MAZDA 757 & 767. In 1983 Mazda put its twin rotor type 13B engine into a purpose-built type 717C

In 1983 Mazda put its twin rotor type 13B engine into a purpose-built type 717C sports-prototype chassis, most notable for its novel aerodynamic approach. A two car team was entered in the newly constituted Group C Junior (later C2) category, 12th and 18th overall and first and second in class resulting.

For 1984 Mazda representation ex-panded to four cars; two 727C works chas-sis (developments of the stubby little ma-chines of the previous year) plus a pair of American-entered Lola T616s. All were running the 13B engine and were entered in the C2 class. By the finish Mazda engined cars held first, third, fourth and sixth in C2 with the Lola class winner tenth overall. In 1985 two 737Cs (evolved from their prede-cessors) were third and sixth in the C2 class, 19th and 24th overall, giving Mazda a 100% finishing record in the C2 category.

For 1986 a new triple rotor type 13J engine was developed and a two car team was entered in the IMSA GTP category. The chassis, to a design by Briton Nigel Stroud, had an aluminium honeycomb monocoque with a carbon fibre top section while the engine was carried as a semi-stressed member. Rear suspension was by rocker arms, the front was pullrod and inboard coil-spring/damper units were fitted all round. Cast iron ventilated Brembo discs were mounted on the hubs, operated by single calipers. Twin water and oil radiators were situated on the monocoque behind the line of the doors through which air was ducted to them. Hot air was vented upwards over the tail ahead of the rear wheels. The bodywork of carbon fibre with Kevlar reinforcement was distinguished by a smooth rounded nose with small splitters at either edge, the centre section being left open to induce airflow beneath the car for the ground effect underbody. A twin boom tail section was surmounted by a full width aerofoil sup-ported on two shallow fins with an additional central strut.

The engine was formed from three 654cc rotary units which under the current equivalency formula of multiplying by 1.8 gave a displacement of 3531cc.

The power output was quoted as 450bhp at 8500rpm The transmission was a triple plate Borg and Beck clutch in a Mazda bellhousing mated to a Porsche differential and an in-verted Porsche five speed gearbox.

In the race the legendary Mazda reliability was nowhere to be seen, both cars suffer-ing terminal transmission failures. Ken-nedy/Galvin/Dieudonne climbed as high as thirteenth but went out after eleven hours while Yorino/Katayama/Terada retired af-ter four hours. Technical problems led to the abandoning of a planned turbocharged engine so Mazdaspeed returned to Le Mans with two normally aspirated 757s in 1987. One chassis had lighter bodywork and a lightened engine, the other was one of the 1986 unchanged cars. Yorino/ Katayama/Terada qualified 27th in the new car with Kennedy/Galvin/Dieudonne 28th, but a super-reliable run in the race by the European crew gave them a seventh place overall finish and the GTP class. The Japa-nese trio had been in tenth place overall at the two hour mark, but unfortunately an engine failure caused their retirement a short while later.

A single 757 appeared in 1988 providing back up for two new 767 cars which were similar apart from having four rotor engines, and also ran in GTP. Despite being five seconds slower in qualifying the older car finished ahead of its newer team mates in 15th overall driven by Terada/Kennedy/ Dieudonne and again won GTP .

MAZDA

757 - 1986 Honeycomb monocoque Suspension: pull rod front rocker arm rear Engine semi-stressed Porsche gearbox Ground effect car

3 rotor = 3.5 litres Alloy unit Fuel injected Unblown 450b.h.p.