REDS 321 ESTREMO X Line Off-Road Buggy Engine

REDS 321 ESTREMO X Line Off-Road Buggy Engine

ENBU0042 REDS 321 ESTREMO X Line Off-Road Buggy Engine

Reds Racing is enthusiastic to introduce an important evolution within its high-end off-road nitro engine lineup.

As part of this development, Reds Racing unveils a brand-new engine family called the X Line, which will run alongside the current flagship 721 Superveloce Gen5 – S Line Version 2026.

The new X Line debuts with the 321 ESTREMO™, a 3-port engine designed to offer a different driving character compared to the well-known 721 S Line platform.

The 721 S Line will continue to be fully produced in Italy, maintaining the same philosophy, engineering approach, and performance characteristics that have defined it over the years.

The new 321 engine is manufactured in Japan and has been fully developed according to Reds Racing design, engineering, and testing specifications. Final assembly and tuning are carried out directly by Mario Rossi and Marco Rossi, ensuring the performance standards and precision expected from Reds Racing engines.

The development of the new 321 ESTREMO™ represents an important collaboration between REDS Racing and one of the most respected companies in the RC engine industry, O.S. Engines.

REDS Racing was founded by Mario Rossi, one of the most influential figures in RC engine history and co-founder of the legendary Novarossi brand since 1984. His decades of experience in high-performance racing engine design have helped shape some of the most successful engines ever produced.

By combining REDS Racing’s Italian racing engineering and development philosophy with the manufacturing expertise and precision of Japanese engineering, this project brings together the best of two worlds.

The result of this collaboration is a new engine platform designed to deliver outstanding performance, reliability, and drivability—an engine that represents the perfect blend of Italian racing passion and Japanese manufacturing excellence.

From a technical standpoint, the 321 features a 3-port configuration designed to deliver increased torque, resulting in a driving feel that differs significantly from the current 721 platform.

The cylinder and sleeve design has been developed starting from the classic Japanese 3-port architecture, well known for its simplicity, reliability, and strong torque characteristics. Reds Racing engineers further refined this concept by introducing additional internal flow channels designed to guide and optimize the air-fuel mixture movement inside the cylinder.

These channels improve cylinder filling efficiency, enhancing the combustion process and increasing overall performance.

The cylinder is paired with an ultra-lightweight piston, specifically designed to reduce reciprocating mass. By minimizing the moving masses inside the engine, Reds Racing engineers were able to further improve engine responsiveness and maximize overall power output.

The result is a design that maintains the simplicity and drivability of a traditional 3-port engine, while incorporating advanced details that improve internal fluid dynamics and overall engine efficiency.

REDS Racing engineers also dedicated extensive development work to the combustion chamber design to guarantee consistent performance with different racing fuels.

Two dedicated combustion chamber configurations have been developed, allowing the engine to perform optimally with both 25–30% nitro fuel and 16% nitro fuel.

Each combustion chamber has been specifically designed to perfectly match the characteristics of its respective fuel blend, ensuring the best balance of performance, reliability, and fuel efficiency under a wide range of racing conditions.

Another key innovation featured on the new 321 engine is the REDS Racing AirBoost™ backplate, a true concentration of technology designed to further enhance engine performance and efficiency.

The AirBoost™ backplate has been engineered to increase mid-to-high RPM power, improve fuel efficiency, and provide a faster return to idle.

Its internal design features two dedicated channels that direct the air-fuel mixture toward the rear section of the transfer ports, creating a supercharging effect that improves cylinder filling and significantly enhances engine power.

In addition, the AirBoost backplate is coated with a DLC (Diamond-Like Carbon) treatment, which reduces sliding friction between the connecting rod and the backplate. This advanced coating improves engine efficiency, reduces wear, and contributes to lower fuel consumption.

To guarantee extremely easy tuning and consistent performance on every track, the 321 ESTREMO features a carburetor based on the legendary O.S. Speed 21J, one of the most reliable and widely used carburetors in the RC racing world.

REDS Racing engineers selected the proven 21J platform and further enhanced it with the Venturi XFlow™ system, designed to maximize airflow and improve carburetion stability.

Thanks to its Ultra Short design, the Venturi XFlow™ optimizes the air intake path and allows the engine to breathe more efficiently. This results in faster throttle response, easier carburetor tuning, and stronger overall engine performance.

The Venturi XFlow™ is available in three sizes to adapt the engine to different track conditions and racing preferences:

• 6 mm – Maximum torque and improved fuel efficiency
• 7 mm – Perfect balance between power and drivability
• 8 mm – Maximum airflow and top-end performance

This system ensures stable carburetion and precise throttle response, giving drivers the confidence needed to push the engine to its limits in any racing condition.

The REDS ultra-lightweight cooling head has been engineered to maximize heat dissipation while minimizing overall engine weight.

Its optimized fin structure improves cooling efficiency and helps maintain stable engine temperatures even during demanding racing conditions, ensuring consistent performance during long finals and intense competition.

Technical Specification: