Monster. That’s the only word you need to describe the one-of-one 12-rotor engine Rob Dahm is building. We’ve already heard it run, albeit without the three turbochargers installed. Progress is being made, as seen in this recent video where the engine goes to a dyno for some testing.
Technically, this isn’t a new engine. It was built years ago by a man named Tyson Garvin, at which point it allegedly could spin to 10,000 rpm and belt out 1,400 horsepower, all while being naturally aspirated. It also made 800 pound-feet of torque at a measly 2,000 rpm, but nothing was ever official.
Garvin turned the engine over to Dahm, who has a bit of experience in the rotary world. He’s had it since 2023, and it hasn’t been sitting in a corner collecting dust. It’s been completely redone and boosted with three massive turbos, which brings us to the above video.
Simply getting the engine hooked up to the dyno was a challenge. After (barely) getting it through the door, it couldn’t bolt to the dyno rig with the existing hardware. So a custom adapter was milled to make it work. There were also concerns about keeping things safe in case of fire, simply due to all the various components on the engine. To further air on the side of caution, these pulls were essentially naturally aspirated, with all the boost being vented out. And the maximum rpm limit was set to 4,000 revs. In short, it’s a baseline proof-of-concept session.
Quite the baseline, then. Dahm said the engine actually started building boost at 4,000 revs under load, something he didn’t expect. It died out on the first pull after running lean; on the second pull with more fuel added he recorded 750 lb-ft of torque at 3,500 rpm. That was done with the wastegate open, so boost wasn’t a factor. The numbers support Garvin’s figures from so many years ago.
Unfortunately, we don’t get any more dyno action after that. This massive engine has a problem starting—not because of fuel mixtures or something electrical, but because it’s simply so big that it burns through starters trying to turn over. Dahm ultimately gets a special diesel-engine starter fabbed up that seems capable of doing the job. And that’s where the current chapter of the 12-rotor ends.
The next video will hopefully push things to the limit. With gobs of torque at lower RPM without any boost, it should truly live up to its status as a monster motor.
Source:
Rob Dahm / YouTube
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