New 321 ESTREMO™ X Line Off-Road 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.

A Collaboration Between Two Icons of RC Engine Technology

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.

Advanced 3-Port Engine Design

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.

Optimized Combustion Chambers

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.

AirBoost™ Backplate

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.

Easy to Tune, Built to Win – 21J with Venturi XFlow™

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.

REDS Ultra-Lightweight Cooling Head

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.

Extreme Durability and Precision Engineering

The new engine integrates several advanced durability improvements designed to maximize performance and reliability.

Both the crankshaft and the backplate feature DLC (Diamond-Like Carbon) coating, a technology known for its exceptional hardness and extremely low friction coefficient.

Thanks to this advanced treatment, the crankshaft durability can increase by up to three times compared to a conventional steel crankshaft, while also reducing internal engine friction.

The reduced friction between the connecting rod and backplate also helps extend conrod life by approximately 50%, improving long-term reliability during demanding racing conditions.

The crankshaft features a double-balanced design, while its internal geometry has been revised to improve both power characteristics and engine smoothness.

The engine crankcase has been manufactured according to the highest quality standards, ensuring excellent rigidity, perfect component alignment, and maximum durability.

Key Technical Features

• 3-port engine design focused on high torque output

• Advanced cylinder and sleeve design with optimized internal flow channels

• Ultra-lightweight piston to reduce reciprocating mass

• REDS ultra-lightweight high-efficiency cooling head

• AirBoost DLC-coated backplate for improved power and efficiency

• DLC-coated crankshaft with double balancing

• Carburetor based on O.S. Speed 21J design

• Venturi XFlow™ intake system available in 6, 7, and 8 mm sizes

• Two dedicated combustion chambers for 16% and 25–30% nitro fuels

Two Engines, Two Racing Philosophies

With the introduction of the 321 ESTREMO, Reds Racing now offers two distinct engine platforms designed to suit different track conditions and driving styles.

REDS 721 Superveloce

• 7-port engine architecture

• Exceptional top-end speed

• Outstanding fuel efficiency

• Extremely smooth and linear power delivery

• Ideal for high-speed tracks and European-style layouts

  
  

REDS 321 ESTREMO

• 3-port engine architecture

• Strong bottom-end torque and acceleration

• Excellent throttle response and drivability

• Designed for technical tracks with big jumps

• Ideal for American-style layouts and demanding off-road conditions

  
  

Together, the 721 Superveloce and the 321 ESTREMO give racers the possibility to choose the engine that best matches their track conditions, driving style, and racing strategy.

With the introduction of the X Line, Reds Racing expands its presence in the off-road racing segment, offering drivers a new engine platform designed to deliver a different performance philosophy alongside the established 721 S Line.

The 321 ESTREMO represents the perfect fusion of Italian racing engineering and Japanese manufacturing precision, setting a new benchmark for performance, drivability, and reliability in the world of off-road RC racing engines.

Technical Specifications

- Category: 1/8 Buggy and Truggy

- Displacement: 3.5 cm³

- Bore: 16.4 mm

- Stroke: 16.4 mm

- Inlet Ports: 3- Outlet Ports: 1

- Front Bearing: 7×19×6 with single high-performance seal

- Rear Bearing: 14×25.4×6 – 9 balls high-durability ceramic bearing

- Carburetor Type: VLX3-A aluminum long needle

- Venturi Diameter: 7.0 mm (optional venturi sizes: 6.0 mm and 8.0 mm – carburetor body 9.0 mm)

- Backplate: AirBoost DLC-coated backplate

- Crankshaft: DLC-coated with two tungsten balancing weights

- Weight: 345 g

Recommended Accessories

To maximize the performance of your 321 Estremo™ engine, Reds Racing recommends pairing it with the following components:

- Glow Plug: REDS TS3 or TS4

- Exhaust System: 2143 X-ONE X Line

- Clutch System: REDS TETRA-X Clutch System

- Fuel: 16–30% nitro with 8–10% oil

- Break-In Fuel: 12% oil

Not compatible with S Line Exhausts, manifolds, gaskets, piston/sleeve/conrod set and spring set.

Available Versions:

ENBU0042 321 ESTREMO 16% NITRO - X Line

ENBU0042B 321 ESTREMO 16% NITRO - X Line - Pre break-in service by Mario Rossi

ENBU0044 321 ESTREMO 25-30% NITRO - X Line

ENBU0044B 321 ESTREMO 25-30% NITRO - X Line - Pre break-in service by Mario Rossi.

COBU0036 COMBO 321 ESTREMO 16% NITRO with 2143 TORQUE XONE - X Line

COBU0036B COMBO 321 ESTREMO 16% NITRO - X Line - Pre break-in service by Mario Rossi

COBU0037 COMBO 321 ESTREMO 25-30% NITRO with 2143 TORQUE XONE - X Line

COBU0037B COMBO 321 ESTREMO 25-30% NITRO - X Line - Pre break-in service by Mario Rossi