You’ve probably heard the sound. It’s not the low-frequency rumble of a V8 or the clinical whine of a modern turbocharged four-cylinder. It’s a high-pitched, angry buzz that sounds like a swarm of metallic hornets trapped in a tin can. That is the 13B. Specifically, the rotary engine in RX7 models that has spent the last few decades turning sensible mechanics into frustrated poets and speed demons into debt-ridden enthusiasts.
It's weird.
Most engines use pistons that go up and down. They’re reciprocating. You have a heavy hunk of metal flying one way, stopping, and then flying back the other way. It’s violent and kind of inefficient when you think about the physics. Felix Wankel looked at that and decided a triangle spinning in a housing was a much better idea. He was right. And he was also very, very wrong.
The Magic and the Nightmare of the 13B
The rotary engine in RX7 cars is basically a triangular rotor spinning inside an epitrochoid-shaped housing. Think of a fat peanut. Because there are no valves, no camshafts, and no timing belts to snap, the engine is tiny. You can literally fit a 250-horsepower 13B-REW in a large suitcase. This is why the FD RX7 handles so well; the engine sits behind the front axle, creating a front-mid-ship layout that makes the car feel like it’s pivoting around your belly button.
But here is the catch. The seals.
The apex seals are the tiny strips of metal at the tips of the rotor. They have to keep the combustion gasses contained while sliding across the housing surface at thousands of RPMs. If they fail, your compression vanishes. Your engine becomes a very expensive paperweight. Most owners treat 60,000 miles as the "danger zone." Honestly, if you make it to 100,000 miles on an original engine without a rebuild, you should probably buy a lottery ticket.
Boost and the Sequential Headache
When Mazda released the FD (the third generation), they didn't just stick with a naturally aspirated setup. They went for a complex, sequential twin-turbo system.
The idea was smart: use a small turbo for low-end torque and a big one for the top end. In practice? It created a "rat's nest" of vacuum lines under the hood. There are over 60 feet of black rubber hoses in there. If one of them gets a tiny crack from the massive heat the rotary produces, the whole boost pattern falls apart. You get a "dip" in power at 4,500 RPM that feels like the car just tripped over its own feet.
Many tuners just rip the whole thing out. They go "single turbo." It’s simpler, more reliable, and lets the rotary engine in RX7 breathe properly. But you lose that instant-on torque that made the car famous in the first place. It’s a trade-off. It’s always a trade-off with these cars.
💡 You might also like: Formula for the Area of a Cylinder: Why Most People Get It Wrong
Why Does It Drink So Much Oil?
If you buy an RX7 and don't check the oil every other time you fill up with gas, you're going to have a bad time. The engine is designed to "burn" oil.
Mazda engineers built an Oil Metering Pump (OMP) that literally injects a tiny bit of engine oil into the combustion chamber. Why? To lubricate those apex seals I mentioned earlier. Without it, the metal-on-metal friction would kill the motor in minutes. This means you aren't just burning gas; you're burning your 10W-30.
Pre-mixing: The Secret Sauce
Ask any "rotary head" about pre-mixing. They’ll look at you like a member of a secret society. Basically, because the stock OMP can fail or provide uneven lubrication, owners pour two-stroke oil directly into the gas tank. Yes, like a lawnmower. It sounds ridiculous for a high-end Japanese sports car, but it’s the single best thing you can do for the longevity of a rotary engine in RX7 applications. Idemitsu actually makes a specific rotary premix that is the gold standard in the community.
Thermal Management is the Real Boss
The rotary runs hot. Like, "melting plastic connectors under the hood" hot.
The exhaust gas temperatures (EGTs) are significantly higher than a piston engine because the exhaust port opens so quickly and the combustion cycle is so fast. This is why the stock pre-catalytic converter on the FD RX7 is often called a "ticking time bomb." It holds heat right against the engine. Most experts, like the late legendary tuner Rick Engman or the guys at Racing Beat, will tell you the first modification should always be a downpipe and a better radiator.
