Despite having been with us for nearly a quarter of a century, the rotary engine is still considered by laymen to be a new idea, not be trusted until thoroughly proved in use. Many motoring buffs, on the other hand, dismiss the rotary as another of those blind alleys which litter the history of the motor car
The idea, which tire came to the public attention in the mid-sixties with the introduction of the rear-engined, single-rotor, air-cooled NSU Spyder, had been developed as far as a running prototype by the mid-fifties when NSU embarked on the, development programme of Herr Felix Wankel’s brainchild. However, early in the sixties, the rotary concept had captured the imagination of Kenichi Yamamoto in Japan and his company, Toyo Kogyo Limited of Hiroshima, entered into a licence agreement with NSU to develop the concept as well. By 1999, Wankel engined Spvders were popular in German motorsport, and Panowitz and Stunz won the GT Rally Championship that year with such a car.
Tooo Kogyo’s development programme had seen the construction and testing of single, twin and four rotor engines and in 1967 came the introduction of the first Mazda rotary engined car, the Cosmos Sports, or 110S, which had a twin rotor, air-cooled engine at the rear.
It looked as tithe rotary engine was to be the thing of the future when NSU introduced the Ro80 at the 1967 Frankfurt Show. With its twin-rotor, water-cooled engine up at the front, driving the front wheels through a torque converter, servo-operated clutch and a fully synchronised gearbox, the Ro80 won instant acclaim as “Car of the Year”.
In 1969, NSU merged with Audi, and only the Ro80 continued to bear the NSU name, but sealing problems gave these fine handling cars a poor reliability reputation and they were withdrawn from the market in the early seventies. Meanwhile, Mercedes-Benz had toyed with the rotary concept with the mouth-watering C-111 sports coupe prototype which had a triple rotor engine developing nearly 300 b.h.p. in its first guise, followed by a four rotor unit producing some 350 b.h.p., but it was not developed further.
By 1973, only Toyo Kogvo were building rotary engined cars – in no less than five models. 1970 had seen the Mazda R-100 through the necessary exhaust emission tests in the USA after considerable research with thermal reactors to clean the exhaust, and export from Japan to the States began. But these early rotary engines were not without problems and these led Toyo Kogyo into financial difficulties, only to be rescued by Japanese banking interests. Nothing daunted, they persevered with the rotary concept through the seventies, introducing the rotary engine to commercial vehicle applications for a brief spell and finally introducing the RX7 to the world in 1978. It immediately took North America by storm and was soon selling 5,000 a month, beating both Porsche 924 and Datsun 280ZX by a handsome margin.
September 1979 saw its introduction in the UK, and demand was soon outstripping supply, even though its reception here was rather critical in some respects. In the middle of last year a revised version, more powerful with improved braking, tyres and revamped interior went on sale and Motor Sport took advantage of an offer from Mazda Car Imports (GB) Ltd to try one of these rotary engined cars over a six month period.
The sleek body of thise 2 + 2 coupe is rather un-Japanese in appearance and has a remarkable first-glance similarity to the 924 Porsche. The Mk. I Mazda came without any spoilers or rubbing strips, and although it looked very useful, there was something rather unfinished about the treatment of the rear of the car. The Mk. II has put all that right. At the front there is a substantial bumper with a plastic air dent below while at the rear is a flexible spoiler wrapping round the sides of the car. The bumper line is continued around the car in the form of rubbing strips linking the wheel arches, and the whole effect is that much more purposeful and finished.
The rear window doubles as the rear hatch and can be opened either from inside, using an electronically controlled release, or with the key from outside. It covers the somewhat small luggage area behind the diminutive rear seats tor seats for diminutive people and supports its own wiper and washer. It opens on gas filled struts. There are thick pillars behind the doors which form part of a strong anti-roll-over frame and which can obscure rearward vision when manoeuvring and, more seriously, when negotiating certain slip road junctions. With the sloping screen and large rear window, the length of the roof is necessarily short, making a sliding sun-roof impossible; instead, Mazda have provided a tilting panel to improve summertime ventilation which can be lifted out completely and stored in a plastic bag behind the rear seats, always providing the space is not full of luggage. The bonnet hinges at the front and is released by a substantial pull catch which often required a fumble amongst the fuse boxes and wiring above the driver’s right leg before it came to hand. A bent wire prop is used for support.
The interior truce of this grey car was deep red, the seat facings being of broad patterned cloth. Plain cloth covered the doors down to knee level, below which the car is covered in thick, almost fluffy, red carpet. The dash is of a colour-matched plastic moulding which rises in front of the driver to shield the black instrument panel which contains three circular dials – a tachometer in the centre, speedometer to the right and dial on the left containing fuel level, oil pressure and coolant temperature gauges. A new of warning lights extends across the bottom of the panel.
