Mazda Rotary turns 50 – R100 Review

Our rotary retrospective continues, with a Wheels review of one of Mazda’s earliest rotary road cars, the R100 coupe.

Mazda Rotary turns 50 – R100 Review

From the early days of Mazda’s rotary love affair comes Wheels mag’s August 1969 review of the R100 coupe – the first two-door rotary-engined car to be sold in Australia, with a price of $32,195 in today’s money.

With a glacial 0-96km/h time of 13.5 seconds and a quarter mile stat of 17.6, it’s incredibly slow by today’s standards. Back in the day, however, we thought it was a nifty piece of technology that showed plenty of promise. Here’s how we rated it back in 1969:

The most disarming character of the Mazda R100 is its ordinary-ness. After our 1000 mile pre-release test, the fact that the powerplant was quite revolutionary seemed mundanely unexciting.

The R100 is a technical adventure. It breaks new ground in automotive technology  but for those game enough to try a pioneer’s boots, the adventure will have little hardship.

In three days and a thousand miles we tried the R100 in every situation. Commuting, inter-city tripping, bush track pounding and test track revving. It ran faultlessly, smoothly, quickly and quietly; it used some oil and was quite heavy on petrol in conditions of no let-up; we were sorry to hand it back to Westco Motors, the Australian concessionaires.

Mazda R 100 Rotary Diagram Jpg

We think the R100 will prove endearing  personal transport with little kick-back or trouble from an engine which, let’s face it, nobody knows anything about out here, yet. It could be another Mini or it could die hard like two-stroke Goggomobils, only time will tell.

Both engine and car have their separate problems but as a unit it offers for the price as much in performance, comfort and handling as any of its competitors.

The R100 is basically a Mazda 1200 Coupe with blackened grille, round tail-lamps, bonnet louvres and appropriate badges. Inside there is a new aircraft-look dash console while underneath springs rates have been upped and bigger 14 inch wheels shod with radials fitted.

The four speed gearbox and rear axle remains quite conventional. The big news is the twin-rotor 110bhp rotary engine.

Simply, the rotary is an Otto-cycle, four stroke principle of converting heat energy into mechanical energy by induction, compression, ignition and exhaustion of gas in an enclosed chamber. This is achieved by a three lobe rotor that revolves eccentrically in a figure-of-eight chamber (the epitrochoid). Seals on the rotor’s three apexes form separate chambers as they contact the walls and a variation in chamber size as the rotor revolves gives the compression necessary for ignition.

Without delving further into the Wankel engine’s technicality, a reference to diagrams of the four stages will present a clearer picture.

The Wankel engine has taken over 20 years to develop. Conceived in the 1920s by Dr. Felix Wankel the principle was not further studied by Wankel until 1950. The advantages of a Wankel engine are simple. There is less internal power loss because there is no reciprocating motion and hence it follows there is less vibration. With only one major moving part the structure is simpler and easier to overhaul because there are less parts to wear.

There is no power-draining valve train gear. The final outcome is there can be greater power output for smaller overall engine size with greater smoothness and lower noise level thrown in.

With the support of NSU, Wankel developed the engine to the point where it was a practical power proposition. In 1958 the aircraft corporation Curtiss-Wright received a manufacturing licence followed by Toyo Kogyo of Hiroshima in 1960. NSU had themselves pioneered the rotary engine in production sports coupes, but it is Toyo Kogyo who has backed the dream engine to the stage where it can be produced for international markets at a competitive price and with competitive performance.

By development of first a single rotor, then double and multi-rotor engines, Toyo found reliable power for their Cosmo 110S sports coupe (shown in Australia in 1967, and then billed for a $6000 market), and more recently the Mazda RX85 and RX87. The rotary experimental 85 was later destined to become the R100 and now appears on the Australian and Thai markets; the first public sales outside Japan.

The RX87 (now R130) is based on the Mazda 1500 Luce body, with every conceivable luxury. Power output of the R100 is upped to 128bhp for the R130. The R130 should be seen in Australia before the end of 1969.

Seals and rotor bearing have been the main source of concern in development of the rotary. Obviously positive gas sealing in a chamber of only 52cc is imperative. At the same time the wear rate on a lobe seal rotating at 7000rpm in constant contact with an immobile wall is considerable. Toyo put in considerable research and came up with a carbon based seal that showed less than a few tenths of a millimetre wear after 1000 hours’ continuous running.

Because the rotor runs eccentrically, the centre bearing loads at constant high rpm are heavy. Again Toyo has achieved 6000rpm – unlimited time as the standard for the Mazda rotary.

How does all this go in practice? Smoothly, is the operative word. As a baby GT car, the Mazda rotary is without peer for producting effortless touring power. After putting away some very reasonable averages over a give-and-take highway, we are convinced of the R100’s potential as a distance easter, a true virtue for Australian travel.

In city work and away from the lights, the R100 has little real, hard-hitting torque of say the Morris Cooper S. Higher in the rpm range (4000 to 5000rpm) at 80mph touring speeds, there is sufficient torque to stride even steep highway pinches without losing speed.

Fuel consumption is on par with performance and although we achieved 25mpg overall, the gauge did fall at the rate of 19mpg over one section where the R100 fairly guzzled the miles. A small fuel tank (8.8 gals) straight from the 1200 coupe is ridiculously small for this thirst. A range of less than 200 miles is plain not-on in Australia – that’s a re-fill between Sydney and Canberra.

Large wheels, radial tyres and astriding suspension maintain the image of a baby GT for top end touring is compfortable and quiet despite the short 89 inch wheelbase.

A wider rim would be helpful to better handling as the power can produce unwieldy understeer attitudes where the direction of the front wheels has very little bearing on the car’s direction. In power-off attitudes, the R100 will track better.

Retro: 1989 Mazda NA MX-5 - Roofless for the people

Handling is definitely sacrificed for ride but over rough terrain it is extremely good allowing the big wheels to put all the rotary’s power to ground.

The R100’s brakes still have that certain Japanese heaviness about them but with a hefty push they really work. From near top speed the little car will stop surely with no ominous disc rumbles or un-evenness. Provoked to the point of lock-up, the R100 still remains stable.

Inside the R100 is little different to the 1200 coupe in seats and trim. The centre console is an eye-catching feature with an impressive array of dials and switches.

Ahead of the driver are two large dials for speedo and tacho. The tacho has a 7000rpm warning “beeper” and ignition cutout. A map lamp and green “effects” light preside over the console which houses a clock and fuel, temperature and amps gauges. A warning light takes care of oil pressure. Lights, choke, heater controls, fan, radio, power antenna switch, ashtray and cigar lighter fill the gaps.

The heater provides abundant warmth while to dash extremity vents pour in fresh air. These create considerable turbulence around the rear quarter through-flow vent sections, though the through-flow effect is not sufficient to demist the rear window which fogs up easily.

Control for the two speed wipers and washers is by a column stalk. We are not convinced by this idea as the driver must take his hands off the wheel to twist the switch. Low-high beam is by a pull-pull again action of the same lever and pushing toward the column brings in washers.

A headlight flasher and horn Cortina style would be more acceptable with the wipers back on the dash. The wipers have an uncanny habit of lifting off the screen completely over 55mph. Aerofoils, Mr Toyo, would be a very simple solution.

The lights are excellent with good spread and brilliant penetration. The round style tail lights also give those behind penetrating warning of the driver’s braking-turning intentions.

We think the R100 is a technical experiment that will work. It is well integrated and takes the rotary engine power well to put it among the top desirability stakes in personal transport.


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