Rotary Survivor

Driven to Write profiles a refugee who made it in the new World.

1978 Mazda Rx-7. (c) flickr

During the early 1970s, it appeared as though Toyo Kogyo’s Mazda division had stolen something of a march on the auto industry. Alongside Germany’s NSU, Mazda invested heavily into wankel engine development and while Neckersulm’s all-in commitment saw them over-reach themselves with 1967’s stellar RO80, Mazda’s more calibrated approach appeared for a time to pay dividends – especially in the United States.

Chief among the advantages of rotary was its low NOx emissions, a matter which perhaps offset its excessive hydrocarbon output. And as US pollution laws began tightening, especially in California, rotary looked like being the industry-wide solution – especially while oil prices remained low.

Unlike their German counterparts (apart from a toe in the water halo-car in the comely form of 1967’s Cosmo), Mazda’s rotary-engined offerings were simply variants of existing saloons, coupés – even pick-ups and estate cars, a matter which no doubt aided Toyo Kogyo’s cause.

The 1973 oil embargo changed many things, not least the industry’s direction of travel. As a panic-stricken auto business took stock of the gaping abyss that had opened at their feet, the industry-wide interest and investment into rotary was hurriedly diverted into lowering fuel consumption via existing technology.

(c) rx7fb.com

The oil shock hit Mazda hard and by mid-decade Toyo Kogyo was staring bankruptcy in the face. Yet despite this, Mazda kept faith, and having convinced backers at Japan’s Sumitomo Bank of the logic in continuing rotary engine development, Mazda’s engineers largely solved the unit’s chronic rotor-sealing issues.

Mazda’s sales recovery came to some extent on the back of the 1977 323 Familia model, which became a Global sales success. This conventionally engineered hatchback line, alongside Mazda’s respected light commercial range not only transformed their fortunes, but would be sufficient for Ford to take the first of several equity stakes in the Toyo Kogyo business in 1979, culminating in a 33% stake by the mid-’90s.

Initiated as project 605 in 1970, but like so many model programmes of the era, delayed by the turmoil of 1973, elements of the 323 platform were believed to have been adopted to form the basis of a compact rotary-engined 2+2. Launched in 1978, the Savanna RX-7 saw Mazda enter a market Nissan was in the process of abandoning as their Z-series sports model became an increasingly bloated and upmarket GT.

Employing the same basic 12A twin-rotor engine as the outgoing RX-2 model, the powerplant was heavily modified to improve gas sealing, wear rates and engine longevity. Mounted in what Mazda described as a ‘front-midships’ position within the wheelbase, the 573cc per rotor cell unit was mated to a unique five-speed manual, or a three speed automatic transmission made by Jatco, a consortium involving Ford, Toyo Kogyo and Nissan.

In launch specification, the RX-7 developed 100 SAE bhp at 6,000 rpm (they were said to be safe up to around 7,000), while peak torque of 105 lb/ft was developed at a heady 4,000 rpm. Top speed was a claimed 125 mph.

Suspension was by MacPherson struts, while a well located live axle was employed at the rear using four radius arms and a lateral Watts link. Anti-roll bars were fitted at both ends, and Kayaba gas-filled dampers were mounted at the rear. Disc brakes were specified all round, and while a rack and pinion system was considered, the steering was by a more Familia’ recirculating ball arrangement with 3.7 turns between locks.

The initial design brief called for ‘functional styling’ and was carried out by Mazda’s own design team in Hiroshima. Clean limbed, sleek and largely uncluttered, the shape (with a cd of 0.36) however risked allegations of blandness. Originally intended to be a one-piece affair, the lifting centre section of the glazed rear canopy was allegedly adopted for cost reasons. At the time, the RX-7’s style was compared unfavourably with the visually similar Porsche 924, but in retrospect it is debatable which of the pair has dated best.

With a low centre of gravity, a high roll axis and a 51/49 per cent front to rear weight distribution, RX-7 dynamics were well regarded, with perhaps a slightly more US-centric balance between comfort and outright handling prowess. But with a lighter front end than its front-engined rivals, excellent stability and fine balance, the Mazda proved a creditable and entertaining proposition.

