The Mazda R100 was released in June 1969 and was
one of the first Mazda vehicles equipped with the rotary engine. It was
available as a coupe only, and was based on the 1200 coupe which had been on
sale for over a year. However instead of the 73hp 1200 engine, the engine was a
revised 10A similar to the of the 110 Cosmo. For Japan and Australia the 10A was
rated at around 100hp.
Back in the late 60's, the term 'Sleeper' was still in vogue. A 'Sleeper' could be described as a wolf in sheep's clothing, a machine that looked ordinary but performed exceptionally. In 1969 Mazda had the best example of a Sleeper, it was the R100. There were no go-fast stripes. The badge work was restrained. In fact, apart from a blacked out grille there was virtually nothing to suggest any additional dose of sporting character.
The 110S was the car that declared Mazda's presence as an innovative car maker. But it was the little R100 that translated this into mass production. The R100 proved that Mazda was serious about its rotary engine. This was not merely a piece of impressive high technology to be plumbed into pricey sports cars; rather it was a genuine alternative to the traditional reciprocating engine.
A quarter mile best was reported of 17.8 at 74mph. It was probably slower than the factory time of 16.4 due to the lack of familiarity with the rotary's characteristics. Still this performance was enough to be nervously close to the 'Big Boy' league. In 1969 a similarly size car was pushing to crack 21 seconds. So inevitably the diminutive R100 found itself being compared with performers like the Holden Monaro, Ford Capri, Valiant Pacer, Ford Cortina GT, Fiat 125 and later on the Holden Torana GTR. The Toyota Corolla Sprinter and the Mini Cooper S couldn't get near the Mazda's performance and couldn't be considered true rivals.
Out of these cars, the R100 was the least assuming externally, while being one of the quickest. It could run to a genuine 175km/h. The Pacer and GTR could match it's acceleration but were short on top speed, (about 168km/h in both cases), while the Fiat and Cortina GT were well behind (158 and around 150km/h respectively).
Apart from the performance provided by the rotary engine, the R100 was also superbly built and finished, in the style that Australian buyers were beginning to take for granted in Japanese cars.
Alongside a current 323, the R100 would look rather small. With it's overall length of 3830mm. It was narrow too (1480 mm) - not much wider, in fact, than it was tall (1345 mm). Throw in the standard issue skinny 145/SR14 radials on narrow rims and the high ground clearance of 160 mm and you can see why the R100 along with its 1200 siblings managed to have a tip-toe stance while standing still.
Overall dynamics were definitely the weakest aspect of the R100 though. MacPherson struts were used at the front in what was already the conventional front end design. The rear suspension was unsophisticated semi-elliptic (leaf) arrangement. The ride was quite reasonable for a small car but there was a tendency to bounce over choppy surfaces with the leaf‑sprung rear end prone to jumping around over bumps inconveniently located in the middle of corners. There was plenty of body roll. Brake wise, there were discs up front and drums on the back.
There was a redline of 6500rpm and a cutout on the carburettor's second barrel at 7000rpm, although much higher revs can be achieved with a stock engine. Back in the R100 era, the engineers were justifiably worried about durability, particularly of the rotor tips and it was this concern that led to the lowish limit.
As for motorsport, Mazda raced its R100 with blind ambition. Mazda was, after all, very proud of its new rotary engine, and in July 1969 the factory entered two R100s in the famous Spa-Francorchamps 24-hour, a production-type race where many of the world's manufacturers entered to compare product against opposition product. The Spa R100s ran with their Cosmo type all-aluminum 10A engines. By this stage Mazda's 10A peripheral ported engines were capable of 200+hp, but the Spa engines were held to around 187hp for endurance reasons. Still the small R100s put in a big performance to finish a very respectable 5th and 6th overall behind factory 911s Porsches. For the 1970 Spa-Francorchamps race, an R100 again came 5th outright. Locally, R100s were tried at Bathurst and a few touring car rounds but didn't do very well.
During its 2.5 years on sale, the R100 went through more mechanical changes than any other rotary after it. The main factor behind this was the factory's uncertain direction with its rotary powered vehicles. The R100 was a prototype vehicle being mass produced; therefore, throughout its model run it was updated regularly as Mazda engineers improved upon the rotary engine. Many of these changes affected the R100 mid-model run. Today manufacturers generally wait for the next model change, for example: the Series I to Series II RX-7.
The R100 can be divided into a Series I and II with the date separating them to be about mid 1970. The interesting thing about the R100 is that some Series I are fitted with Series II parts and vice versa. Production uniformity didn't really start until the RX-2. It is also generally considered Mazda produced the R100 only as an interim model before the RX series started, which was designed to fit a rotary.
When looking for a genuine R100, the chassis number must start with M10A. The 1200 will be STA, and the 1300 will be STB/C. Notable rotary/piston differences are:
GRILL: the R100 has slightly different design and is painted black compared to being chromed. R100 also has small rotor in the centre.
BONNET: the R100 has a raised section with louvers cut into it.
TAIL LIGHTS: The R100 has round lights compared to the 1200/1300 square type.
SUSPENSION: the R100 had a different style compared to the 1200 but changed to be the same with the 1300. The spring pressures and rates were changed with the R100 using 103lb/in and the 1200 71lb/in. R100 received an extra leaf in the rear springs.
WHEELS: R100 received 14-inch wheels while piston models rolled on 13-inch wheels.
BRAKES: R100 came with 9.6 inch Girlock disc and pad set under 14-inch rims.
When Mazda first offered the car for sale, the starting price was $2790 and inflated by only $100 through its showroom life span.
Years Available: 1969 to 1971
Engine: 10A (982cc) twin rotor (2 x 491cc) Carby
Transmission: 4 Speed Manual Only
Power (Approx.): 100hp (74.5kw) @ 7000rpm
Torque (Approx.): 100 Lb/Ft (135.5Nm) @ 4000 rpm
Weight (Approx.): 805 kg
Chassis Prefix: M10A
Original Cost (Approx.): $2790 AUD