Switchgear is nicely designed, but rather scattered – to the right of the steering column are dash-mounted rocker switches for the fuel filler release (also openable by key from outside), for the aforementioned glass hatch, and for the adjustment of the driver’s door mirror (this a four way rocker switch which is about the neatest mirror adjusting switch we have come across). To the left of the wheel is a choke pull and panel light rheostat. On the centre console, below the radio, ashtray and so on but in front of the gear lever, are switches for the rear screen heater and for raising and washing the headlamps. Behind the gear lever, over the transmission tunnel, are switches for the electric windows, electric aerial and rear window wash/wipe. The indicators are controlled with the right-hand stalk, which also rotates to control the lighting, while the wipers and windscreen washer stalk is on the left. The hazard warning light and the high intensity rear-fog lamp switches are on top of the steering column cover and are operated by putting the arm through the upper section of the steering wheel. We found it all too easy get confused by the controls for the minor functions, and to the last day with the car, this driver was opening windows instead of wiping the rear screen.
The heating and ventilating controls on the top of the busy centre console are simple – one lever for temperature and another for mode of distribution, together with a four position rotating switch to control the three-speed fan. We found that the system worked well. In the late summer, the interior kept pleasantly cool without any need to open windows or the roof, while the heater coped with winter conditions quite happily, although in the very worst of the December weather it sometimes proved necessary to sacrifice warm feet for a clear screen.
Below the heating controls is a high quality stereo cassette player, separate from the equally high quality radio. The centre console also houses an ashtray and cigarette lighter as well as clock, low down alongside the rear window heater and headlamp wash switches.
Front suspension in of the MacPherson strut type while that at the back is by coil springs, the live rear axle being located by four trailing arms and a Watts linkage. Gas filled dampers accused and anti-roll bars are fitted at both ends. Steering is by a variable ratio recirculating ball and nut system and is not power assisted. There are nearly four turns from lock to lock, but the variable ratio aspect of the steering means that in normal use the steering feels comfortably high geared, and yet not too difficult to manoeuvre. Iris only when pressing on hard, when significant changes to front wheel direction have to be made quickly, that the low gearing makes itself felt.
The wheels are attractive, broad spoked alloy 5½J x 13 units, shod with 185 / 70 HR Dunlop tyres specially developed for the car by Dunlop in Japan. Sadly, the attractive wheels lost their sparkle as soon as winter conditions and the salty roads had to be negotiated. Disc brakes are fitted all round, and these are servo assisted.
The latest form of Mazda’s twin-rotor, water-cooled rotary engine produces 115 b.h.p. at 6,000 r.p.m. from its two 573 c.c displacement rotors, which give a nominal capacity of 2,296 cc since the rotary engine is effectively a two-stroke. The compression ratio is 9.4 to 1 and the car thrives on 2-star petrol. Since the maximum torque is developed at relatively high engine speeds (of the order of 110 lb. ft. at 4.000 r.p.m. and the torque curve is rather peaky, it is understandable that the RX-7 is low geared relative to its piston-engined brethren having a final drive ratio of 3.909:1.
The apparent low gearing is not noticeable, however, since the turbine-like smoothness of the engine gives a very false impression of the speed at which it is rotating – it is very easy to cruise for miles in fourth at high speeds without realising that you haven’t made the final up-change, and often only reference to the rev-counter will make the driver believe a higher gear may be used. So freely does the engine rev that in the interests of engine life, Mazda have equipped the RX7 with a siren which sounds as soon as 7,000 rpm, comes up.
Starting the Mazda RX7 from cold is rather a different experience from anything else – at first it seems that the choke will not stay out, but as soon as the ignition is turned on an electro magnet holds the control in place and the engine will fire immediately. If the choke control is forgotten, the electro magnet is automatically switched off as soon as the engine reaches operating temperature. The RX7 is fuss-free on a cold engine, provided it is driven gently for the first few miles.
Acceleration from rest is spoilt somewhat by a rather baulky first to second change, and the best we could manage with our rather crude timing arrangements was a 0 to 60 figure in 9.5 seconds, rather slower than the 8.6 seconds claimed for the Mk. 1. Top speed was certainly in excess of 120 m.p.h.
As described in the November 1981 issue the RX7 is easy to live with, especially if most driving is on the open road. City dwellers who do not go far afield might find the car rather tiring, since, in traffic, much use of the gearbox is required to keep the engine running at optimum speeds. The ride is somewhat harsh, but the handling is excellent and the RX7 can be chucked about on country roads in a delightful fashion, the Japanese Dunlops suiting the car admirably.
High speed cruising is relaxing, and after initial annoyance, familiarity soon obliterates the ever present aircraft-like hum as one hurtles along dual carriageways. The brakes are excellent, but need treating with care since excessive pressure will make the Dunlops lock up on a dry surface, and correspondingly more readily in the wet.
