It’s been almost 30 years since rotary engines were allowed in the 24 Hours of Le Mans race. Now, thanks to a subtle rule change, announced with literally zero fanfare, rotary engines are back.
Mazda won the 1991 Le Mans with a rotary engine, but such engines were effectively banned by the 1992 running of the race. Although they weren’t outright banned, the rule changes quite literally prevented rotary engines from competing. They’ve stayed banned ever since. However, they will finally be allowed back for the 2021 version of the iconic race.
Interestingly, neither the organizers of Le Mans or the Federation Internationale de L’Automobile (FIA) — the organization that governs most major auto racing — bothered to announce it publicly. Even Mazda, with their past rotary engine success, didn’t bother to comment on the rule change.
Instead, it took Craig Scarborough, a genius when it comes to the technical aspect of race cars, pointing it out on social media.
Rotary engines are allowed in the hypercar regs 👍 https://t.co/4tM5v4OJqT
— Craig Scarborough (@ScarbsTech) December 11, 2019
1.13 Engine cubic capacity
The volume swept in the cylinders of the engine by the movement of the pistons. This volume shall be expressed in cubic centimetres. In calculating engine cubic capacity, the number Pi shall be 3.1416.
In the case of a rotary engine, the engine cubic capacity is the volume determined by the difference between the maximum and minimum capacities of the combustion chambers.[…]
1.33 Rotary engine
Engine of the type covered by the NSU Wankel patents.[…]
220.127.116.11 Bespoke engine:
• Variable geometry devices are not allowed except for rotary engines.
• Engine must not have more than two inlet and two exhaust valves per cylinder.
– Only reciprocating poppet valves with axial displacement are permitted.
– The sealing interface between the moving valve component and the stationary engine component must be circular.
– Electromagnetic and hydraulic valve actuation systems are forbidden.
18.104.22.168 Engine of the make:
The engine of the make is a series engine. that meets the following conditions:
• At least 25 identical engines identical to the ones destined for a series production car homologated for road use equipped with this engine must have been produced;
At least 25 identical series production car homologated for road use equipped with this engine are produced by the end of the year of the first season this engine is competing in.
At least 100 identical series production car homologated for road use equipped with this engine are produced by the end of the year of the second season this engine is competing in.
The series engine is homologated with FIA/ACO.
One complete engine is deposited with the FIA/ACO.
5.8 Engine fuel systems
5.8.1 No fuel injectors are permitted downstream of the exhaust valves or of the exhaust port inlet on a rotary engine.[…]
5.9 Ignition systems
5.9.1 With the exception of rotary engines, the ignition is only permitted by means of a single ignition coil and single spark plug per cylinder. No more than five sparks per cylinder per engine cycle are permitted.
The use of plasma, laser or other high frequency ignition techniques is forbidden.[…]
5.14 Materials and construction – Components
5.14.1 Pistons must respect Article 5.13. Titanium alloys are not permitted. Rotor seals on rotary engines may be manufactured from a ceramic material.
If you don’t understand why this a big deal, allow us to attempt an explanation. Rotary engines are a distinct alternative to the “standard” piston engine. As explained in this inforgraphic, rotary engines are often more powerful, lighter, and faster than piston engines. They have fewer moving parts, meaning they are more durable and reliable. The main problem with rotary engines is not with their performance, but with their environmental impact. They consume plenty of oil and struggle to meet emissions standards, especially in consumer vehicles.
The previous banning of rotary engines killed off the Group C era of racing. Perhaps this change is the dawn of a new era of hypercar racing? At the very least, Mazda should be excited.