Rob Dahm’s Single-Rotor Turbo Miata Hits 155 HP on Dyno: A Scratch-Built Wankel Engine Build

You’ve likely heard of Rob Dahm’s 12-rotor engine with three turbos, but his latest project is the polar opposite: a single-rotor turbocharged Miata. Dahm has documented the build on his YouTube channel over the past year, and the results are nothing short of rowdy. In fact, pushing the engine hard enough could grenade the rear differential.

This Miata build has become one of the most engaging projects on YouTube. The engine is almost entirely constructed from billet aluminum, weighing just 70 pounds. A Garrett GBC-22 turbo with an internal wastegate powers the setup, complemented by a 3D-printed intake manifold—a necessity given the rarity of off-the-shelf options.

Dahm has been actively driving the single-rotor Miata for the past five episodes, dedicating significant effort to tuning. The engine still requires substantial fuel delivery adjustments, but progress is evident. After transporting the Miata to Westech Performance, the team conducted dyno testing, revealing impressive figures.

Dyno Results: 155 HP and 136 lb-ft of Torque

The Miata’s one-rotor engine produced a best result of 155 horsepower and 136 lb-ft of torque. These figures are remarkable for a scratch-built project with minimal displacement. Dahm believes the engine has even more potential once the fuel delivery issues are resolved.

Ongoing Challenges and Future Improvements

The build isn’t yet polished, but Dahm has identified key issues. Boost creep from the internal wastegate causes sudden pressure spikes up to 22 psi, which appear to force fuel into the oil catch can. Addressing clearances, gaps, and turbo tuning should significantly improve performance, transforming the Miata into a strong runner.

Why This Build Is Impressive

“I respect it one way or another. I could never put something together like this, and honestly, who cares how much power it makes? A functional turbo one-rotor is impressive. The fact that it can power a Miata down the highway is icing on the cake.”

While the project remains a work in progress, its engineering prowess is undeniable. The Miata’s ability to hit the road under its own power highlights the viability of a single-rotor turbo setup.

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