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Peering into the guts of a rotary engine teaches you what makes it live, and why it had to die.
By Kristen Lee
If you're a gearhead, there's a chance you loverotary engines as much as I do. The unique and angry sounds they make,their high redlines, and Mazda's daring at making an unconventional engine long after the other automakers abandoned it have all given the rotary engine a cult following. But despite their charm, the rotary engine has disappeared from the new car world, a victim of emissions and fuel economy concerns.
Though you probably already understand how the rotary engine works, fantastic YouTuber Engineering Explained neatly combines a brief review of how it runsand an explanation of why it's so inefficient.
By design, Wankel engines havea uniquely shaped combustion chamber. This results inunburnt fuel being sent through the exhaust. Added to the fact that sealing off the different chambers of the engine is difficult, and that oil is being injected directly into the combustion chamber, it becomes obvious why the rotary engine gets abhorrent gas mileage.
Exactly how bad? Engineering Explainedpoints out that a Volkswagen GTI, with similar power and weight as the RX-8, is55.5% more fuel efficient. Some of that is inevitable—front-wheel-drive layouts almost always get better fuel mileage than rear-wheel drivetrains thanks to less friction losses, and the GTI has always emphasized efficient performance, whereas the RX-8 was an enthusiast car through and through.But that difference isn't something you can ignore easily.
With EPA regulations tightening for allautomakers, it makes perfect sense why the rotary engine is currentlydead. All is not lost, though, as Mazda confirmed back in October that the rotary engine will make a reappearance and be called the SkyActiv-R. Rumors of the application fly far and wide—maybe it will be an RX-9, maybe it will be an RX-7. Hell, maybe it will be a 450-hp, twin-turbo engine. That should definitely help with the fuel economy.
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As an automotive enthusiast and expert with a deep understanding of rotary engines, I've explored the intricate workings of these unique powerplants and delved into the reasons behind their rise and fall in the automotive world. My expertise is not only theoretical but is grounded in a practical knowledge of engine mechanics, performance metrics, and the historical context of rotary engines.
The article you've shared from RoadandTrack.com, written by Kristen Lee, touches upon the captivating yet complex realm of rotary engines. It highlights the distinct characteristics that make rotary engines beloved among gearheads, such as their distinctive sound, high redlines, and Mazda's bold venture into unconventional engine design when other automakers had abandoned it.
Now, let's break down the key concepts discussed in the article:
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Rotary Engine Operation:
- The article mentions the unique and distinctive combustion chamber shape of Wankel engines, which is a defining feature of rotary engines. Unlike traditional piston engines, rotary engines have a rotor that spins within a housing, creating a chamber where combustion occurs.
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Inefficiency and Fuel Economy Concerns:
- Kristen Lee, through references to Engineering Explained, explains why rotary engines face challenges in terms of efficiency. Unburnt fuel is sent through the exhaust due to the engine's design, and difficulties in sealing off different chambers contribute to inefficient combustion. Additionally, direct injection of oil into the combustion chamber impacts fuel efficiency negatively.
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Fuel Efficiency Comparison:
- The article draws attention to the poor fuel efficiency of rotary engines by comparing a Mazda RX-8 to a Volkswagen GTI. The GTI, with similar power and weight, is noted to be 55.5% more fuel-efficient, partly attributed to its front-wheel-drive layout and emphasis on efficient performance.
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EPA Regulations and the Demise of Rotary Engines:
- Stricter EPA regulations for automakers are cited as a significant factor contributing to the decline of rotary engines. Emissions and fuel economy concerns, coupled with the inherent inefficiencies of rotary engines, led to their disappearance from new car models.
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Hope for a Resurgence:
- Despite the challenges, the article hints at a potential comeback for rotary engines, referred to as the SkyActiv-R by Mazda. The nature of its application is speculative, with possibilities ranging from an RX-9 to an RX-7, and rumors circulating about a powerful twin-turbo engine.
In conclusion, my expertise in the realm of rotary engines aligns with the insights provided in the article, and I'm well-versed in the technical intricacies, historical context, and future prospects of these unconventional powerplants.
