As you may have heard, YouTuber Rob Dahm is building an outrageous third-generation (FD) Mazda RX-7 featuring a four-rotor Wankel engine. It’s an engine layout that has never been used in a production car before—every factory rotary vehicle has come with only two, at most three, rotors in its spinny-triangle engine. And, as you can imagine, building a four-rotor is way more complicated than just joining two twin-rotor motors at the eccentric shaft.
Jason Fenske of Engineering Explained is here to elucidate just what it takes to build a four-rotor engine that won’t tear itself apart the first time it’s fired up. Just as in a piston engine, the firing order has to be precisely engineered. Imbalanced combustion events will create terminal stresses, bad news for any engine, but especially bad in a high-horsepower build. Dahm is aiming for a 10,000-rpm redline in this monster rotary, so everything has to be done to exacting precision.
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The answer? A unique firing order unlike anything you’ve seen in the familiar two-rotor Wankels that prowl the streets of the world. Here’s Engineering Explained to show you the how, and the why, of this unique engine.
This story originally appeared on Road Track.