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The smallest Wankel engine in the available documentation is a 0.137 cc project described by NITTO MFG., LTD.—but Nitto does not publish its power, weight or dimensions. The clearest documented example of a small rotary engine’s output is a separate 19.75 cc RC airplane engine, listed by Nitto at approximately 1.8 hp. Those are different engines, and the published figures do not establish that the 0.137 cc project delivers a particular power-to-weight advantage.
What is the 0.137 cc Wankel engine?
NITTO MFG., LTD. says a university in the United States commissioned it in 2000 to design and manufacture an ultra-miniature Wankel-type rotary engine with a displacement of 0.137 cc. Nitto’s project description provides the displacement, but no output, weight, dimensions or present retail availability. Nitto’s project page calls the client “a certain university”; Berkeley appears in the company page’s heading, so that attribution is the company’s identification rather than independent confirmation.
Displacement alone cannot tell you how powerful or light an engine is. Without power and weight figures for this specific project, its power-to-weight ratio cannot be calculated or compared reliably.
What published figures do other small Wankel engines have?
These examples show why it matters to distinguish a miniature project from model engines with published performance specifications. The figures below are manufacturer listings, not independent test results.
#1 Best Overall
- Experience the unique engineering of the Wankel engine with the Mould King 10212. This model meticulously replicates the triangular rotor's eccentric orbital motion, showcasing the intake, compression, ignition, and exhaust cycles. It provides a fascinating, high-fidelity look into one of the most innovative internal combustion designs in automotive history.
- Equipped with a dedicated power module, this 1130-piece model transitions from a static build to a fully operational mechanical marvel. The integrated motor drives the internal rotor and synchronization gears, allowing you to observe the continuous, smooth rotational power delivery that defines the rotary engine's legacy.
- With over 1130 precision-engineered components, this kit offers a deep dive into advanced structural design. Every piece is crafted for a high-tolerance fit, ensuring the complex internal gear system and the unique epitrochoid housing function with seamless mechanical accuracy, reflecting premium manufacturing standards.
- Designed with a sleek, technical aesthetic, this engine model transcends traditional building sets. Mounted on a stable base, it serves as a premier centerpiece for executive offices, design studios, or home galleries. Its intricate exposed-gear look makes it an essential acquisition for any serious mechanical or automotive collection.
- Engineered for those who seek a focused and cognitively engaging construction experience. The assembly process provides a comprehensive understanding of rotational kinematics and engineering physics. Accompanied by a professional-grade manual, this project offers a rewarding challenge for enthusiasts of complex machinery and industrial architecture.
| Engine | Displacement | Published performance and weight | Application and qualifications |
|---|---|---|---|
| Nitto ultra-miniature project | 0.137 cc | Output and weight not stated by Nitto’s project page | Commissioned in 2000; current sale is not established. |
| Nitto NRG-20EP | 19.75 cc | Approximately 1.8 hp; 1,800 g including mount; practical operating range 2,000–10,000 rpm | RC airplane engine; mixed gasoline. Silencer and ignition battery are excluded. Nitto product listings |
| Nitto NRG-20EH | 19.75 cc | Horsepower not stated; 1,800 g including mount and cooling fan; practical operating range 2,400–11,000 rpm | RC helicopter engine; mixed gasoline. Silencer and ignition battery are excluded. Nitto product listings |
| TOYAN RS-L200 | 2.6 cc per rotor × 2 | 1.46 PS at 18,000 rpm; 415 g engine weight | Water-cooled twin-rotor model engine; starting accessories are separate. TOYAN’s listing |
| Wankel SuperTec KKM350 series | 350 cc per rotor | Industrial output figures vary by model and fuel | Industrial engines for uses including generators and range extenders, not miniature model engines. Wankel SuperTec overview |
The clearest small-engine power example
Nitto lists its NRG-20EP at approximately 1.8 hp, 19.75 cc and 1,800 g including its mount, with a practical operating range of 2,000–10,000 rpm. It is intended for RC airplanes, runs on mixed gasoline and does not include a silencer or ignition battery. The 19.75 cc displacement is roughly 144 times the 0.137 cc project’s displacement; the NRG-20EP’s power specification must not be assigned to the miniature project.
A twin-rotor model with a different specification basis
TOYAN lists the RS-L200 at 2.6 cc per rotor, 1.46 PS at 18,000 rpm and 415 g engine weight. Its listing describes a water-cooled model and excludes starting accessories. TOYAN warns that it is not a simple toy and requires technical, hands-on ability. The 415 g figure is labeled engine weight, unlike Nitto’s NRG-20EP figure, which includes the mount, so the weights are not directly like-for-like.
