Gear and Tech : January 29, 2009

What the hell is a Rotary Motor anyway? What’s all this about rotors and NO PISTONS!? Blasphemy! Actually, it’s quite simple really. As opposed to a piston motor which has a Compression and Ignition phase for each cylinder, the Rotary does it all in one rotation of the triangle shaped rotor.

Advantages

The Rotary Engine is very simple. It’s a motor design that utilizes way less moving parts than it’s piston counterpart. The 13B-MSP Renesis (from the RX8) has the highest horsepower per displacement of any naturally aspirated motor produced from the Factory in America. For it’s size, the rotary packs a punch. For reference, the 13B from the RX8 is a 1.3 liter, and produces 232 horsepower. That equates to a ridiculous 178 horsepower per liter. In Theory, that would be equivalent to a 6.0 liter LS2 (from the Corvette) producing 1068 horsepower N/A from the factory.

Unlike Piston engines, Rotaries are almost immune to catastrophic failure. In a piston motor, you can have a piston seize and cause all kinds of damage, but in a Rotary motor, while the engine will lose power, it will continue to produce a limited amount of power until it finally dies.

Rotaries will also rev to the moon and still make power. For instance, A RX8 redlines at 9k and that’s where it makes peak power as well. Needless to say, the Rotary likes to stay high in the RPM range.

Disadvantages

Some main complaints of the Rotary are gas mileage and burning oil. One of the most common misconceptions is that the Rotary engine burns oil out of fault, this is not necessarily true. The Rotary uses oil squirters that take small metered amounts of oil and mix it into the fuel to lubricate the seals. Gas mileage is very Mehhhhh at mid 20’s (supposedly….much less in reality.)

Rotaries also tend to produce about as much torque as a screwdriver and seals tend to be a big problem after a while if you live in a colder climate. Parts are generally expensive and since it’s a Rotary, you have to take it to rotary mechanic or dealership to get it worked on when something goes awry.

Rotaries sometimes have a problem flooding with fuel on cold starts as well. This generally only happens with older 13B’s, so it’s necessary to let the motor warm up to operating temperature before you decide to take off.

All in all, the rotary has it’s ups and downs, just like everything else. Nothing can really match the sound of a 26B sounding like a huge cammed V8 at idle and then revving up like a streetbike. Hopefully this article was informative and cleared up some misconceptions. Rotaries may be different, but they’ll always have a place in my heart.