Rotary Engine Reliability Issues and How to Resolve Almost All of Them

Rotary engines are the underdog of the car world. They aren’t as exciting as big blocks and LS engines, but they have a unique driving experience and sound that makes some car enthusiasts swoon. The rotary engine became popular with Mazda, particularly the Mazda RX-7 and RX-8 — both features in the Fast and Furious franchise. But, Mazda has long since let go of manufacturing the rotary engine, and there aren’t many mechanics today that have the knowledge and know-how on repairing the common issues these engines often face. Rotary engines are known for being typically unreliable, but the issues are somewhat easy to resolve.

Carbon deposits are one of the biggest problems rotary engines face

Mazda RX-8 rotary engine coupe engine bay
Mazda RX-8 rotary coupe engine bay | TOSHIFUMI KITAMURA, AFP, Getty Images

All internal combustion engines are faced with the issue of carbon deposits, which occur in the process of the combustion of gas. It’s a natural byproduct of the chemical reaction that really can’t be avoided, but it is a much more severe problem in rotary engines than it is in your standard combustion engine. Carbon build-up on the piston surface can cause pre-ignition, which damages your engine over time — and not a long period of time, either. Pre-ignition is also a major reason why you can’t use a lower octane rating of gas than your vehicle requires. The best solution is to tune and run your vehicle with E85 fuel inside of standard gasoline.

Pitting is another issue that can damage rotary engines

Rotary engines feature a ‘piston’ which is forged from cast iron and shaped like a rounded triangle — which is where the Dorito jokes of the rotary engine come from. This piston, rather than moving up and down within a cylindrical housing, spins around a chamber, creating separate compartments in which the standard internal combustion process happens: intake, compression, combustion, and exhaust. Pitting on the rotary surface can be caused by damaged apex seals and pre-ignition. The best way to protect the engine’s internal components is to pre-mix fuel, as explained by Rob Dahm in the video down below.

Among the throwback vehicles made popular by the Fast and Furious franchise, we have heard some rumors of a potential RX comeback with a new rotary engine, but these claims have yet to be substantiated by Mazda.

Blown apex seals are a rotary-exclusive problem

If you’ve ever met someone who owns a rotary vehicle, chances are they will tell you about their apex seals. Really, the problem with blown apex seals seems to be unavoidable, and it’s an issue almost every RX-7 and RX-8 engine has or will face. This is the most common failure owners experience, and it can oftentimes be frustrating as it is prone to happen many times. The only way to resolve this issue is to invest in some hardier, more durable apex seals, which may or may not resolve the problem entirely, but can give you more time in between changes.

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