Rank #2
- ✨The authentic engine model based on the rotary engine is able to directly transform the combustion expansion force of combustible gas into driving torque.
- ✨The Wankel engine consists of a rotor in the shape of a Leroy triangle in an oval space and three independent combustion chambers divided by three faces of the rotor in the oval space. Due to the eccentric operation of the rotor, the volume will constantly change to achieve the intake, compression, ignition and exhaust process required by the four-stroke operation.
- ✨Designed with the highest precision to further walk through the principle of the rotor engine for impressive fun.
- ✨Build your own rotor engine model in your living room according to the detailed assembly procedure manual to show your engineering talents. Packed in a luxury exquisite gift box, the model is perfect for personal use or as an incredible gift to others.
- ✨Do not play with the assembled toy violently to avoid damage to the model. Please keep it properly after use and pay attention to cleaning and maintenance for durability.
Can you buy the 0.137 cc engine?
Nitto’s project page documents a commissioned design-and-manufacture project, not a retail product listing; it does not establish that the 0.137 cc engine is available to buy. A separate product to consider as a hands-on rotary model is the TOYAN RS-L200 twin-rotor rotary engine model. It is not the Nitto project, and its listing says starting accessories are separate.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Where does the discontinued Graupner RE38 fit?
Nitto says it manufactured the Graupner Best.-Nr.1880, or RE38, released in 1993 with a displacement of 37.41 cc, and that production was later discontinued. In its historical account, Nitto describes its own tests as identifying areas for improvement, including idling and durability, and says it later redesigned its NR series with features such as a two-part apex seal intended to improve airtightness. Those assessments are the manufacturer’s account, not an independent comparison. Nitto’s rotary-engine information
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Quick Recap
Best Value
- Custom Made by : Rotary13B1
- Size: 12.75in x 12in x 3in
- Design is doubled sided, reverse side is printed as well.
- Color as shown with black coolant passage details.
Rank #4
- 🛠️ Authentic Wankel Rotary Mechanics - This detailed model directly replicates the rotary engine cycle: a Reuleaux triangle rotor spins inside an oval housing, creating three separate combustion chambers. Watch as the eccentric motion continuously changes volume to perform the four‑stroke intake, compression, ignition, and exhaust processes just like the real engin
- 🔍 Functional Dynamic Display - Once assembled, the model visibly transforms the expansion force of combustible gas into rotational torque. The open structure lets you see every stage of the rotary cycle in motion, turning an abstract internal combustion concept into a captivating, hands‑on demonstration for students and enthusiasts
- 🎨 Hybrid Metal & ABS Construction - Built from a combination of durable metal components and high‑grade ABS parts, the model offers a realistic weight and feel. Advanced precision manufacturing ensures tight fits and smooth operation, resulting in a striking desktop piece that showcases the elegance of Wankel engineering
- 📖 DIY Assembly with Detailed Manual - Build your own rotary engine in around two to three hours using the comprehensive step‑by‑step illustrated instructions. All parts are included—just bring your curiosity. A rewarding project that lets you display your engineering talent and proudly exhibit the finished model
- 🎁 Luxury Gift Box & Care Tips - Delivered in an exquisite gift box, this model is perfect for personal use or as an unforgettable present for birthdays and holidays. Handle it with care, avoid rough play, and clean gently with a dry cloth. Store in a cool, dry place to maintain its beauty and functionality
Rank #3
- ✨The authentic engine model based on the rotary engine is able to directly transform the combustion expansion force of combustible gas into driving torque.
- ✨The Wankel engine consists of a rotor in the shape of a Leroy triangle in an oval space and three independent combustion chambers divided by three faces of the rotor in the oval space. Due to the eccentric operation of the rotor, the volume will constantly change to achieve the intake, compression, ignition and exhaust process required by the four-stroke operation.
- ✨Designed with the highest precision to further walk through the principle of the rotor engine for impressive fun.
- ✨Build your own rotor engine model in your living room according to the detailed assembly procedure manual to show your engineering talents. Packed in a luxury exquisite gift box, the model is perfect for personal use or as an incredible gift to others.
- ✨Do not play with the assembled toy violently to avoid damage to the model. Please keep it properly after use and pay attention to cleaning and maintenance for durability.
What the available numbers do—and do not—show
- The 0.137 cc figure establishes the miniature project’s displacement, not its power or power-to-weight ratio.
- The NRG-20EP and TOYAN RS-L200 have published performance figures, but each belongs to a different engine with a different application and specification basis.
- The NRG-20EH has listed weight and operating range but no horsepower figure on Nitto’s product information.
- The KKM350 series provides industrial scale context; it is not a miniature engine comparison.
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