The following is a letter written by Lord Kings Norton to Air Commodore HM Pearson in 1975 and reproduced with his permission.
Sir, In the summer of 1913, when I was just 16 years old, I managed…
LONG gone are the days when Japanese cars had a stranglehold on just the lower end of the market. As they have had to face ever stiff opposition from developing motor industries from the non-industrialised parts of the world together with the barrier of import quotas, there has been a perceptible move towards the luxury and specialist car segment where profit margins are considerably more worthwhile.
While the Eighties was the decade which saw the Japanese automotive industry usurp the Europeans in terms of pushing technological boundaries, it has been Mazda alone which has continued to plough its lonely trough with the rotary engine. If there was a time when that concept was going to be dumped by the manufacturer, it would have been in the mid-Seventies at the time of the fuel crisis, since this design of engine has never shown much sympathy for conserving ‘fuel fossils’, but Mazda endured with the concept.
The original RX7 was a pretty little coupe which inevitably enhanced the sales appeal. Unlike most Japanese models, the shape was retained for eight years, almost double the length of time usually allowed, which helped give the car an established identity. A new shape was inevitable, however, but by the time of its launch in September 1985, reaching Britain in 1986, in was in danger of being outclassed by its many rivals. A performance that was creditable
in the late Seventies was looking a little wan by the mid Eighties, especially when matched against some of the models with which Mazda wanted it compared. It was in serious danger of being relegated to the ranks of the also-rans despite the installation of the new twin rotor engine.
Now, however, Mazda has redressed the balance. Announced in the summer of 1989, and released on sale in Britain in the early autumn, the RX7 has not only been turned into a convertible, but both it and the coupe have been blessed with a twin turbocharged engine. Both models are now endowed with a performance that goes with the looks. With a top speed of over 140 mph and a to 60 mph in under 7 seconds, the Mazda is very definitely in the supercar league. The unit itself is still the twin rotor Wankel engine with three 654cc combustion chambers per rotor and is judged to equal a swept volume equivalent to 2.3 litres. The compression ratio has been raised to 9.0:1 while microprocessorcontrolled electronic fuel injection allied to the ‘twin scroll’ Hitachi turbocharger, the computerised control of the wastegate valve and the lightweight rotors boost power to 200 bhp at a dramatically high 6500 rpm. Maximum torque is 195.2 lb. ft at 3500 rpm but fortunately the engine is
endowed with plenty of punch from a usefully low 2000 rpm.
The beauty of this unit is less the high power output than the way it is able to deliver it. The fact that a computer chip is placed between the accelerator pedal and the engine ensures instant response, no matter the speed, and because the torque curve is virtually smooth between 2000 and 5000 rpm, the pick-up is always immediate. The absence of turbo lag is attributed to experience learnt from the race track.
The turbocharger itself is an interesting piece of machinery. As bolting an ancillary turbocharger onto the rotary engine is not the most efficient way of extracting futher power, Mazda have developed a ‘twin scroll’ piece of equipment. Similar in principle to the variable pitch propellor, the turbocharger has two separate chambers, each of which reacts to the speed of the engine. Below 2500 rpm the gases are directed to the part of the blade which is able to react more quickly to low pressure, while above that engine speed, a valve opens which directs the gases into the second chamber onto blades which can withstand a greater pressure of air. This more efficient use of blown gases ensures not only greater power but also decreased turbo lag.
The most noticeable aspect of driving a rotary powered car, especially when driving such a machine for the first time, is the smoothness of the engine. There is simply nothing to compare to it. Even the noise is different, the strange whine which emanates from beneath the sloping bonnet when under hard acceleration denoting that there is something unconventional lurking there. The only other mechanical noise is the whistle from the turbo which can be heard on rare occasions, otherwise the boost gauge the only clue to this being a turbocharged car.
As with most Japanese cars, changing gear is delightful, only a short movement of the pleasant-to-use, stubby gear lever required. As mentioned the flattish torque figures negates the necessity to keep changing gear, but such is the smoothness of the engine, such is the urge with which it is communicating to the driver that it wants to get a move on, and such is the ease of changing gear, that the driver is seduced into using the gearbox more than is really necessary. If one ignored the siren-like call to change gear and kept it in fourth, for example, the 40 to 60 mph and 50 to 70 mph can be reached in under five seconds and 60 to 80 mph in 5.2 seconds. In fifth the figures are 8.9, 7.5 and 7.9 respectively, good enough to discourage changing gear and generally more relaxing, but that would be to deny oneself the exhilaration of full throttle acceleration in third gear when the car sits down on its haunches and propels itself like a bullet from a gun. However there is one almost ruinous consequence — the fuel consumption can be horrendously high. Mazda do claim that over 30 mpg is attainable — it may be but at the expense of being driven about as if by the district nurse. 14/15 mpg is not an unusual con
sumption when being driven vigorously, and anything over 20 mpg must be considered as a bonus.
