The Mazda RX-7
The very pretty, rotary-engined Mazda RX-7 has taken the North American sports car market by storm since it was launched there in May 1978, two months after its introduction in Japan. June-July 1979 sales figures of 5,000 per month in the USA easily exceeded those for the Datsun 280ZX and Porsche 924, the popular peers in this intensively competitive and critical market. Today, September 1st, the RX-7 goes on sale in the UK and Motor Sport is pleased to publish this exclusive road test of the interesting newcomer.
At the time of the test, our silver RX-7 was the only example registered in the UK for road use, but to British race-goers this sporting Mazda model was already a familiar sight, the rapid Pentax-sponsored car of Tom Walkinshaw then leading the British Saloon Car Championship. Saloon Car Championship? There’s the irony, for though this petite 2 plus 2 undoubtedly looks like, has the character of, and is described by Mazda as a sports car, its internal dimensions comply with FIA saloon car regulations, the proverbial quart in a pint pot, much to the chagrin of Walkinshaw's opposition. In the USA the sports car definition is more clear cut, versions for that market having only two seats within the same 95.3” wheelbase as the 2 plus 2 sold in Europe and Japan.
The styling of the road test car reminded most professional observers of the old Lotus Elan Plus 2, perhaps Colin Chapman’s most elegant design. Could it be that D. S. J. inspired Toyo Kogyo, the Hiroshima-based manufacturers of Mazdas, when he described his road test Mazda 110S, the RX-7’s direct ancestor in Mazda sports car terms, was the World’s first rotary engined production car; since they launched it into full production in 1967 the Hiroshima factory has produced well over 1 million rotary-engined cars.
Public tastes have changed since 1968 and to meet them this latest Mazda sports car is much more civilised and sophisticated than the 110S, a noisy, oversteering and very controllable machine which D. S. J. found great fun. The RX-7 doesn’t have that same degree of in-built fun factor, but all production sports cars have had to go this way to suit public demands. Instead it has adhesion, comfort, quietness and all the “mod-cons” to make it civilised everyday transport for the discerning motorist of the ‘80s, a softer breed than he of the ‘60s. But the RX-7 still has enough of that fun factor to make it highly enjoyable.
Its layout is conventional – front-engined, rear wheel drive. Viewed in silhouette the delicately curved lines look aerodynamic and bear this out with a respectable drag coefficient of 0.36. D. S. J. described the 110S as “frilly on the outside”; the RX-7’s very balanced looking shape is free from extraneous protuberances or fussy trim, the “cleanest” car to come out of Japan. The colour-matched front bumper is integrated with the body instead of sticking out like a sore thumb, yet still meets American impact regulations. Halogen headlights are retractable, radiator ducting tucked away between the bumper and a shallow and vulnerable bib-type spoiler. The curve of the low bonnet line flows into a curved and steeply raked, laminated windscreen, bonded in place, the smooth theme continuing over a short roof section into a wrap-around rear glass area. From a distance, this vast expanse looks to be all one piece, but is in three sections, the curved quarter panels fixed, the big, frameless centre panel forming an opening hatchback supported on twin hydraulic struts. It can be released either electrically by a push-button on the facia or by a conventional lock on the tail panel. Overall height is a modest 49.6 in. The bodywork is sheet steel, produced with great concern for anti-corrosion; treatment of specific areas varies with the particular rust threat, some being galvannealed, others electro-galvanised, yet others PVC coated, while sections in close proximity are separated by plastic protectors.
The compact, Wankel-type rotary engine allowed a low bonnet line without headaches for Mazda’s engineers, who describe its installation as “front mid-engine”, for the unit sits well back behind the axle centre-line, to permit a 51/49 weight distribution. This choice of a twin-rotor engine is interesting, probably controversial and a monument to one man’s faith and perseverance. Kenichi Yamamoto, Managing Director and General Manager of Research and Development at Toyo Kogyo, and the acknowledged world expert on rotary engines (he has worked on them since Mazda made a licence agreement with Audi NSU/Wankel in 1961), fought hard and long for the survival of the power unit which all but finished his company during the ’73-’74 energy crisis. The US market’s reaction to the poor fuel consumption of the rotary of the day almost pulled the mat from under Toyo Kogyo. Yamamoto worked on stolidly, achieved a claimed 40% improvement in fuel economy and now, in the midst of another energy crisis, has the Americans scrabbling to buy his latest rotary offering.
The quest for economy and improved emissions had not had an adverse effect on power output. In fact with 105 b.h.p. DIN at 6,000 r.p.m. and 14.7 m.k.g. torque at 4,000 r.p.m., this 573 c.c. x 2 displacement twin rotor unit, which is rated at 2,292 c.c. by FISA’s multiplication formula for motoring sport, is about 6% up on the same displacement 12A engine in the familiar RX-3. Nonetheless the figures sound modest, yet a combination of slippery shape, sensible gearing and a weight of 20.5 cwt. enabled the test car to pull a maximum of 121 m.p.h. and accelerate to 60 m.p.h. in around 9 seconds. Mazda horses must be pretty strong ones, for the RX-7 is substantially quicker than the slightly lighter TR7, of identical b.h.p. and more torque . . .
