesses varied in production, so parts of the panel can be engineered to be more rigid. This may seem pointless but the reward is reduced mass, because the basic bodyshell weighs only 270kgs. Mercedes-AMG also claims that the body is 18% stiffer than the outgoing AMG GT Roadster and between 40 and 50% more rigid.
Limited Slip Differentials on performance cars of the past made a decent effort of discouraging maximum torque to be sent to the wheel with the least grip. By being limited, however, they were not perfect. Not only did a loss of grip between the trye and road have to occur before the system reacted but also ‘LSDs’ could only divert a proportion of torque available.
Naturally, electronics, CAN bus communication and refinement in clutch plate technology has seen a new breed of differentials evolve. Many manufacturers refer to these types as ‘torque vectoring’ units, which can be proactive and direct virtually all available drive to the wheel(s) with the most grip.
The upcoming 2.5-litre 400bhp RS 3 is reputed to be the last non-high voltage Audi performance model and, possibly, the last one to use the renowned five-cylinder petrol unit that has origins in the mid-1970s. The RS 3’s torque splitter rear differential unit is interesting, because, while it retains a crown wheel and pinion, it loses the traditional gear carrier assembly and replaces the bevel gears with two wet clutch packs and associated electric actuators. These features enable it to transfer all of the power available to the rear axle (a maximum of 50% total torque) to a single wheel.