Mk1 Article...

[TheNissanMan]

In June 1984, Toyota unveiled the best sports car it had ever made, MR2. That’s not the name of a man, it actually meant "Mid-engined, Rear-wheel drive, 2-seater". It was the first mid-engined Japanese car.

Flyweight mid-engined sports car was not a new idea. As early as 1972, Fiat pioneered that with the ground-breaking X1/9, which was still on sale in Europe in Bertone’s Badge when MR2 was born. Despite of great design and packaging, the little Fiat was so lack of punch and a proper build quality that it never won overwhelming applause, leaving Toyota a big black hole to fill in. Combining multi-valve technology, Japanese build quality and the packaging cleverness that learned from X1/9, Toyota MR2 became the first truly world-beating flyweight mid-engined sports car.

Development

MR2 was unmistakably an in-house design. However, Lotus also had a hand in it. In prior to the 25% takeover by Toyota in 1984, Lotus had already been providing engineering consultant service to the Japanese no. 1 car maker, especially in the field of multi-valve technology employing in the 4A-GE engine. Since 1976, Lotus has been using 16-valve four-cylinder engine in its road car Esprit and was considered to be the leader of this field. The money-seeking Lotus transferred such technology to Toyota, resulting in the 130 hp (JIS) 1.6-litre dohc 16V powering the Corolla AE86 coupe. This engine was carried over to the MR2, mounted transversely amid-ship without much alteration.

Lotus also played a role (if less influential) in the tuning of the chassis and suspensions. Engineer Roger Becker was sent to Japan to conduct some tuning to the early development car and through which trained the Japanese engineers handling know-how. However, the production spec. was finalised by Toyota itself. The all-strut suspensions were donated by the Corolla.

The first prototype was shown in the ’83 Tokyo motor show in the name of SV-3. After reshaping the body a bit, the production MR2 (internal code AW11) went on sale in Japan in June 1984, although most other countries got it in the next year. It immediately won Japanese Car of The Year award.

The Car

Calling it an engineering masterpiece is never exaggerate. I can’t think of any car as all-round yet as sensational as the first generation MR2 (AW11), not the second generation (SW20), not even the current 3rd gen MR-S or Mazda MX-5, not its arch-rival Honda CRX, not Lotus Elan (no matter Mk I or Mk II).

The most appreciated aspect was handling and ride. Technically speaking, the first MR2 had a perfect package - compact dimensions, rigid chassis (if not for the later T-bar version), low polar moment of inertia due to the mid-mounted engine and 45-55 front-to-rear weight distribution (I always consider that even better than 50-50 in realistic conditions, that is, braking into corner, powering out of corner etc.). In reality, the tuning made it even better than paper suggested. It’s very neutral and responsive to steer. The unassisted steering was direct and full of feel, flowing streams of information from black top to hands without the slightest corruption. It felt somewhat like today’s Elise, in other words, nimble. Only at the limit it would understeer a little bit to provide a secure control. Back off, it would return to neutral. The AW11 was really a joy to play.

Simultaneously, ride was surprisingly comfortable for a sports car and actually matching the contemporary family sedans. By the way, that was the tradition of Japanese sports car. Another tradition was that every controls were precise to operate: the unassisted steering was well weighted all the time other than parking, thanks to the lighter nose. The gearchange was super-slick, unlike many mid-engined cars. All pedals were adequately weighted and travelled. On the other hand, the cabin was spacious for 2 (of course for 2), with generous head and foot room, plus supportive bucket seats, good driving position and ergonomics (unlike X1/9), first class visibility due to the big windscreen ...

No wonder even the most critical European car testers couldn’t help falling in love with the little Toyota sports car. (of course, the more Japanese-car-friendly American also loved it) Autocar commented it "A classic of the making", "A class of its own" and "Original MR2 handles better than a 328GTB"; Fastlane magazine (another died British magazine) called it "Handling, roadholding, ride are sensational, performance strong. Decisive leader among affordable exotics." Enough ?

