It’s the most mundane and magical thing in the world: getting a vehicle to turn on and move forward. This little miracle is powered by a potent mix of some of our basic elements—get air, water, and fire in the right place at the right time, and races can be won.

For most cars, that right place and right time can be reduced down to one

part

: a piston engine. But some cars get their giddyup from a different source.

Jerry

, the

car ownership super app

, breaks down how a rotary engine works.

An engine primer

Let’s zoom out before we examine the particulars. If you own a gas-powered car, you’re getting where you’re going because of internal combustion, explains

HowStuffWorks

. Gas is burned (“combustion”) inside (“internal”) the engine and the ensuing energy is then captured and used as power. (Internal combustion branches into gas and diesel, but the process is largely the same for both.)

Now we can zoom in a bit. Capturing energy and converting into power works on a four-stroke cycle in most gas-powered engines, says HowStuffWorks. Intake, compression, combustion, and exhaust comprise the four-stroke cycle, and when this cycle is repeated in quick intervals over and over again, the explosions of energy from the compressed air and gas create enough power to keep a car in motion.

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Piston engines

Though different in look and performance, piston and rotary engines share the four-stroke cycle in common. A piston engine uses pistons, cylinders, and crankshafts to get the job done.

A helpful animation from

Car Throttle

illustrates the process. When the piston travels downward inside the cylinder, air enters through the intake valve and fuel is added as well. As the cylinder makes its way back up, the mixture of fuel and air is compressed, which makes it very hot.

This very hot mixture then ignites via spark, which forces the cylinder back down. On its way back up, the now-spent mixture is then pushed out through the exhaust valve, and the cycle is complete.

The cylinder is attached to a rotating crankshaft, which means that each time this process accomplishes step four, the crank is already bringing everything back to restart at step one. And the crankshaft is linked to the wheels and conveniently already going in circles, HowStuffWorks points out, which is exactly what we’re asking the tires to do.

Rotary engines

A rotary engine applies the exact same four-stroke cycle, but it puts the clothes through a different washing machine to get them clean. This type of engine, which Car Throttle calls the “black sheep of the engine world,” looks like the top of a grandfather clock, except with a floating triangle instead of a face.

This floating triangle, the rotor, is the cylinder from the piston engine. As the rotor turns in the rotor housing, it covers up and then unlocks the valves in the corners, which allows the exact same cycle to take place—air and fuel in, compression via rotor squishing against the wall, combustion from the lack of space for the trapped elements, and then escape via exhaust as the rotor unpeels itself from the exhaust valve and circles back to the intake.And the car indeed goes.

MORE: Rancho vs. Bilstein: The Best Shocks for Your Car

Who’s in the rotary club?

Piston engines are generally favored because they don’t burn much oil, says Car Throttle, and they have quite an efficient combustion cycle, which means fewer emissions. However, you’ll have to live with a limit on the amount of revs you can spin up with a more methodical piston engine.

Rotary engines, by contrast, are compact and have very few parts to keep track of, which means an easier time generating a ton of revs. Plus its small size is an invitation to throw it in any old engine bay that you want.

Unfortunately, if you do add one to your restored car, you’ll be burning a lot of oil to keep the process running smoothly, and risking the dreaded “blown apex seals,” where the rotor housing and the rotor will no longer kiss and make up. This too-much-space problem evinces much more exhaust and occasional flames, says Car Throttle.

Mazda

decided to live with that for a few of their wares, because it wanted the “superior power to weight ratio” that comes from a light, little rotary engine. It cites four famous rotary-powered cars, including the beautiful 2003 Mazda RX-8, all of which lived to tell the tale because engineer Kenichi Yamamoto and his team figured out an answer to the apex seal issue that plagued other carmakers: they sealed the engines with graphite aluminum alloy.

This fix made the rotary engine a legend for the brand, and now every carmaker who settles for pistons has to ask themselves—should we be so concerned about possible flames, or can we give the people what they want?

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