Forget Mazda, Rolls-Royce made a rotary and can you believe it was a diesel?

At one stage the 'Wankel' rotary engine could have been applied to multiple cars and even military vehicles.

During the '60s and '70s everyone wanted in on the rotary. You know, the tiny powerplant that use less moving parts than a conventional piston engine, but creates huge amounts of power per litre.

Ford, GM, and Mercedes-Benz were in on it. Even Citroen was playing around with rotary tech, but it was Rolls-Royce that wanted to apply the futuristic design in military vehicles, such as trucks and tanks.

However, by the time the mid-'70s rolled around - with its super-fun oil crisis - Mazda was the only player left investing in the rotary engine, which is a pity because Roll-Royce was developing a very interesting Wankel diesel.

Unlike the conventional rotary engine, Rolls-Royce's prototype consisted of the rotor housing placed on top of each other instead of in-line as with Mazda's units.

The bottom rotor was larger than the top one and acted purely as a compressor for the upper part of the engine which produced power.

If the rotary wasn't unique enough already, let's add two different sized rotors. (image credit: RX7club)

But how exactly does it work? Well, air enters the first chamber, and is compressed by the large rotor before being sent to the second chamber for detonation after the diesel is introduced to ignite the fuel before sending the exhaust down into the first chamber.

Over a six-year period (1966-72), Rolls-Royce drew up 30 different combustion chamber shapes, six fuel injector positions and over 100 arrangements before settling on this design.

Ultimately only four prototype engines were produced. The first engine (called the R1) had a compressor size of 1126cc while the combustion was rated at 500cc and made 37kW (50hp).

The R2 used a three-stage layout which was Roll-Royce's back-up design and was never fully investigated.

The R3 went back to the two-stage system and could make 134kW (180hp) at 4500rpm.

The last engine, 2-R6 had a combustion chamber of 1265cc and compressor chamber of 3250cc resulting in 261kW (350hp).

Weighing in at 425kg and producing 350hp, this rotary has an impressive power-to-weight ratio. (image credit: der-wankelmotor.de)

Due to the project placing a financial strain on the company, Rolls-Royce pulled the plug on the radical design, and the engines never saw the light of day.

However, I'm sure (after reading this) a madman is out there watering at the idea of engine swapping a Wankel diesel into a Roll-Royce or RX-7.

Would you like to see a rotary engine in Rolls-Royce's current cars? Let us know in the comments.