Where the coupe has been criticised for having rock hard suspension, the cabrio’s is softer. Combined with comparatively narrow section 205/60/15 Bridgestone RE71s and alloy wheels the ride is better. The handling, however, is not all that it might be despite the use of Mazda’s socalled Dynamic Tracking Suspension System which dictates toe control when cornering and braking. The body, which at 1420 kg is 60 kg heavier than the coupe thanks to the steel reinforcement at strategic points, has a
tendency to roll just a little bit too much for comfort at the limit. Encouragingly, though, body rattles were at a minimum and scuttle shake insignificant, although this is an area where no two cars are alike.
Traction, even in the wet, was superb, the car always capable of putting its power down through those relatively narrow tyres, never scabbling for grip. It is at its best along sweeping country roads where the line can be held on the throttle rather than resorting to a flurry of arms twirling the power assisted steering wheel. The steering was an area of criticism on the original Mark 2 coupes for being too light and sensitive, but that on the test cabrio was fine, the car going exactly where it was told to. With 2.7 turns from lock-to-lock and capable of a turning circle of 32 feet, the steering lock was particularly good, a useful factor when taking into consideration urban driving and parking.
What is particularly disappointing in this car was the lack of an anti-lock braking system which should be considered essential equipment in any car capable of nearly 150 mph. As it turned out, the ventilated discs, 10.8 in at the front and 10.7 in at the rear, were powerful and effective while the absence of an ABS system did not deny the driver that certain ‘feel’ for the car.
The hood with its heated glass rear window is activated by an electric switch, but the dictates of American legislation demand that the car is in neutral with the ignition and handbrake on before it will work. A targa-type roof panel can be removed while the rear of the hood is kept erect, or the whole lot can be lowered and the hood stowed away under a neat hood bag, but it is a fiddly job. At the expense of rear seating, a wing deflector is located behind the front seats, its function to prevent too
much exposure to the elements for those who do not have the wholeheated commitment to open air motoring. This car does not even pretend to be a 2 + 2, but at least in that respect it is more honest than some others.
Front seat accommodation is supportive, the leather upholstery adding to the overall appeal of the car. The legroom is good, the pedals well spaced and the leather covered steering wheel feeling good in the hand. Although the car lacks height adjustment for the seat it can be found on the steering column. Nice touches include buttons in the interior for the boot and filler flaps and the illuminated ignition and door switches. It is ergonomically sound and the dials are all analogue and the orange-on-black
dials generally easy to read. The car is well equipped with central locking, cruise control, electric windows and mirrors complementing the hood mechanism. Criticism, though, must be made of the poor spread of light on dipped headlights, especially on such a high-speed car, and the lack of storage space inside, an element compounded by the high sill to the relatively small boot. Altogether this is a very creditable alternative to some of the European supercars on offer. Wearing a price tag of £23,999 it is many thousands of pounds cheaper than cars with more pedigree but less performance. The rotary engine, now that it has been so successfully turbocharged, propels the car along smoothly and vivaciously. Driver comfort is good and the
option of open air motoring is something that only a few other cars can offer. The RX7 Turbo Cabrio seems to have everything in its favour, but there is still a question mark hanging over it. Its high consumption of fuel somewhat negates its relatively low purchase price, and it will certainly make serious dents in owners’ wallets. As a second car after the kids have left home, however, or for those who have not yet got themselves lumbered with a mortgage, it has to come under serious consideration. mpg: 16.5
Model: RX7 Turbo Cabriolet. Importer: Mazda Cars (UK) Ltd. Mount Ephraim, Tunbridge Wells, Kent TN4 8BS.
Type: 2-seat sports convertible. Body Weight: 1420 kgs.
Engine: Front-mounted, twin rotary, 654cc x 2, 9.0:1cr, turbocharger, electronic fuel injection/ignition. Power: 200 bhp at 6500 rpm. Torque: 195.2 lb ft at 3500 rpm. Transmission: Rear-wheel drive, 5-speed manual gearbox, single dryplate clutch.
Suspension: (Front): MacPherson strut, alloy lower arm, anti-roll bar. (Rear): Multi-link semi-trailing arm, coil springs, anti-roll bar.
Steering: Rack and pinion, electronic speed-sensitive power assistance, 2.7 turns lock to lock. Turning circle: 32 ft. Brakes: (Front): Ventilated discs, 10.8in dia, 4-pot caliper. (Rear): Ventilated discs, 10.7in dia, 2-pot caliper. Wheels and tyres: 205/60 ZR15 tyres on 6.5JJ x 15 alloy rims. Performance: Max Speed: 145.4 mph; 0-60 mph: 6.7 secs.; 40-60 mph (in fourth gear): 4.7 secs.; 50-70 mph (in fourth gear): 4.7 secs.; 60-80 mph in fourth gear): 5.1 secs. Consumption: mbn Inc A Overalltest119U1eS,
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