Economy, emissions, reliability and serviceability are all said to be improved in this latest Mazda 12A rotary. Changes to the metallurgy and construction of the rotor housings and rotors, repositioning and reshaping of the combustion chambers in the rotors, improvements to the all-important apex and corner seals have been part of the RX-7 engine’s maturing process. It is fitted with a fully transistorised, high energy, contactless ignition; one distributor fed from two coils contains individual systems for the trailing and leading spark plugs in each rotor housing. The plugs are specially developed NGK triple electrode type.
The UK rotary engine carries the same detoxification equipment as the US Federal engine, including a thermal reactor, a secondary air supply into the exhaust port areas from an air pump, deceleration control, crankcase emission control and an electronic control unit. The carburettor is a down-draught, two-stage, four choke Nikki. The engine runs a compression ratio of 9.4:1 and happily consumes two-star fuel. Ease of routine maintenance is a side benefit of the rotary engine design; alternator, distributor, carburettor, air filter and oil filter and filler are all positioned on top of the engine, which internally has very few moving parts. The front-hinged bonnet has to be propped by hand.
Simplicity and ease of service carries through to the suspension. McPherson struts at the front wear coil springs tapered at their lower ends so that the tyre centre can run closer to the king pin axis, to give a smaller king pin offset for better braking stability and to reduce steering vibration. Tie rods give fore and aft location for the bottom arms. An anti-roll bar completes the layout. A live rear axle is located by four trailing links, offset Watt linkage with unequal length arms, an anti-roll bar and vertical, gas-filled shock absorbers mounted behind the axle tubes. Coil springs seat on top of the tubes. On paper the axle looks to be extremely well located, so we were surprised to fine axle tramp during our acceleration tests. This did not obviate itself during normal road driving.
The dual circuit braking system has a 7” direct servo and pressure proportioning bypass valve. Front discs are of 9” diameter and ventilated. Rear drums are mildly finned and measure 9” x 1.3”; they give a very effective handbrake via a lever mounted on the passenger side of the transmission tunnel.
First impressions of all who drove our test RX-were of the ease and pleasantness of control, a complementary combination of light and smooth steering, a delightful five-speed gearbox, light, progressive clutch, well-placed controls and above all a feeling of tautness, smoothness and tractability right through the drive line. Characteristics which would smooth the efforts of even the least co-ordinated driver. Much of this has to do with the flat torque curve of the rotary engine, which is turbine smooth all the way from the 1,000 r.p.m. tickover speed to the 7,000 r.p.m. red-line. There is no definite point where the power begins to build up (no camshaft means no “camminess”!), although there is a step in throttle progression when the secondary chokes open. A warning buzzer shrieks as the tachometer needle passes 6,800 r.p.m. which it does all too easily in first and second; although the engine will rev safely above the 7,000 r.p.m. limit, to do so regularly will reduce the life of the seals. We found there to be no advantage in revving beyond the limit during our performance tests. Make no mistake, though, the engine does thrive on revs to release its natural liveliness, but the speed and slickness of the gear change, controlled by a big leather knob, makes this a pleasure rather than a chore. The 3.909:1 final drive is a happy compromise ratio for acceleration and fast cruising, the latter in conjunction with an overdrive fifth gear in which 100 m.p.h. equates to 4,750 r.p.m. I would have preferred a narrower gap between the 52 m.p.h. 2nd gear and the 84 m.p.h. third gear. Although I didn’t try it, fourth speed should pull to 7,000 r.p.m., equal to the 121 m.p.h. maximum in fifth. Maximum speed needs a long, long wind up, but 110 m.p.h. plus is reached easily. The single plate, diaphragm clutch had no problems coping with the harsh standing starts of our performance tests.
Those tests, on a car with only 1,500 miles on the odometer and on a less than ideal surface for tyre bite, showed that those 105 horses are very efficient ones, shires rather than ponies, for the performance figures more or less parallel those for the 3-litre Capri S. They are as follows:
0-30 m.p.h., 3.3 sec. 0-60 m.p.h. 9.2 sec.
0-40 m.p.h. 4.7 sec. 0-70 m.p.h. 12.1 sec.
0-50 m.p.h. 7.0 sec. 0-80 m.p.h. 15.2 sec.
Standing ¼ mile, 17.0 sec.
At the other end of the performance scale the RX-7 is a very flexible town car, happy to pull down to 1,200 r.p.m. in the gears. But considerable exposure to particularly heavy London traffic produced a top-end misfire when the engine was opened up for the first time out of town. This plug fouling did not occur on a US specification are driven in heavier traffic in Los Angeles recently.
