Mazda Cosmo Sport (1967)
Publication: Car Graphic
Format: Road Impressions
Date: August 1967
Author: “C/G Test Group” (uncredited)
An Incredibly Flexible Engine
Testing a revolutionary mechanism like the rotary piston engine for the first time can be a very enjoyable and sometimes unsettling experience. However, after test-driving the Mazda Cosmo Sport for about 600km, we found that it had the expected inherent high-speed capability, but also amazingly tenacious power even at low engine speeds, and was flexible enough to withstand use in crowded cities.
If you were to drive a Cosmo without any prior knowledge, most drivers would probably not realize that this is a car with a completely new type of power unit. However, if you were asked exactly what type of power unit it was, you would probably not be able to answer with confidence, either. Starting is not instantaneous, and it is necessary to turn the starter for quite a long time. At its idle speed of 700rpm, the engine feels and sounds like a two-stroke sports engine, vibrating the entire body of the car quite a bit, and the exhaust sound is powerful, also like a large two-stroke. However, once the engine speed exceeds 1000rpm, the vibrations melt away and the engine response becomes literally as smooth as an electric motor, and it feels like the engine rotation will be limitless, making you aware that there is no valve gear to crash. Even at high engine speeds, mechanical noise does not increase significantly, and the intake and exhaust systems are extremely efficient, so the rotation speed is not limited in this respect either. Therefore, in the indirect gears, and especially first and second gear, there is a real danger of over-revving if you are not careful. The huge tachometer, located in an easy-to-read position in front of the driver, has a red zone from 7000rpm.
Our test car was a brand-new car with only about 500km on the odometer, so we stayed within the tachometer’s limit of 7000rpm (which corresponds to the peak output of 110ps), but the manufacturer explained that the engine could safely reach around 8500rpm if limited to short bursts.
However, in reality, the engine’s ability to rev this high is not the most impressive thing about it. The fact is, there are very few cars that can keep up with the Cosmo even if you only use up to 5000rpm. At 5000rpm, the speeds in first, second, and third gear are about 38, 65, and 97km/h, respectively, and if you push the revs up to 7000rpm, where the red zone begins, it will reach 53, 92, and 145km/h. Even at this speed, the engine still has plenty of reserve power, and feels like it wants to keep climbing. The exhaust sound, which is close to that of a two-stroke at low speeds, changes to a unique, powerful buzz at high speeds, but it’s not loud enough to attract the attention of the police.
Due to time limitations, we were unable to take the Cosmo to the Murayama test course, so we did not get a chance to measure its performance, but the manufacturer’s official specifications claim that it accelerates from 0-400m in 16.3 seconds, goes from 0-100km/h in 8.7 seconds, and reaches a top speed of 185km/h. Even with our limited testing, these estimates seem a little modest.
Naturally, one’s evaluation of the Cosmo’s performance will vary depending on how the rotary engine’s 2 x 491cc displacement is converted into liters of conventional reciprocating engine displacement, but if we ignore the type of engine and simply consider it as a luxurious, practical, two-seater GT with a 1000cc engine, this is an outstandingly high-performance car. Especially when fuel economy is taken into account, the rotary engine’s advantage relative to reciprocating engines become even clearer. According to our measurements, the overall average fuel economy over 573km was 7.9km/l, with a best observed economy of 9.6km/l. This distance of approximately 600km was driven by a single driver with a driving technique that was far from fuel-efficient, so if performance and weight are taken into account, it can be said to be a surprisingly good result. Moreover, despite the high compression ratio of 9.4, only regular-grade gasoline is required, and no knocking was observed even when accelerating from low speeds.
The rotary-engined NSU Wankel Spyder is known to have a high oil consumption rate (121km/l, according to one test by the UK magazine Autocar). This point makes a perfect target for engineers who remain skeptical of rotary engines, so it was of great interest in this test as well.
According to the manufacturer, the Cosmo’s expected oil consumption is 2,000km/l when running continuously at speeds of 50-100km/h, and 3,000km/l in continuous high-speed driving at 150km/h. Our test car did not seem to have been specially prepared by the manufacturer, and when we checked the oil level ourselves after driving about 100km, the dipstick was at the ’low" mark. But when we put the dipstick back in and pulled it out again, it was at the full" mark, and when we carefully re-checked it at the end of the 600km test, the oil level had not decreased at all, so the oil consumption over 600km seems to be of little concern.
