During the 85th edition of the 24h of Le Mans in 2017 the rotary engine will return to this legendary track, more than 25 years after it has been banned from endurance racing. The Hybrid IM01 racecar will use a rotary engine as range-extender in order to complete the 24 hours. Because the rotary engine will be used as a generator, it can be tuned in such a way that it always runs in its optimal operation point. This results in a tremendous reduction in fuel consumption, as has been shown on the InMotion engine test bed located at the University of Technology Eindhoven.
In 1991, its final year of admission on the Le Mans racetrack, the rotary engine yielded Mazda a remarkable result. They won the 24h race with the Mazda 787B. This enormous success unfortunately also meant the end for this type of engine. Motorsports Federation FIA reacted by banning the rotary engine from its races. The piston engines couldn’t keep up with the reliability and the power vs. weight ratio that a rotary engine offers. Exactly those kind of regulations, which limit technological innovation, are the primary reason that InMotion began developing the IM01.
The IM01 can use the rotary engine, because InMotion will compete with it in Garage 56. This class within the 24h of Le Mans embraces technological innovation. Besides the regulations on safety, no other technical limitations exist in this class.
Characteristic advantages of a rotary engine are compact sizing, because of which it requires little space in the car and weighs less than a comparable piston engine, high output power (this will be around 545 HP for the IM01) and few moving parts. These advantages are particularly useful for a racecar.
The best known disadvantage, wear due to the angles of the rotor, has already been solved a couple of decades back. Another disadvantage of the rotary engine, which still exists today, is the relatively bad efficiency at different engine speeds. This is where the series-hybrid drive-train of the IM01 comes in. Because the rotary engine acts as a generator for electricity, the engine can be tuned in such a way that it always operates at the optimal engine speed. This results in an enormous improvement in efficiency.
The innovation of the IM01 doesn’t stop here however. InMotion is currently running tests on an engine test bed with an adjusted combustion principle, called partially premixed combustion (ppc), which will also be applied on the IM01. The result of applying ppc on a rotary engine improves the efficiency even further. This yields an engine which will be around 45% efficient. Compared to regular piston engines, which have typical efficiencies of around 25%, our engine is almost twice as efficient. In shorthand this means that we will be able to finish the 24h of Le Mans using just over half the fuel that a normal racecar would.
After just over a year of scientific research on the range-extender for the IM01, the engine is currently running on our test bench. With our current set-up we have the possibility to simulate a 24h race, tune the engine to its optimum and test various developments. And that is the reason why the return of the rotary engine to Le Mans is closer than you’d think.