Yes, There Is A 12-Rotor Engine — Here's How Much HP It's Trying To Push

Wankel engines first saw use in production cars as early as 1964 — and not even in a Mazda, but rather in an NSU. That little single-rotor powerplant quickly evolved into the more typical two-rotor design one might see in a Mazda RX-7, for example. Then came a three-rotor, which first appeared in the Eunos Cosmo, before peaking with the massively powerful four-rotor in the 787B Le Mans race car, one of the greatest rotary engines ever fitted to a vehicle.

This is possible because of the way a Wankel engine is constructed, with each rotor in its own housing. So you have an engine configuration similar to, say, a radial with multiple cylinder banks, leading to custom-built Wankel engines housing increasingly alarming numbers of rotors. Enter Rob Dahm, with his quite-frankly-insane creation built by Tyson Garvin currently holding the undisputed heavyweight title within the Wankel community: a massive, 12-rotor, tri-turbocharged monstrosity.

Dahm claims that he hopes for a grand total of 5,000 horsepower on methanol fuel. Yes, that's 5,000, with a comma after the five. The only non-jet engines to even touch similar numbers sit in purpose-built drag racers, marine applications, power generators, locomotives, and so on. This engine effectively transcends the definition of an "automotive powerplant," and putting it in a car would be like fitting it with two of the four engines powering the record-breaking "American Ethanol" powerboat racer. So just what is this utter beast of an engine, and how does it produce so much power? Let's check it out in some more detail.

Originally designed as an alternative to a big-block Chevy for powerboat racing, this massive engine contains three four-rotor banks in a single assembly made to fit the space normally occupied by a big-block. Each bank links together to a common output shaft via gears, producing an engine that's actually compact enough to fit into something drivable — in Rob's case, his custom-built dragster.

At first, 5,000 horsepower sounds entirely ridiculous for any engine, much less a rotary engine. But it's actually far more feasible than one might expect. Let's take the Mazda 787B's R26b, as an example. This engine produces about 690 horsepower in race-trim, a power figure it achieves from just 2.6L (654cc per rotor) of naturally aspirated engine. That is a truly astounding power/weight ratio. By comparison, the Jaguar's racing V12 produced a little over 700 horsepower from 7.0L. Rob Dahm's engine effectively mates three of these engines to a common shaft and then turbocharges each bank on top of that. This one-off design is not only the engine with the single highest rotor count in the world, but perhaps soon also the fastest rotary engine, period.

Rob Dahm remains hard at work perfecting the engine's capabilities, though the monstrous unit requires a lot of improvising to even start in the first place, much less run at full tilt. It's a long and tedious process which he meticulously documents on his YouTube channel, culminating in the ongoing development of what he plans to be the world's first 5-second rotary dragster. If any rotary can get it done, it'd certainly be this one.