Economy, or lack of it, was one of the worst features of the early Wankel engines. Looked at in terms of the performance offered rather than the nominal engine capacity the figures for the RX-7 seem reasonable. Department of Energy figures quote 18.1 m.p.g. for the Urban Cycle, 33.2 m.p.g. at a constant 56 m.p.h. and 27.0 m.p.g. at a constant 27 m.p.h. in mixed use, including commuting into heavy London traffic from Hertfordshire and using more revs most of the time than most owners would, the test car averaged 18.61 m.p.g. on two-star, but this rose to a respectable 25-26 m.p.g. under motorway conditions, a figure paralleled by the American RX-7 I drove down the Pacific Coast Highway from San Francisco to Los Angeles. The fuel gauge on both cars was pessimistic. The tank holds 12.1 gallons and is slow to accept the last couple. Although modifications to the carburettor float chamber are said to have eradicated the old bugbear of fuel cut off during hard cornering, a similar symptom exerted itself during sustained 100 m.p.h. cornering at our test track when the tank was down to its last two or three gallons. This would seem to indicate a problem at the pick-up in the tank, but we were never troubled by it on the road.
Oil consumption must also be taken into consideration in the case of a rotary engine, which has a total loss system, since it uses oil to lubricate the gas seals by metering oil into the combustion chambers. The test car used approximately ¾-litre per 600 miles.
No starting problems were encountered with the engine hot or cold. The pull-out manual choke on the left of the steering column is locked in position elector-magnetically when the ignition is on. It is automatically released when the engine is warm should the driver forget to push it in earlier. Start-up is always accompanied by a paraffin-like smell from the exhaust, which emits almost a V8 burble when the choke is out.
With a wide track (4’ 8”) and low centre of gravity, the 14’ long RX-7 looks as though it ought to handle well and doesn’t disappoint. When the test car arrived it wore Bridgestone tyres, original equipment in Japan. So equipped the car was a little disappointing on “turn in” into corners and on the degree of understeer. Subsequent tyre testing found it to be much more responsive and better balanced on Pirelli CN36s and these have now been adopted as standard equipment for the UK market. They are of 185/70HR 13” size mounted on 5½J alloy wheels. The handling is of a very safe and progressive nature, with a mild degree of built-in understeer to safeguard the less competent. Pushed hard it makes a gentle transition to mild oversteer. I was inclined to think that the Porsche 924 had better handling than the RX-7, though it is rougher and noisier in other respects, until I tried the RX-7 over the same section of “mini-Nürburgring” test track that I took the road test 924 in 1977. Where the 924 had felt “tip-toey” and changed very abruptly to roll oversteer, the RX-7 was safe and progressive.
Whatever its other shortcomings a live rear axle, with zero camber change, can be an asset to predictability and the RX-7, which responds well to quick changes of direction between opposing corners, bears this out. Traction too is excellent.
Bumps in mid-corner are a reminder of that rear end rigidity, but not unduly perturbing and the general stability on the long, 90-100 m.p.h. corners on the test track was impressive. Roll angles are modest. Hard cornering causes the windscreen washers to trickle incontinently, just like those of the Mazda Hatchback I had on long term test last year.
So the RX-7 handles well, with no vices. But somewhere its solid handling, taut though it is, could do with a bit more liveliness; a keen driver would get more satisfaction out of the more “chuckable” handling of Ford’s RS 2000, for instance. Part of the reason is compromise to achieve a good ride without making the suspension too stiff – though Lotus’ successful recipe has always been to combine relatively soft springing with good damper control. However, more fundamental to overall feel is Mazda’s insistence on variable ratio recirculating ball and nut steering. It lacks the direct communication and precision of good rack and pinion and has too much lost motion. On the credit side it does cut down bump reaction, is light and smooth enough and doesn’t require overmuch twirling; the 3.7 turns lock to lock are more an indication of the good turning circle than low gearing. It is controlled by a very comfortable, leather trimmed, thick rimmed wheel of quite small size and with the horn push mounted where all cars ought to have it – in the central boss.
By sports car standards this Mazda’s ride is very good, live axle or not and the suspension works away quietly, without undue thumping. UK owners will notice a bit more tyre thump from the Pirellis than overseas owners will from their Bridgestones, but the handling benefits are worth it. The ride characteristics are matched for driver and front passenger by superbly comfortable, cloth trimmed, reclining bucket seats with built in head restraints and contoured hip supports. They are built up with urethane inserts with three different levels of hardness: in the centre sections, for lateral support and for lumbar support. After spending nearly fourteen hours in one day in the seats of that American RX-7 without suffering any aches and pains I feel well qualified to judge their comfort level!
