Saturday, June 30, 2012 - 07:20 pm, by: Wayne Womersley(A49kidx)
Hattori Yoshi talks to the engineers responsible for the Soarer, Piazza and Datsun Leopard.
TAKING THE CLINICAL APPROACH WHEN THE Japanese car makers started talking about turbocharged engines the Ministry of Transport shiny bums told them not to be so irresponsible. Go away, they said, and make your engines more economical instead. This, a 100 km/h maximum speed limit, a large proportion of roads unsuitable for fast motoring and an agreement whereby the manufacturers are supposed to ensure their cars will not exceed 180 km/h, has not exactly been the best atmosphere in which to produce sports cars. But now, within months of each other, Toyota, Nissan and Isuzu have launched three of the sportiest cars to hit the Japanese market since the RX7 and the original 280Z. Cars which aspire to continent-covering ability; cars which had BMWs, Mercs and Opels as their bench¬marks; cars which are boldly adventurous in their use of new designs, components and ideas. Cars which are, on the surface at least, very un-Japanese. Now the Piazza and Soarer, featured in this issue, and the Leopard (see WHEELS April '81) do not use turbo engines — despite some pretty heavy work going on in that field in Japan at present — but in all other respects the new cars must have given the men from the ministry apoplexy. So how did designers whose business up to now was making bread and butter cars, whose techniques owed more to copying than original design, ever manage to get into production cars which, if not exactly 100 percent competitive with the best, are different and thought provoking? Kazumasa Takagi, senior project engin¬eer on the Datsun Leopard, had a bit of a head-start since he was involved in the design of the 280ZX. Takagi says the target with the Leopard is the 'specialty six-cylinder' market. He admits that before he started on the car he went to the Frankfurt Show and saw the Opel Monza — a sort of Commodore coupe — which impressed him. Clearly, the styling of the Leopard is inspired by the Monza, even though those aggressive soft-faced bumpers give the car an American look. Takagi says he studied European and American design for many years. 'I used to read Automobile Engineer from England, ATZ from Germany and SAE Journal from the USA — they were my teachers,' he says. The aim with the Leopard was to match the 280ZX in handling but incorporate a better ride and more refinement. Takagi used a BMW Seven Series car to compare ride, noise, vibration and harshness, and a Porsche 924 for high-speed stability. When it came to the suspension and steering, Takagi and his team had to use Bluebird components, since the Leopard is based on the Bluebird six-cylinder underframe (a US model called the Maxima). However, all the settings were changed and a self-leveling system was added at the rear. Significantly, Takagi says they don't measure spring frequencies any more. Once they have an approximate match, they fit different springs and dampers until they get the ride and handling right on the test courses — and they have courses for high speed running, handling and for rough track simulation. The man behind the Soarer is Toshihiro Okada, chief engineer. He says that with the Soarer he wanted to compete with the best European GTs, and on paper he has succeeded. After all, here we have a car with a 127 kW six-cylinder twin ohc 2.8 litre engine, five-speed manual gearbox, all independent suspension, power assisted rack and pinion steering and a (claimed) drag coefficient of 0.36. The style of Okada and his team clearly differs from that of the Nissan engineers. They seem to have been more analytical and less dependent on the seat of the pants. To his credit, Okada rejected the use of the Cressida underframe because that would have left the engine too far forwards, with too little weight on the rear wheels. So, they designed a new underframe, in which the engine is farther back. As part of the Soarer's development, Okada's team analysed a lot of cars for drag, front lift, and yaw — drag when the car is at an angle to the wind. Okada wanted good results for all three parameters, since tests showed that only the Porsche 924 and Lotus Europa had low coefficients for all three. To see how cars perform in side winds, Toyota uses a side wind generator. The car is driven at 100km/h past a 20m/s wind blowing through a narrow area, and 40 m afterwards the angle and deflection of the car are noted. The driver is not allowed to correct. The Soarer is alleged to do well here, as is the front-wheel drive Audi 100 and Porsche 928. The Mercedes-Benz 350SL and Leopard were not so good, says Okada, with a deflection of about 1.5m and an angle of five degrees; the Soarer's figures were approximately 1.1 m and three degrees. It is worth noting that just about the worst car measured was the Toyota Starlet. Okada admits that Toyota's understeer too much. 'The suspension system must be ahead of the engine,' he says. 'I wanted to make the Soarer as neutral as possible with good high speed stability.' He illustrated this graphically by showing the desirable mild understeer changing gradually to oversteer. And we all thought the Japanese didn't know what understeer was! Although the Soarer is being sold only in Japan at present, Okada is keen to see it in Europe, with different cams to give more power. He sees the car as a competitor to the BMW 635 CSi and Mercedes-Benz 450SLC, and it was to appeal to users of these cars that Okada adopted a three-box design. He sees the customers as mature, wealthy and with an interest in fast cars. And he is entirely serious. When wheeled out on to the street, the Isuzu Piazza is a visual tribute to the genius of Giorgetto Giugiaro and his men at Ital Design. If anything, the Isuzu engineers were overawed by the design and seemed mesmerised out of any attempts to change it so it better suited their need. Osamu Sakauchi, in charge of the Piazza project, emphasises that the styling was the top priority — they had to maintain the look Giugiaro had created at all cost. The costs to the Piazza, as I've already reported, are a long nose which you cannot see from the driving seat, and an engine placed right between the front wheels which gives a front/rear weight distribution of 58/42 — not good enough for a car whose priorities are meant to be road holding and handling. Sakauchi says that a longer wheelbase — to even up that distribution — would make the car less responsive, and the way to improve matters would have been to move the front wheels forwards a little. He argues that to obtain a certain turning radius you need bigger lock with a long wheelbase. That is true but the effect is marginal, and in any case it can easily be compensated for by a change in the steering ratio. Sakauchi's changes to the Gemini suspension have reduced the harshness, but have not improved the control of the rigid rear axle. Faced with an almost constant barrage of abuse about Japanese steering systems, Sakauchi's decision to use the Bishop variable ratio manual rack and pinion steering, and as an option the Bishop rotary valve powered rack and pinion, seems inspired. No other volume maker has had the courage to use it. Giugiaro wanted to use an analogue electronic display for the Piazza's instruments. Isuzu went for a digital system, putting fashion before ergonomics, and tried to get an inclined bar display in to meet the Giugiaro concept. Indeed in this we find a trace of the weakness that has plagued the approach of Japanese designers. They still do not have the courage of their convictions; the strength to hit on a solution, develop it and stick with it. Instead they bend to the breeze of fashion — for fear that their company will be left behind. And with company loyalty the way it is in Japan that is a very real fear, in the minds of everyone who works for the all-important Company. The men behind Piazza, Leopard and Soarer are not enthusiasts in the way that engineers at Jaguar, Ferrari and Porsche are. And their companies are-not steeped in a tradition of high performance cars. Sakauchi, Takagi and Okada have produced their new sports cars clinically, and there are many who will maintain that cannot be done successfully. Sports cars need the human touch ... With these three cars the subjective view would have told the designers that the digital instruments, by and large, are a nonsense; they look good in the showroom but are impractical on the road. It would have told Mr Sakauchi that his Piazza really should have better weight distribution and better visibility from the cabin. It would have told Mr Okada that his Soarer should smooth out the bumps better and have a more flexible engine. And the subjective approach would have left Mr Takagi in no doubt as to what his car is crying out for — a turbocharged two-litre with around 105 kW. That would make the Leopard 300 mm shorter and 100 kg lighter — and turn it into a real 280Z for the '80s. Maybe, though, the ministry shiny bums meant what they said about fuel economy...
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