Rotary Legend Abel Ibarra Assembling Rob Dahm’s Mazda 20B 3-Rotor

We’ve shown you videos of awesome Wankel Rotary engines before, and we’ve even shown you how its unique design works, from the inside of the combustion chamber. However this particular video features two of the largest names in the modern-day rotary engine world. The engine belongs to internet sensation and avid rotor-head Rob Dahm, and the engine is being assembled by the legendary rotary performance specialist and drag racer Abel Ibarra.

While this may not be Dahm’s largest or most extravagant rotary project, as he has some truly crazy projects under his belt, this one definitely has a special place in his heart. He’s had this particular Mazda 20B three-rotor engine powering his black FD3S RX-7 for almost a decade, and abused it mercilessly, logging dyno sheets between 750 and 950 horsepower along the way.

The engine was in really poor shape when it arrived at Ibarra’s shop, with dented rotors, destroyed apex seals causing scored rotor housings, destroyed corner seals leading to scored side housing faces, and cracks in the iron side housings themselves, from the engine actually twisting under load.

This is about as much detail as you’ll ever see of Ibarra’s intake port work, without paying him to work on your rotary. Besides increasing flow like traditional porting, altering the port size and shape on a rotary is like changing the specs on a camshaft lobe as far as lift and duration.

After resurfacing all the housings, and replacing some of the rotors, Ibarra went to work with a little bit of his magic port work. So magic, in fact, that you’ll see the intake ports blurred out in the video. More than just the equivalent of porting your intake and exhaust ports on a standard piston engine, changing the size and shape of the intake and exhaust ports on a rotary are akin to changing the lift and duration, as well as lobe shape on a camshaft. Just like some builders won’t share cam specs, it makes sense that Ibarra plays his cards close to the vest.

In addition to the port work, Ibarra also doweled the side irons, which is exactly what it sounds like. By machining out room for extra thick locating dowels, the engine will better resist the torsional forces which previously caused the side irons to flex enough to cause cracking.

In addition, Ibarra made a modification to the irons, so that if they do crack again, the oil will be contained, and keeps the engine from oil starvation. The new rotors have new corner seals and Ibarra has upgraded the apex seals to more robust 3mm units.

So sit back, relax, and watch this Mazda 20B three-rotor be assembled by one of the most experienced set of hands on this continent. If you’re a rotor-head, this is zen. If you’re not, pay attention, you might learn a thing or two about “those funny engines without pistons.”

It’s hard to imagine that this relatively diminutive engine packs upwards of 900 horsepower. While rated from the factory as a 2.0-liter engine, there is some debate as to how the measurement of a rotary’s displacement should occur. If measured using the traditional piston engine method, it would come out to 6.0 liters.

About the author

Greg Acosta

Greg has spent over a decade in automotive publishing as Senior Editor of Race Pages magazine. In his free time, he is a firearms instructor and volunteer in the police armory.
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