The disc/drum brakes are light in action, but not over sensitive. They are little bit lacking in feel. Actual stopping power is good and they impressed by the way they stood up to the rigours of our test track without fading.
Noise levels are very civilised, a factor which combines with sheer ease of driving and general comfort to make this sporting Mazda a very relaxing car to drive by any standards. From a gentle burble at tickover the engine note rises to a busy drone towards the upper end of the scale, but never becomes over-obtrusive. On a light throttle at medium speeds there is barely evidence that the turbine-like rotary engine is functioning at all. I have spoken above of the low levels of suspension noise and the wind noise is of modest proportions. All these characteristics, the inherent straight line stability and the general lack of vibration and harshness give the little RX-7 a comfortable high speed, long distance cruising ability which its size belies.
The thought which has gone into body design and chassis behaviour continues through to the attendant interior trappings, which include as standard a separate Clarion AM/FM stereo radio and a cassette player with four speakers. An electric aerial, with manual switch, is part of the package. Tapes can be accommodated in a lidded locker between the seats. Japanese plastic interiors have a reputation for lack of taste, but the RX-7's facia is conservative and neatly laid out. Three large instruments are gathered in a cowled nacelle and as befits the free-revving Wankel engine, central pride of place is given to the 8,000 r.p.m. tachometer, itself a model of Japanese electronic ingenuity, for it doubles as a voltmeter when the ignition is turned on, before the engine is started. On the right is a 130 m.p.h. speedometer with trip and on the left a combination dial incorporating a clock, water temperature gauge and that pessimistic fuel gauge. A row of warning lights along the base of the nacelle includes two for low oil and low water levels. The right hand steering column stalk and the big knob on its end look after two-speed plus intermittent wipers, powerful washers, headlamp, flash, dip switch and winkers. The lamps master switch is on the left. The headlamp pods rise quickly, driven by twin electric motors, when the headlights are switched on. A separate switch on the centre console enables the pods to be raised without the headlights on, useful for car washing and so on. Alas there are no separate daylight flasher lamps and the headlights do not rise automatically with the flasher switch. The handbook advises that the pods be raised and left up with the separate switch if flashing is to be required, but who wants to run around with the pods raised in daylight, with their 6% increase in drag, on the off-chance that headlight flashing might be needed?
A neat centre console houses the two sliding quadrant heater/ventilation controls and knob for the multi-speed heater fan (the engine cooling fan has a viscous coupling, by the way). A good supply of fresh air can be supplied through twin central vents, and vents at the ends of the facia and others in the footwell. Warm weather in Britain and scorching Californian heat made heater trials impossible, but our photographer commented that the V-registered photographic car (our test car was T-registered) was slow to demist when he was caught in heavy rain. There are separate demister vents for the side windows and the opening section of the rear glass is heated. The radio and tape player are next in line down the console and switches for aerial, rear screen, headlamps pods and cigar lighter below these. The console continues rearwards around the gaitered gearlever and has a useful coin tray in its rear. A sliding-top ashtray between the seats is pinpointed by a green light at night. The glove box is lockable.
The driving position is well nigh ideal for all but very tall people, who may find the RX-7 a little cramped in any case, and the general ergonomics of a high standard. That nifty gearlever lies close to hand, the pedals are sensibly placed and the left foot has its own adjustable rest. All round visibility is first class. Seat belts recoil into the side pillars (part of a roll-over hoop) and are comfortable to wear.
Adults would not wish to travel very far in those rear seats, for both head and leg room are understandably restricted, but for occasional adult use they are a very useful asset. As children’s seats they would seem to be comfortable and cosy. Access is gained by tipping the front seat back rests, which annoyingly don’t return to their original position. The front passenger seat slides forward when the back rest is tipped and again needs readjusting afterwards. Luggage space is restricted, though not impractical when the rear seat back rest is in place. Some sort of cover would be desirable for this luggage area, like the roller blind of the 924. There are straps on the floor for tying down suitcases. The rear seat folds down to form a spacious, flat luggage area. Tools are mounted behind the carpet in the tail panel and the spare wheel lies beneath the boot floor carpet, which had already taken on the shape of the wheel and tyre in the test car, suggesting a fast wear rate.
At £8,549 this attractive Mazda is aimed at an expensive and demanding market sector where charisma can count almost as much as engineering excellence. Unusually for a Japanese car the RX-7 has the looks which ought to gain it that charisma in the right circles. More than that it is especially easy and pleasant to drive, comfortable and uncannily smooth and vibration free. It is a league away from the old hairy-chested sports car theme, a delightfully civilised and practical sports car which should hold no qualms for the inexperienced and give plenty of pleasure to the experienced. Mazda seem to have conquered all the bugs which gave the Wankel engine a bad name in its early days and made the benefits of turbine smoothness well worth having. Cleverly engineered and well finished the RX-7 is very easy to live with; I enjoyed it immensely. – C. R.