The engine and T-VIS

Right now, we still haven’t really touched the 4A-GE engine. It was the first mass produced 16-valve engine in the world. In Corolla coupe AE86 as well as the MR2 AW11, it displaced 1587 c.c., having a bore slightly larger than the stroke at 81.0x77.0 mm. Cast iron block and alloy head on which twin-cam was mounted. Max. output was 122 hp and 105 lbft (DIN) for Europe, or 112 hp and 97 lbft (SAE) for USA because of catalyst and other mild changes for emission control. In domestic market, it was rated as 130 hp and 110 lbft (JIS Gross) but later re-rated to 120 hp and 105 lbft measuring as NET output.

The whole engine and compact 5-speed gearbox were transversely mounted in front of the rear axle. The heavy Battery was located in front of and above the transmission, thus also reduce polar moment of inertia. Due to the tight wheelbase, the fuel tank was installed in the transmission tunnel.

Most early 4-valve engines were not good at low-to-middle speed torque, simply because the larger intake area resulted in slower air flow. Especially at low speed, the slow air flow in the intake manifold led to imperfect mixing of fuel and air, hence knocking and reduced power and torque. Therefore 4-valve engine was regarded as strong at top end but weak at the bottom end, until the technology of variable intake manifold became popular recently.

However, Toyota had already found a solution as early as the AW11 / AE86 era. The 4A-GE engine employed a patent T-VIS (Toyota Variable Intake System) to accelerate low speed air flow to the manifold. The theory was quite simple: the intake manifold for each cylinder was split into two separate sub-manifold which joint together near the intake valves. A butterfly valve was added at one of the sub-manifold. At below 4,650 rpm (some sources said "around 4,300 rpm" though) the butterfly valve would be closed so that raising the velocity of air in the manifold. As a result, better mixing could be obtained at the manifold (excluding direct-injection engines, fuel injection always takes place in the manifold).

Article taken from: http://autozine.kyul.net/classic/toyota.htm#2000GT

Date: 25/03/03

There’s a common misconcept saying the T-VIS transformed the engine effectively into a 2-valve one at low speed. In fact, all intake valves always breathed because the sub-manifold jointed together near the valves.

Performance

Benefited by the enhanced low-to-mid range torque, the MR2 was not only flexible to drive but also showed remarkable performance for its days. A contemporary Bertone X1/9 took 10.8 seconds for 0-60 and topped 110 mph. In a sharp contrast, the MR2 normally took 8.0 seconds and topped 121 mph. (Autocar recorded 7.7 sec for 0-60 but the result was hardly repeatable by other magazines. Fastlane’s time of 8.0 sec was more adequate.) The US version was measured as 8.3 sec and 116 mph by C&D, or 8.4 sec and 121 mph by R&D. Apart from Honda CRX, I can’t think of any mass production rivals can beat it.

MR2 Supercharger

Two years after launch, in other words, ‘86 for Japan and ’87 for overseas, a supercharged version was added. It was sold exclusively in Japan and the USA.

It was essentially the same engine, with compression ratio reduced from 9.4 to 8.0:1 and added a root-type supercharger with air-to-air intercooler. A mild charge pressure of 8 psi raised output to 145 hp and 140 lbft. As usual, it was the extra bottom-end torque that transformed the car into a hot machine - 0-60 mph was done in merely 6.4 seconds - even though the car weighed 130 kg in-excess of the normally aspirated version.

At low speed, an electromagnetic clutch would disengaged the energy-inefficient supercharger so to save fuel and make idling refiner.

MR2 Supercharger was chosen as one of the 10 Best by Car & Driver in 1988.

AW10

The entry-level of MR2 was bounded in Japan, powered by a 1.5-litre sohc 12V engine outputting 84 hp. It is the only MR2 mated with automatic transmission.

Conclusion

MR2 was the peak of Toyota's success. Until today, no other cars from Toyota received so overwhelming praise from all over the world. Lexus LS400 and Supra might be remarkable, but few regarded them as a clear class winner, let alone a classic. Unquestionably, MR2 is still unmatchable.