Here's an example of an engine we couldn't really include in the Workhorse Engine of the Day series, because in spite of its incredible power-to-weight ratio and overall screamin' glory, the rotary engine is just not bulletproof enough to be considered a true workhorse. All that's changed with the new EOTD series, however, and we can now celebrate the nonreciprocating awesomeness that is the Mazda 13B. In truth, all the Mazda Wankels are variations on the same design; we just selected the 13B as the flavor that was built for the longest period, 1973 through 2002. Cosmos, RX-7s, 7-second Starlets, you name it, the 13B has powered it. Make the jump for our favorite hypnotic GIF animation. [Mazda, Wikipedia]