1972 Mazda RX-2 RE Coupé

Mazda is relaunching its rotary technology so we took a fresh look at what the only manufacturer who had sales success with this technology achieved in the past.

By Terry Cobham, photography by Greg Vincent

THE ROTARY REVOLUTION RETURNS MAZDA RX-2 A TOUCH OF THE ’70S

In 2023, Mazda plans to start selling a rotary-powered car again. Gone is its penchant for attaching this moniker to something sporty. Instead, Mazda plans to use a small rotary to augment the range of a new small SUV battery-powered vehicle. One end of the electric motor will contain a small single-rotor Wankel motor, to credit its inventor, that will drive the generator and thus extend the range from 100-plus kilometres to something like 600.

The rotary motor to date has been one of those engineering feats that has almost always delivered more promise than anything else.

HITLER’S PART IN THE ROTARY MOTOR

Self-taught German engineer Dr Felix Wankel came up with the idea of an engine that avoided pistons reciprocating in cylinders in about 1924. In his words, it was “a new type of engine, half turbine, half reciprocating. It is my invention”. Wankel was a clerk at a printing works but obviously his mind was elsewhere. He was dirt poor — so poor, in fact, that he could not even afford to be an apprentice. This probably helped shape his political views as well, because he was also an extremely enthusiastic Nazi — so much so, that he had a major falling out with the leading Nazi in his area and was thrown in jail. That jail term only ended when Hitler himself intervened and had Wankel released. He then became an SS Stormtrooper and spent the war years engineering for Hitler.

After the war, the French jailed him for his Nazi activities but eventually he was released and restarted his efforts to create an engine that performed more efficiently and with less vibration than the normal reciprocating motors available.

EARLY BEGINNINGS

He had patented his engine ideas as early as 1929. Post-war, and by 1957, he had manufactured prototypes and licensed his engine design, first to the Curtiss-Wright aircraft company in the US. Debate surrounds which vehicle manufacturer was first to develop a Wankel engine–powered car. It could have been NSU, with a Prinz model. Skoda claims that it was the first with its Wankel-powered 100MB. What is certain is that the first Wankel-engined production car was the 1964 NSU Spider. The tiny 500cc engine gave the tiny car a not-so-tiny top speed of 155kph. This certainly helped get the whole rotary-engine concept noticed. NSU eventually produced the groundbreaking — as well as engine-breaking — NSU Ro80. Sadly, the car failed but by now the rotary engine was stuttering towards a real life.

TOO HOT TO HANDLE

In the following decade, various manufacturers dipped their toes in the water but most found it too fraught to continue. Mercedes, Ford, General Motors, and Citroen, as well as a handful of major motorcycle manufacturers all produced development models. Some managed to get some cars to market for a limited time. Citroen even set up a joint–but–eventually ill-fated engine-manufacturing division with NSU. Citroen produced two different Wankel-powered models, one based on the Ami and one on the GS. The second of those almost tipped Citroen into bankruptcy. Total sales of the two models scarcely broached 1000.

Ford was a part of a project that died at birth, a rotary-powered Mustang. General Motors did produce one Corvette that was rotary powered, and from 1975 until 1977, Holden sold a few HJ and HX Premier models to Mazda in Japan. They fitted the 1.3-litre versions of their rotary to these cars, endowing them with appalling acceleration and even worse economy stats. The sales statistics matched as well.

IF AT FIRST YOU DON’T SUCCEED …

All was not lost for the Mazda rotary motors, though, as Mazda engineers had continued developing the various bits and pieces. A rotary motor consists of a piston that rotates rather than going up and down. The rotary piston is simply a triangle with the corners rounded off. This spins around a fixed gear inside the cylinder block in an elliptical orbit, sort of like a hula hoop going around a waist. Wankel was not a qualified engineer but he knew enough to be able to see what laws of physics and mathematics could be applied to his plans for his motor.

The rotor uses each of its three sides in one revolution. First, the piston passes the inlet port where the fuel is drawn directly into the motor — no valves, just an inlet port. The wall of the cylinder block is shaped to compress the air–fuel mixture against the rotor and two spark plugs fire not quite in sync. This propels the piston on to the next phase where the gases are ejected through an exhaust port, again without the aid of valves. A single-rotor motor has just two moving parts, the piston, or rotor, and the crankshaft, cleverly combining with the shape of the chamber to still manage the essential suck, squeeze, bang, blow.

ADDING ROTORS

Mazda and others had added extra rotors to these motors and single-, double-, triple-, and even quad-rotor versions of these motors exist. Mercedes persevered with a triple-rotor version in its attempts to create a luxury sports car, even testing quad-rotor versions before dropping the project. Mazda did create a quad-rotor version and eventually won Le Mans with its now-famous 787 sports racing car.

The Mazda RX-2 or Capella featured here is a Japanese-assembled and New Zealand–new car. These models, probably only the four-door version, were also assembled at Motor Industries International at Ōtāhuhu in South Auckland. This car was sold new in 1972 so it is a ‘series 1’ version. Over the course of the model’s life, Mazda introduced rolling changes but never really designated the cars with different series numbers. The series numbers are known but not denoted, and small changes like headlight and tail-light design, and bonnet shape are the easiest ways to recognise who’s who in this particular zoo.