The 4-speed gearbox is easy to use, with good gear ratio distribution and a stubby, well-positioned gear lever with light effort and short movements. The synchro is powerful enough that it can’t be beaten even by quick downshifts. Starting off is smoother than in most sports cars, but perhaps because of the heavy 940kg vehicle weight, the rear of the car tends to sink under acceleration. The force of the clutch feels quite heavy, which is not really suitable for use around town.
As mentioned above, the rotary engine is surprisingly tenacious in the low engine speed range, but at very low rpm, such as when idling at 700 to 1000rpm, the torque seems to be much weaker than that of a reciprocating engine. For example, in the case of most reciprocating engines, if you are stopped in low gear and gently release the clutch, you can slowly move away while barely touching the throttle, or without touching it at all. But when we tried the same thing in the Cosmo, the engine always stalled.
On the other hand, as long as the car is moving, it’s possible to easily drive at exceptionally low speeds in top gear. For example, even if the speed drops to 30km/h (about 1100rpm) while still in fourth gear, the engine still runs smoothly, and if you press the throttle hard, it accelerates gradually, without any knocking. This is the kind of flexibility that you can usually only experience with a large-displacement reciprocating engine. The maximum torque is 13.3kgm/3000rpm, and 30% of that torque is available over a wide range from about 2000 to 6500rpm. This characteristic can be readily felt while driving, and in third gear, the engine gives alert, sensitive throttle response over a wide range from about 35km/h to 130km/h.
The Cosmo’s flexibility at low speeds is of course due to its excellent efficiency, but engine braking feels weak compared to a reciprocating engine. We got the impression that this may be due to the flywheel effect of the entire engine, including the two rotors themselves.
Throughout the test, the water and oil temperature gauges always stayed within the normal range (there is no oil pressure gauge, only a warning light), but immediately after driving at highway speeds the idle would sometimes rise to around 900rpm and the engine would become a little rough.
An Accommodating Ride
The Cosmo’s front suspension is by wishbones and coil springs, and the rear is a De Dion axle with leaf springs. Rather than being a performance-oriented sports suspension, is it more like that of a luxurious two-seater, high-speed practical vehicle, which is appropriate for the character of the car.
Rather than being soft, this means that the suspension stroke is quite generous. When the car hits a wavy road surface, the body moves up and down quite a lot, but the strong dampers suppress the pitching motion. The test car had Bridgestone 6.45H-14 low-profile bias-ply tires with a newly developed tread pattern, but they squealed badly when rounding street corners a little too quickly. As an option, Bridgestone 165HR-14 radial tires, which are patterned after the Pirelli Cinturato, are also available.
The rack-and-pinion steering is quite sharp. The steering effort is always light, and kickback from the road is not transmitted to the driver’s hands. The wooden steering wheel rim is neither too big nor too small. It is commendable that the length of the column can be adjusted by 60mm by manually loosening a large screw on the column. However, to achieve the popular straight-arm driving style, it is necessary to adjust the wheel as far forward as it will go, and there were complaints that the bottom of the wheel rim touches the driver’s knees when working the pedals.
The handling balance is excellent, with slight understeer continuing up to high speeds. It is also always possible to intentionally slide the rear end around tight corners in second gear, and the responsive steering makes this easy to control. However, when we went around one bumpy corner on the highway at 80km/h, the unevenness of the road surface caused the entire body of the car to jump slightly sideways.
As far as braking is concerned, our Cosmo didn’t have much going for it. The brakes are a combination of non-servo front discs and rear Alfin drums, but the pedal stroke was large and the braking effect was weak, which was a little unsatisfactory in a high-performance car with a top speed of 185km/h. There was little nose dive, and even when the brakes were applied suddenly from high speeds, there was no sign of any fade, but the pedal force was a little heavy. Many people said they thought the car needed a servo.
Later, we borrowed the car again for our photo shoot, and while the manufacturer had serviced the car in the meantime, there was no change in the feel of the brakes. The handbrake on the left side of the central tunnel is easy to use, but the stroke is long and its position when released is too high, which is bothersome while driving.