If you overheat a rotary once, you usually warp the housings. In a piston engine, you might just blow a head gasket. In an RX7, you’re looking at a full teardown.
The Sound of Brapping
You’ve heard of "bridgeporting" or "peripheral porting." This is where you enlarge the intake and exhaust ports to let more air through. Since there are no valves, the port shape determines the "timing." A heavy bridgeport results in that iconic "brap-brap-brap" idle. It sounds cool, sure, but it also makes the car almost undriveable in traffic. You lose all your low-end vacuum. You have to rev it to 2,000 RPM just to pull away from a stoplight without stalling. It's a race-car modification that people put on street cars because it sounds aggressive.
✨ Don't miss: Who Will Be the First Black Person on the Moon? The Artemis Reality
The Misconception of Reliability
Is the rotary engine in RX7 unreliable? Sorta.
It’s actually very robust in terms of moving parts. There are only three main moving parts: two rotors and an eccentric shaft. Compare that to dozens of valves, springs, retainers, and pistons in a V6. The rotary won't throw a rod through the block very often.
The "unreliability" comes from the fact that it is incredibly sensitive to maintenance. You can't be lazy. You can't skip oil changes. You can't ignore a cooling leak. Most of the "blown engines" you see on Facebook Marketplace are the result of owners who treated them like a Toyota Corolla. You cannot treat a 13B like a Corolla.
Flooding: The Quirky Death Sentence
Here is a fun fact that ruins many people's mornings: if you start a cold RX7, move it ten feet in your driveway, and shut it off immediately, it will probably "flood." The engine injects a lot of fuel for a cold start. If you kill the ignition before that fuel burns off, the spark plugs get soaked. Because the rotary has lower cranking compression than a piston engine, it won't fire back up. You have to pull the fuel pump fuse, crank it to blow out the gas, clean the plugs, and pray.
The Current State of the 13B
In 2026, finding a clean rotary engine in RX7 is getting harder. Parts are becoming expensive. Mazda started a heritage program to reproduce some bits, but housings are still pricey.
Yet, the community is thriving.
👉 See also: J. Robert Oppenheimer: What Most People Get Wrong About the Father of the Atom Bomb
New technologies like billet housings and better ceramic apex seals are making these engines hold 500+ horsepower more reliably than they ever did in the 90s. Companies like Adaptronic and Haltech have created ECU "plug and play" kits that manage the engine much better than the ancient 16-bit computers Mazda used.
Actionable Steps for the Aspiring Owner
If you are actually looking to buy an RX7 or currently own one, don't just wing it.
- Get a Compression Test: Not a standard one. You need a rotary-specific compression tester that shows the pulses for all three faces of the rotor. If one face is low, your apex seal is on its way out.
- Upgrade the "Cooling Stack": Before you buy fancy wheels, buy an aluminum radiator and a dual oil cooler setup if you don't have one.
- Delete the Pre-cat: Replace the stock start-up catalytic converter with a high-flow downpipe. It drops under-hood temperatures by a massive margin.
- Premix Every Tank: Use a high-quality JASO FD rated two-stroke oil or a dedicated rotary premix. Half an ounce per gallon is the typical street ratio.
- Let It Warm Up: Never, ever beat on the car until the oil is up to temperature. The coolant needle might move fast, but the oil takes longer.
- Redline It Often: There’s an old saying: "A redline a day keeps the carbon away." Rotaries suffer from carbon buildup on the seals. Taking it to the 7,000+ RPM buzzer (once warm) helps blow that gunk out.
The rotary engine in RX7 is a demanding, thirsty, hot-running masterpiece. It isn't for everyone. But the first time you hit 8,000 RPM and feel that smooth, electric-like power delivery, you'll understand why people are willing to put up with all the drama. It's a mechanical soul that nothing else can replicate.