FIFTY-ONE YEARS LATER

Kelly Walden bought this car as a project 10 years ago when it had already languished in a container for more than a decade. The car was from the South Island originally. The rotary motor had been replaced by a regular four-pot 1600cc unit. Kelly acquired a rusting ruin and set about what has been a decade-long project for him. He has completed 90 per cent of the work himself, and this has included stripping the car back to bare metal before beginning a complete rebuild. Rusty panels were either repaired or ditched — mostly the latter. The only original panels are the two doors and the roof. Such care has been taken that the bonnet is the fifth he bought before he was satisfied.

Every mechanical part has been restored, rebuilt, or replaced. To look under the bonnet is to see what the car would have looked like as it rolled out of the Mazda plant in 1972 — well, almost. In this case, it looks better. Kelly has made some modifications that trainspotters will notice but essentially this is a restoration.

SMALL CHANGES

Every nut and bolt has been ‘passivated’, which means that it has been ‘decorated with a non-reactive coating’. In this case, zinc. Every piece of metal gleams like new and even if it isn’t original it looks like it. The original air filter — factory colour, of course — complete with new transfers, hides the non-standard 48mm four-barrel Weber carb that has replaced the original Nikki. The double distributors send an uprated spark to their respective spark plugs but hidden inside are new electronic packs that have replaced the points.

SOME NOT SO SMALL CHANGES

The mechanical bits and pieces go on like that. The original brakes are still there, just the pads are uprated. The whole car sits marginally closer to the ground now with both uprated springs and shocks. All rubber bushes have been replaced with Nolathane pieces, so the car is also tighter in that respect.

The motor, which is also mildly uprated, has lightened and balanced rotors, and smaller carbon apex seals. Those apex seals — the part that covers the rounded tip of each triangle section of the rotor at the point that it meets the combustion chamber wall — need to make a friction seal, and they are the parts that caused so many problems for early rotary owners. Some Citroen motors lasted less than a week before they were back for replacement seals. Kelly has also uprated the oil-pump capacity and oil flow around the motor, treating another area related to the unreliability issues these motors were known for.

To assist with the motor’s breathing, he has what is called a ‘full-cut bridgeport’. In simple terms, this means that the holes in the inlet and exhaust chambers have been made so big that they have to have a bridge across them so those apex seals have something to support them as they run across these areas. Imagine what an orange sliced through the middle looks like and the bridge is there where the pith is. The orange itself is just a great big hole that the gases flow through.

The flywheel has also had metal cut away and the clutch is now a heavy-duty version. This means the free-revving motor can really do its screaming stuff. Kelly says that he still has tuning work to do on the motor but it already sounds better than any of those boy-racer rotaries that used to be a part of the Friday-night scene across the motu.

A TOUCH OF THE ’70S

To sit in the car is to go back to the ’70s. It has an analogue dash, of course; switches that stick out from that dash; what looks like a too large and too skinny steering wheel; and the gear lever is just that, a lever. Then there is that noise — like tearing a sheet of calico and a gunfight at the OK Corral all at the same time. When it makes a noise like that, who cares what it handles like? But it really does feel tight and tied down, in a 1970s way, of course. An estimated 134kW, up from an original 97kW, really makes the car sit up — so much so that it will more than just chirp the tyres on an upshift. The motor will spin up to 8000rpm, and by reputation, depending on the bravery of the owner, it will keep climbing from there.

The car has been repainted Aurora White, an original Mazda colour. The interior is almost all brand new, with the seats, carpets, and dashboard all replaced or redone to new. Only the headlining is as it was, and that’s because it is in such good condition that Kelly wanted to keep as a nod to the car’s past. This little car looks better and goes better than new, and must now be one of only a very small handful of these pretty little pieces of 1970s car history remaining.

1972 Japanese interior design, almost mid century, and at the moment nothing is as fashionable as that is again. Owner Kerry Walden and 10 years’ worth of restoration.

Left: The underside is as pristine as the rest of the car, with everything back to new condition

A gauge has been added under bonnet so that Kerry can monitor the fuel pressure, which is critical to correctly tuning the four-barrel carb

The engine bay is pristine and looks original, but it does hide some modernisation and performance enhancements

TECHNICAL DATA MAZDA RX-2 RE COUPE (STANDARD RX-2)

Manufactured JapanAssembled Various countriesProduction 1972–1978Engine Mazda rotaryCapacity 1148ccCylinders Two rotorsComp. ratio 9.4:1Fuel system Four-barrel NikkiMax. power 97kW at 7000rpmMax. torque 156Nm at 4000rpmTransmission Four-speed manualSuspension, F/R McPherson-strut, coil springs / Four-link, coil springsSteering Recirculating-ballBrakes, F/R Disc/Disc

Dimensions

Length 4160mmWidth 1580mmWheelbase 2470mmKerb weight 1010kg

Performance

Max. speed 182kphAcceleration 0-62mph (0-100kph) 9.4 secondsStanding quarter-mile 16.7 seconds

From an era when the rotary engine was full of promise, the Mazda design team came up with an appropriate design

Debate surrounds which vehicle manufacturer was first to develop a Wankel engine–powered car.

Rotary engine returns: 2023 Mazda MX-30 R-EV range-extender hybrid.

Below: Fifty years ago, Mazda created this simple, very pretty, and lightweight coupé. The underside mirrors the owner’s same attention, care, and detail of the topside.

The rotary motor to date has been one of those engineering feats that has almost always delivered more promise than anything else