The sort of details which go unnoticed in the usual 1,000 mile test make themselves very apparent over a 12,000 mile period, and items which at first sight are functional and praiseworthy become aggravating while others, which might be considered gimmicky initially, become valued adjuncts to motoring. In the former category are the windscreen washers. First, the jet is directed too high up the screen, even when cruising fast, leaving the lower are un-wetted, and therefore smeared: this driver is short, and found this particularly aggravating. Also, the washer bottle is of very small capacity, and on the heavy salted Christmas roads in and around London a washer bottle full would be consumed more quickly than a tank full of petrol. The reservoir for the headlamp washers, on the other hand, seems to be of a much larger capacity, but as it is hidden low down behind the front bumper where it is difficult to fill, and impossible to see, the water could have been splashing all over the place and not going into the reservoir. Sensibly, Mazda have provided a warning light to indicate when this reservoir is in need of replenishment. No such warning exists for the screen washer, but Mazda do recommend checking the oil at each fuel stop, when it is easy to see how much cleaning water remains.
In the latter category, much to this tester’s surprise, are the audible warning devices fitted to the RX7 – not the kind which warns other motorists of your presence, but the siren which operates when the engine is being over-revved and the chimes which come on if a door is opened when the engine is off and the lights are on. Familiarity with a car breeds slack habits and using the RX7 for everyday motoring, not racing round the country roads for fun, but usually in a hurry, it would have been very easy to over-rev that rotary engine without noticing had it not been for the siren, and living in a street lit area, it is amazing how easy it is to leave lamps lit when parking at night.
The owner of an RX7 might be tempted not to obey Mazda’s recommendation to check the oil at each fuel stop, but he would be unwise to do so, for the rotary engine is designed to use oil. We found that oil consumption over our six month period worked out at between 400 and 500 miles per pint. depending on who was driving and in what conditions – consumption went up markedly over periods of short-haul journeys, was in the middle of the range of being used for long distance, high speed work and was least, as one would expect, for gentler long-distance cross country use. Fuel consumption varied from 18.2 m.p.g.. driven extremely hard, to 27.2 m.p.g. to mild touring. The overall average figure for our 12.320 miles with the car worked out at 23.4 m.p.g.
During its spell with us. the car never let anyone down but was not exactly trouble free – just before It was due for its 6.000 mile service, it developed a rather inconvenient flat spot between 4.000 and 5,000 r.p,m. and began to pop and bang on the overrun. This fault was cured at the service, but reappeared towards the end of our time with the car, by which time it was due for another spot of routine maintenance. The finish of the car was excellent in all respects, but certain items of trim managed to come adrift – the panel around the luggage area moving up into the wide pillar behind the passenger seat rattled intermittently and was obviously loose alter 6,000 miles, while the moulded panel covering the windscreen pillar on the driver’s side came completely adrift at 9,500 miles, but remained in place after careful replacement. At 10,000 miles, the interior mirror complete with interior light simply fell off its mounts when being adjusted, and remained loose, despite replacement, for the remainder of our test. Minor problems, perhaps, but the Japanese do have a reputation for perfection…
Improvements which Mazda should consider are the provision of an oil level gauge to save dirtying the hands unnecessarily when re-fuelling and a larger capacity fuel tank – the nominal 12 gallon fuel tank provides a comfortable range of only some 250 miles. With a car so comfortable for long distance driving, a range of 400 miles is a desirable feature. Passenger comfort would be improved if the rear suspension was not quite so hard, and a new compromise between handling and ride comfort might make the RX7 more attractive to a wider sector of the market.
Priced at £9,200, at the time of writing, the RX7 costs more than the basic 924 Porsche (£9,100) and Datsun 280 ZX (£9,143), but offers the equipment of the more expensive versions of these cars. Another obvious competitor in this coupe market is the excellent 2.8 injection Ford Capri – it may not have electric windows, but it does have useable rear seats, better performance and costs £1,000 less. – P.H.J.W.
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The Editor comments
Having experienced rotary engine motoring in the little NSU Wankel Spyder in 1965 and with the very well measured Ro80 in 1969, it was very interesting to make a more prolonged study of the latest version of the Mazda RX7 last year, having tested an earlier version in 1980. The idea was to let various members of the Standard House staff try it, and as I rather lost touch with it during the latter part of 1981, I have entrusted the full report to P.H.J.W. The RX7 with Mr. Yamamoto’s courageous twin-rotor development of the Wankel-motor that NSU dropped and Mercedes-Benz abandoned, is most enjoyable, especially when clear of the traffic, although on motorways the aircraft-like background whine can be sleep-inducing. The gearbox needs to be used a lot in town driving.
Good handling, a nice five-speed gear change, fairly comfortable front seats and a handsome appearance make this an excellent fun car, in addition to which I found the RX7 a very handy, pleasant car for long journeys but with rather too hard rear springs. Essentially a two-seater, we did once get tour adults into it, but only by having one pair of female legs protruding from the back close to the stubby gear lever. The switch gear is high class but scattered, the driver-release of the glass boot lid and fuel filler flap were much appreciated, less so the ding-dong warning of lamps left alight when the door was opened. Disc brakes all round, a rear spoiler, pop-up head lamps, clear and comprehensive instruments, an openable or removable roof and a low built rear are all nicely in keeping with this highly individualist 125 m.p.h. sports Mazda – W.B.