Parts/Engines & fuel/Nitro & glow engines/Ruddog RNX.4 3.5cc (.21) Competition Off-Road Nitro Engine (25% Nitro Version) w/Storage Bag
Ruddog RNX.4 3.5cc (.21) Competition Off-Road Nitro Engine (25% Nitro Version) w/Storage Bag
Ruddog

Ruddog RNX.4 3.5cc (.21) Competition Off-Road Nitro Engine (25% Nitro Version) w/Storage Bag

Part # RDGRP-0822-25
Where to buy
$440.79
AMain Hobbies
Seen Oct 12, 2026
$440.79Buy
Prices are as last seen at the store; stock is not tracked.

About this part

Nitro Engine Overview:

Unleash elite-level performance with the Ruddog Racing RNX.4, tested on the world stage and built for serious 1/8 off-road competitors who demand power, efficiency, and reliability in every lap.

About the RNX.4 Nitro Engine


World-Class Racing Proven

The Ruddog Racing RNX.4 builds on the legacy of the RNX22.3, refined with real-world feedback and tested at the 2024 World Championships by Marcus Kaerup. This engine delivers explosive power, advanced drivability, and rock-solid reliability, perfect for serious 1/8 off-road buggy and truggy racers. Whether you're chasing podiums or tuning for performance, the RNX.4 is engineered to compete at the highest level.

Precision Engineered Performance

Featuring a DLC-coated crankshaft and optimized engine head for 25–30% nitro fuel, the RNX.4 ensures enhanced fuel flow, extended runtime, and a smooth, responsive power band. Revolution Design’s Ultra Backplate and Carburetor Dust Cover Seal further boost fuel efficiency and engine protection, keeping the internals cleaner and more consistent under harsh racing conditions.

Durability Meets Efficiency

Built for endurance, the RNX.4 incorporates performance ball bearings, precision-machined internals, and an advanced cooling system for peak performance in demanding conditions. Packaged in a premium Ruddog engine bag, this engine combines cutting-edge tech, professional-grade durability, and race-ready efficiency, making it an essential upgrade for competitive racers.

Features:

  • Based on the proven RNX22.3 platform
  • Tested at the 2024 World Championships
  • DLC-coated crankshaft improves durability
  • Engine head optimized for 25–30% nitro
  • Ultra Backplate increases fuel efficiency
  • Carburetor seal protects against dust
  • Delivers strong power and control
  • Includes a high-quality engine storage bag

Includes:

  • (1) RNX.4 3.5cc (.21) Competition Off-Road Nitro Engine (25% Nitro Version)
  • (1) Storage Bag

Specifications:

Displacement .21 cu.in (3.5cc)
Recommended Application 1/8 Off-Road
Bore -
Stroke -
Output -
Intake Ports -
Exhaust Ports 1
Practical RPM -
Weight -
CA Residents Prop 65 Warning WARNING: This product can expose you to chemicals including Di(2-ethylhexyl)phthalate (DEHP), which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov Details...

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