Rather unusually for a car with a differential fixed to the chassis, noise from the final drive gear is not transmitted to the interior of the car. However, every time the car was started and stopped, it made an unpleasant squealing noise somewhere in the driveshaft, similar to the noise made when the drivetrain is being overstretched. After we reported it to the manufacturer, it was fixed by the next time we borrowed the car. The test car had also been making a squealing noise from the left rear brake drum or wheel hub from the beginning of the test, and this got worse over time. Sometimes the sound would go away when the car was in motion, so we thought there may have been some contact between the brake drum and some other component in the wheel area.
Luxurious interior
The interior treatment is all black, with a small, light alloy steering wheel, wooden shift knob, and black and white checked houndstooth seat fabric adding color, creating a truly luxurious atmosphere.
The seats, made of vinyl leather with checkered cloth in the center, provide good support and can slide 140mm fore and aft. The backrest can be reclined, and the steering column adjusts telescopically, so unless you are an extremely large person, you will be able to find a comfortable driving position. The pedals are not that well-suited to heel-and-toe, but there is a footrest for the left foot, which allows you to brace yourself in hard cornering. Some people who are 176cm or taller said they would like the armrest to be moved a few centimeters forward. In the center of the steering wheel is a horn button with a large safety pad. The wooden knob of the very short gear lever falls naturally to your hand when you lower it from the steering wheel.
The instrument panel has a large speedometer and tachometer directly in front of the driver, with a water temperature gauge, oil temperature gauge, ammeter, and fuel gauge on either side of it. All are well designed and easy to read, with white markings on a black background, but when you turn the lights on at night you’ll notice that the lighting of the tachometer is the dimmest, with the speedometer next to it being about twice as bright. Even with the brightness adjusted to the highest setting, the tachometer was still too dim, and the lighting that caught our eyes the most was actually that of the radio.
The radio controls, along with switches for the two-speed wipers, adjustable horn tone (which has almost no effect), map lamp, and electric antenna are spread across the center console. This is easier to use than the usual arrangement, with the controls clustered low on the dash in front of the driver. The headlight knob is to the right of the steering wheel, next to the ignition key, but what we found particularly useful was the multi-purpose lever on the right side of the steering column. Like the one in a Mercedes, this not only controls the high and low beams and turn signals, but also operates the wipers by turning a knob on the end of the lever, and when you press the tip, an electric screen washer jet is activated. All of this can be done without removing the right hand from the steering wheel.
This may seem like a gimmick, but in real-world driving, there are surprisingly frequent occasions when you need to operate the wiper and headlights at the same time, and also dim the headlights for oncoming vehicles, which seems to be evidence that the Cosmo’s design was done carefully by people who are actually driving the car day and night. However, as mentioned above, the switch for the two-stage wiper speed is on the panel, and must be operated separately with the left hand.
As for interior space, there is a lockable glove box in the dash (which can actually hold a few small items), and a fairly large space behind the seats that can hold two small suitcases (with straps to secure the luggage). A storage compartment behind the shifter would also be useful. The trunk is spacious and has a good-sized opening, but even if you add up all this space, it probably won’t be enough for two people on a long trip.
The wide rear quarter pillars have interior air vent outlets, but the front intake only routes air to the heater, and face-level ventilation is only provided by opening the triangular windows.
Finally, regarding the body styling, aesthetics are subjective and it’s hard to say anything for sure. But among our test group, at least, the prevailing opinion is that now that it’s been three years since the Cosmo debuted at the Motor Show, it’s hard not to feel that its style is a bit outdated.
In addition, the edges of the front and rear bumpers are sharp, and the tips are more like points than rounded edges; from a safety standpoint, it would be desirable to modify this by adding rubber pads. During the test drive, the thick chrome trim around the headlights reflected light back into the driver’s eyes, and although this is a small thing, it is something we would like to see rectified.
The Cosmo is currently offered in only one specification, priced at 1.45 million yen. Toyo Kogyo has boldly provided a two-year or 50,000km warranty on this revolutionary rotary-engine super car, just like any other car. As for its durability, it is frankly impossible to say anything from this short test, but we’re sure it will improve with time.