With almost 475,000 of the first series RX-7 built, it proved a notable success for Mazda, both in commercial terms and in justifying ongoing investment into the rotary powerplant. Combining attractive looks, fine handling, a spacious, well planned cabin and a turbine-smooth, free-revving (if rather thirsty) power unit with the build integrity and considered fitness for purpose of a Japanese automotive product, Mazda’s RX-7 saw the rotary come of age.

(c) autoevolution

Having latterly regained full control from Ford, Mazda, while ploughing its own technically admirable furrow, is believed to have recommitted to the Wankel cause. However, after four generations (if one includes the more recent four-seater RX-8 derivation), the ever-tightening screw of emissions regulation and industry-wide push towards EVs looks increasingly likely to mark the end of the line for the RX-series.

So the rotor turns.

Author: Eóin Doyle

Founding Editor. Content Provider.

3 thoughts on “Rotary Survivor”

  1. In the early Eighties I owned a Lancia beta spider for a very short time. With that car I was following one of those RX7x on a warm dry summer evening down a nearly empty autobahn. When the Mazda driver saw me approaching from behind he gave his car a good prod with his right foot and we were going down the road at serious speed for forty or fifty kilometres.
    It was fascinating to watch the Mazda’s exhaust tailpipes during that drive. The short straight pipes made it possible to watch the baffles in the rear silencer which changed colour depending on engine load. Every time the Mazda accelerated the exhaust turned bright yellow, nearly white. When the driver took his foot off the throttle the pipes immediately turned orange, then bright and then dark red until they didn’t seem to glow anymore only to become yellow again in the next second.
    That was an impressive demonstration of the Wankel’s impossibly bad thermodynamic efficiency.

  2. My good friend and fellow car enthusiast has just sold his Rx8 after a very short ownership,his second one apparently and this was down to abismal fuel economy and fear of engine failure.
    Between us we have experienced ownership of five rotaries without any failures but having moved to electric I won’t be sliding backwards to a rotary and it seems my friend won’t either.
    Must say the Rx8 packaging as a 2+2 sports machine was impressive but is there really a market for this type car with the trend toward taller more human friendly products seen today.

  3. Before anyone gave much thought to it, the lousy combustion chamber shape of the Wankel was overlooked due to the overall smoothness of its operation.

    Whatever demerits the piston engine has, it at least has an almost unchanging shape and volume around top dead centre due to geometry. By luck, not design, since steam was what moved pistons for a century.

    The combustion chamber of a rotary has no piston slowing down, stopping, then reversing at TDC giving that prized semi-static volume in which to explode a mixture of fuel and air. By 15 degrees after TDC you’d better have burned all that mixture in a piston petrol engine or you’ve done something wrong. Diesels can be somewhat different due to the excess air inducted.

    Pity the poor rotary. Its combustion chamber shape and volume is on a rapid change movement at all times. No almost grounded point for setting off the burn. So, you add in more fuel to get enough of a bang for the power you want, which lowers peak temperatures and thus NOx but leaves a lot of unburned fuel – hydrocarbons. Mazda’s solution to that was the thermal reactor, a barrel in which to burn up the excess fuel. Not very efficient. My brother had an RX-3 wagon in the middle 1970s and it certainly got out of its own way and gave a solid 13 mpg when he flogged it.

    Mazda might bang the gong for a rotary revival now and then, and posit range-extender versions running at a single rpm to charge a battery. That way, the disadvantages can be minimized.

    The spark-controlled petrol compression ignition engine SkyActiv X engine due out shortly in the next Mazda3 is probably a breakthrough though. Lateral thinking that none of the HCCI research PhD types had thought of in the last 35 years. They have spent decades trying to get repeatable self ignition points at various rpm and loads. But changeable petrol fuel chemistry variations with every tank-load meant the timing when ignition spontaneously occurred jumped all over the place. Then Mazda announced the obvious last year, and I bet the rest of the researchers probably mentally committed hari-kiri. All I see on various of their websites is a complete lack of acknowledgement of Mazda’s success as if it hadn’t happened. One does have to protect one’s research grants after all.

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