BMW Would Never Make a 500-HP Rotary i8—So Someone Else Is

The i8's greatest weaknesses are its underpowered engine and weak gearbox, so this DIY builder set out to fix it.
Jon Volk

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The BMW i8 is one of the most exciting cars to spot in public, especially if you’re into modern exotics. That said, they need more power and a much better sound to match their style. A boosted three-cylinder is great for efficiency and all, but I’m not sure anyone in the market for a machine like the i8 cares more about miles per gallon than smiles per gallon. That’s what Jon Volk set out to fix with his Bimmer by swapping in a 13B Mazda rotary engine and Audi dual-clutch transmission, and the plan is to keep the hybrid system. Spicy.

I’ve driven several i8s over the years and the only real improvement I wished BMW would have made was to give it a bigger engine. Everything about the i8’s drive is great: it handles well, it rides surprisingly comfortably, and its steering is sharp. It’s a fun little mid-engine sports car, built on a carbon fiber chassis, with stunning good looks. But its 1.5-liter turbocharged three-cylinder and hybrid assist always lacked the excitement that its looks suggest. Volk swapping in a far more powerful and interesting engine is like my personal dream come true, though his setup is far more ambitious and interesting than anything I could have dreamed up.

Volk bought the i8 specifically for this build. He’s taken on some big projects before, including a Tesla-swapped E30 we featured back in 2019. He wanted something he could drive daily, take to the track, and even use at the drag strip. But since he also has a family, it had to be capable of hauling two kids around. Finding a mid-engine car with back seats isn’t the easiest of tasks and his choices boiled down to the i8 or Lotus Evora. While the Evora might be the more typical enthusiast choice, he wanted something more interesting—something with more of a challenge—so he went with the i8. He knew he wanted to swap the puny three-pot with something more potent but didn’t know what until he got under its hood and realized just how little space there was.

The BMW i8’s chassis is set up for a compact power plant. That means there’s little room for anything bigger than the Mini-sourced three-cylinder engine without making extensive engine bay modifications. And you know what sort of engine is ultra-compact but also capable of making big power? The 13B-REW rotary engine from an RX-7, of course.

Volk couldn’t just drop any old 13B in there, though. His is heavily modified with a large street port, half-inch tension studs, and lightened, balanced S4 low-compression rotors, among other mods. To make it bespoke for this project, he 3D printed the intake manifold and charge pipe from black aluminum and even added a “TwinPower Turbo” badge to make it look like a stock BMW part. While he doesn’t have an exact power figure, he thinks it should make around 500 horsepower after it’s tuned. Add in another 130-ish horsepower if he can manage to keep the front electric motor’s power figure the same after calibrating it all.

Since the 13B is a small engine, Volk didn’t need to modify any part of the hybrid powertrain to fit it. Every wire, coolant line, and bracket for the hybrid system is exactly the same as the stock.

However, the biggest change Volk made was the transmission. He threw out the i8’s factory six-speed Aisin automatic, which he calls “absolute garbage.” According to Volk, the stock transmission’s ability to handle power is so poor that the engine software drastically limits torque output in the first few gears. BMW even caps launch control usage to 100 times total, meaning once it’s been launched 100 times, that’s it.; it won’t allow anymore. He ditched that old gearbox for the seven-speed dual-clutch transmission from an Audi RS3. Interestingly, the new dual-clutch didn’t need much modification to fit.

The project isn’t fully built yet, and the swap is still in-progress. However, Volk has everything mapped out, measured, and ready to go. He hopes to have it finished and ready for its debut at the Grid Life event at Lime Rock Park in August. Ideally, it will be track-ready by then but, if not, he hopes it will at least be ready for public viewing. I can’t wait to see the final build because it’s one of the most unique projects I’ve seen, and it has the potential to be the car I’d always dreamed the i8 could be.

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