Mazda MX-5 under the microscope

MAZDA'S all-new MX-5 project leader, has revealed some fascinating, but not widely known design and engineering details of the fourth-generation sportscar.

Speaking at the launch of the 2015 ND MX-5, Mazda Motor Corporation MX-5 program manager Nobuhiro Yamamoto gave GoAuto an inside look at the inner workings of the eagerly awaited model. Here are the tastier tidbits.

Development started in 2007 using the RX-8 and previous-gen MX-5 platform, until the global financial crisis saw Mazda's worldwide sales free fall, prompting the company to put its roadster project on hold for three years.

If all had gone as originally planned, a very different ND MX-5 would have been launched in 2012, without the SkyActiv suite of technologies that the car gained after development recommenced afresh three years ago.

Mr Yamamoto explained that the ND has been engineered “from the driver out” in order for his team to hit the size and weight targets set for the vehicle compared to its 91kg heftier and larger predecessor.

Australian-bound MX-5s gain the European steering tune rather than the heavier US set-up because America's relatively straight roads requiring less sensitive responses just off-centre. An approach referred to as building in the ’Sneeze Factor’.

The steering was tuned at Mazda’s Miyoshi Proving Ground near Hiroshima, on Japanese public roads, in Europe and the USA.

Mr Yamamoto explained his tyre preference is for the Yokohama Advan that is fitted to all new-generation MX-5s around the world as it offered the right balance of comfort, balance and dynamics.

The fitment of 15-inch wheels was heavily considered but later rejected in favour of the 16-inch for 1.5-litre variants and an inch larger for the 2.0-litre performance flagship.

The MX-5’s solenoid boot release above the number plate saves weight and preserves aesthetics, but ends more than 25 years of the release lever being positioned between the seats.

While all gearboxes in the latest generation Mazdas are in-house SkyActiv Drive units, the 1.5-litre variant’s 6-speed automatic is built by Aisin in Japan - a company owned by Toyota.

The exhaust system features a synthesised sound with three different ranges depending on engine speed – ‘low’ for a light/crisp noise, ‘medium’ to evoke a beating heart, and ‘high’ for a soaring orchestral note says Mr Yamamoto.

Mazda’s engineers deleted the glovebox in order to significantly increase the amount of passenger knee and legroom over previous models, but additional storage is provided in the bulkhead behind the seats.

From the driver’s seat, the shape of the bonnet and front mudguards is meant to be reminiscent of the original model's pop-up headlights, that were binned for the second-generation to boost pedestrian impact protection.

Mazda’s designers briefly considered developing modern pop-up headlights now that they can be engineered to satisfy the US pedestrian impact regulations, but were ruled out as too complex, heavy and obstructing for the driver.

A ski port was also considered to help boost cargo-carrying practicality but was later dropped so that the fuel tank could be safely isolated from the cabin.

Mazda says it had costed the new MX-5 as a viable go-alone project before Fiat Chrysler Automobiles came on board with the upcoming Fiat 124 Spider variant, which shares the underpinnings of the Japanese car.

For now, the MX-5 is the only SkyActiv-equipped Mazda without fuel-saving idle-stop technology or a transverse engine, and is the only rear-wheel drive vehicle in the line-up.

Mr Yamamoto’s favourite detailing is on the up-spec Roadster GT’s body coloured upper door trims, which appear from the driver’s point of view to spear forward past the inside of the A-pillar, connecting the bonnet line as it falls away ahead of the car.

The latest DJ-series Mazda2 compact hatchback donates its HVAC air conditioning system to the MX-5, but the dinky tool kit carries over from previous generations.

The instrument dials are borrowed from the CX-5 albeit in a rearranged layout with the tachometer taking central position and befitting a sports car.

Adding a spring-loaded mechanism to the manual roof base greatly helps reduce the effort required over past set-ups to lift the item up into place, while power operation was considered way too heavy for the sub-one-tonne car.

There is about a 10kg difference in weight between the base Roadster and its better-equipped Roadster GT sibling.

Mr Yamamoto said several independent companies were called in during the ND’s prototype stage to design and then propose an aftermarket detachable hardtop.

No reach-adjustable steering column is fitted to any MX-5 because of the unacceptable weight it would add, but Mr Yamamoto admits this may change in future models as a lighter unit is under development.

The ND is the first MX-5 to not wear the small oval side indicator that launched with the 1989 original.

The controversial front-end styling is meant to convey a ‘smiling face’, but only if you are at looking at it straight on at knee-height.

Its wheels have a four-stud pattern compared to the NC’s five-stud arrangement in the name of – you guessed it – more weight saving, while the use of aluminium in the folding roof header rail not only saves weight but cuts noise transfer, according to the program manager.

Mazda is using a patented new recyclable plastic for the surprise-and-delight detachable cupholder rim surrounds, which do not degrade in the hot Australian sun.

Mr Yamamoto revealed he co-operated with Subaru BRZ/Toyota 86 chief engineer Tetsuya Tada to help make the latter pair better sports cars, because Mazda believes the resulting competition would grow the market and help foster the next generation of enthusiasts, benefiting the entire Japanese car industry.