6th December 2019

Mazda RX-7, the rotary revolution

The first-generation Mazda RX-7 was a real trailblazer. With a beautiful, svelte teardrop design, Mazda decided to shun convention by opting for a rotary engine, which would remain a characteristic of the car throughout its three generations.

Unveiled in 1978 for a ’79 launch, the main talking point of the FB (as the first generation was known in Europe) was its adoption of Felix Wankel’s rotary engine design, which at launch was the perfect complement to its design and driving dynamics. The tiny 12A rotary, as it was designated, was mounted behind the front axle, was roughly a third of the size of a conventional piston engine producing similar power and, fed by a Nikki carburettor, provided up to 117bhp from its 1146cc capacity (plenty more if you found an Elford Turbo conversion). This enabled a low centre of gravity, perfect weight distribution and contributed to superb handling limited only by the lack of rack-and-pinion steering.

The Wankel rotary eliminates a lot of the moving parts associated with an internal combustion engine in a quest for smoothness and performance. The motor is referred to as a ‘twin-rotor’ design, which references the use of two rotors spinning on an eccentric shaft within two housings. The intake and exhaust ports are on the same side, above each other, with the spark plugs on the opposite face of the housing. As a fuel and air mix is injected into the housing, the rotor spins eccentrically to create chambers for intake and compression, combustion, and exhaust. It’s a beautifully simple design that promotes high-revving performance. Think about the forces involved with a high revving internal combustion engine with the con-rods and pistons moving up and down on the crankshaft. Round and round is a lot more efficient than up and down.

The downside of the design was initially perceived as being reduced fuel economy and oil consumption (a small amount is injected into the housing to lubricate the rotor tips), but advancing years earned the RX-7, perhaps unfairly, a reputation for poor reliability. Wear to the housing or rotor tips in particular will lead to reduced compression and poor – if any – running, which means it is not resilient to poor maintenance. Thankfully, plenty have survived and there is the expertise to not only rebuild the rotary engine, but to extract a lot more power from its compact size through porting, or by increasing the rotor count.

The FB RX-7 itself was available in Series 1, 2 and 3 iterations before the second generation, the FC, was launched in 1986. Each Series brought revisions to body styling, interior specification and options, including a limited-slip differential, body mouldings and front and rear spoilers. A commonality was the fitment of an audible buzzer that sounded as a reminder that you were enjoying the rotary engine too much and were rapidly approaching 7000rpm and imminent licence endorsements. With no increase in harshness at high revs, Mazda deemed the buzzer an essential, and it was probably right.

Are you sad to see the demise of the rotary engine? Perhaps you’ve covered tens of thousands of trouble-free miles behind the wheel of an RX-7? We’d love to hear your rotary versus piston arguments in the comments.