Mazda engineered the new MX-5 sportscar for production in just 17 months, its fastest-ever time for an all-new car, reports Julian Rendell.

The open-top two-seater went into production for the US market on May 17, just over a year and a half after the styling was signed off in December 2003. The European models being launched last week started rolling off Mazda's Ujina No 1 plant on July 12, a month after Japanese cars.

"This was a very quick programme," says deputy program manager Nobuhiro Yamamoto, "helped by our simultaneous engineering with virtual engineering for the whole the car."

Yamamoto says the MX-5 is the third all-new Mazda developed under the new Mazda Design Innovation (MDI) process. The Mazda 6 pioneered MDI and the Mazda 5 mini-MPV was the second.

Both those projects took around 24 months, according to Yamamoto. Only the domestic market-only Verisa, a new 'top-hat' on the Mazda 2 platform can match the MX-5's rapid development cycle, said Yamamoto.

MDI centres on a virtual engineering system that holds detail designs, in what Mazda calls 'Datafiles', in a huge database.

This allows product engineers to share detail design information with manufacturing engineers so that factory-build can be prepared at the same time as the car is under development.

As a result, the MX-5 project team was able to hold off the critical move to production tolling until just before the end of 2004, very close to production.

Fundamental platform engineering of the MX-5, however, began in May 2003 when Mazda started testing the new suspension, powertrain, body structure and sub-systems. "Before design sign-off we have the platform designed so we can start testing straight away with our 'M1' prototypes," says Yamamoto.

Although the basic architecture is shared with the RX-8, not a single part is currently common between the two.

However, that will change next year when the RX-8 adopts the MX-5's new, Mazda-designed and built six-speed manual gearbox in places of today's Aisin-built unit.

Despite the individual component set of each model, the two sportscars are built on the same line at Ujina. This is possible because the crucial fixing points for assembly jigs and tools are common.

Ujina is a highly-flexible plant, according to Yamamoto, and the two sportscars also share final assembly with the Demio small hatchback.

All three are assembled on a very short cycle time of just one minute, unusually fast for specialised sportscar models.

The press and BIW facilities for the MX-5 and RX-8 are also highly-flexible. Yamamoto says that with fast-tool change presses, that these lines can switch seamlessly between the two different sports models.

A single body-framing station, where panels are welded into a complete bodyshell, is used for both the RX-8 and MX-5, a considerable achievement since the MX-5 is much smaller and sits on a 250mm shorter wheelbase than the bigger coupe.

Under the skin, Mazda's engineers have also had to cope with the challenges of different legal standards in the MX-5's three main markets of the EU, Japan and US.

As a result, European models have a longer final drive ratio (3.7:1) compared to 4.1:1 for the US and Japanese models, a design change that stems from Europe's stricter drive-by noise test. There is also an extra under-engine noise cover that adds weight to the EU models.

To compensate for the adverse effect on acceleration, European's MX-5's have revised second and third gear ratios.

However, Yamamoto says the EU models remain slightly slower than US and Japanese MX-5s.

Julian Rendell

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