Electric and nitro: two kinds of car, two sets of rules.

Two sections, two rule sets

Wikipedia describes electric cars as having motor power regulated by an electronic speed controller, and nitro cars as carrying a small combustion engine. The world body, IFMAR, mirrors that split in its structure: it has an IC (internal combustion) section and an Electric section, each with a chairman, and separate World Championship rule books for each (IFMAR 1/8 IC off-road rules 2024, 3.1.a; IFMAR electric off-road rules 2019, 4.2.11). EFRA likewise runs IC Track, 1/8 Buggy and Large Scale sections alongside its Electric sections.

Each section below gives one body's rule from one edition. Electric and nitro classes have separate rule books, and neither body's limits apply at the other's events.

Electric: battery and motor limits

Batteries

EFRA's Handbook 2026 (Appendix 3, version 4, A.3.1 to 3.3) sets each electric class's battery limit: lithium-based packs (LiPo or LiFe) at no more than 3.8 V nominal for 1/12, and no more than 7.6 V (LiPo) or 6.6 V (LiFe) nominal for 1/10 touring, front-wheel drive, Formula One and off-road. EFRA's Appendix 4 says that from 2009 EFRA homologates only lithium-based batteries. IFMAR's Electric Racing Batteries and Motors document (March 2023) likewise approves only lithium-based batteries. For IFMAR's electric GT class, the 2025 GT and GTE rules allow at most 4S LiPo, in one pack or two equal packs, in a mandatory hard case, at no more than 16.80 V at the start of a race, and penalise over-voltage.

EFRA also requires LiPo and LiFe drive batteries to sit in a "LiPo sack" whenever they are charged or discharged, outside a race (A.3.4). EFRA defines the sack as a receptacle designed for charging and built to contain a LiPo or LiFe fire, and penalises breaches. That is EFRA's requirement and EFRA's definition; this site does not describe any sack or case as preventing a fire. The full battery rules, body by body, are on battery rules by body.

Motors

Since May 2016, only motors on EFRA's homologation lists may be used at EFRA European Championship and Grand Prix events in the electric classes (Appendix 3, A.2 and A.7.1.1), while Appendix 4, section 5, says homologated 05 motors are required from 1 June 2016. EFRA moved its rules on 05-size brushless motors and lithium batteries into Appendix 4 from 2018. Its classes are either Modified or Spec: a Spec class fixes the motor's turns (13.5T or 21.5T in the European Championship list) and requires a "blinky" speed controller, which EFRA defines as running a zero-timing profile that leaves the motor's preset timing alone and disables boost, shown by a blinking light when armed (A.4.3.1). Motor rules in detail are on motors and speed controllers.

Nitro: engine, fuel and noise limits

Engines

IFMAR sets engine capacity by class:

• 1/8 IC off-road (2024, 2.2): at most 3.5 cc (0.214 cu in), no tolerance; fuel tank, filter and lines to the carburettor at most 125 ml. Cars need brakes and a clutch so the car can be held still with the engine running.
• 1/8 IC track (2023, 5.1 to 5.4): at most 3.5 cc, no tolerance; tank at most 125.00 ml.
• 1/10 IC track (2024, 5.8 to 5.11): at most 2.11 cc (.12), air-cooled, front rotary valve two-stroke, glow plug ignition only, no forced induction, carburettor at most 5.50 mm; tank 75.00 cc.
• 1/8 GT (2025): 3.5 cc (.21) engines, tank at most 150 cc, with no refuelling during a 7-minute heat.

Fuel composition

IFMAR's 1/8 IC rules (off-road 2024, 2.7; track 2023, 5.23) allow fuel made only of methanol and/or ethanol, lubricating oil, a small amount of anti-corrosion chemicals and at most 25% nitromethane by volume, with a specific gravity no heavier than 0.91 g/cc at 20 C. Hydrazine, hydrogen peroxide, toluene and propylene oxide are named as prohibited. IFMAR's 1/10 IC track rules (2024, 5.22.1) and its 1/8 GT rules (2025, 4.2) allow the same ingredients but at most 16% nitromethane by volume and a specific gravity of no more than 0.87 g/cc. Those are different IFMAR limits for different classes.

EFRA's position on 1/8 off-road fuel is unconfirmed: a search summary of its 2023 section minutes says a proposal was made to use only "16% EU" fuel at all European Championships, and whether it was adopted was not found.

Separately from any racing rule, EU law restricts nitromethane sold to the public. Estonia's Ministry of Economic Affairs (page updated 28 August 2023) says that under Regulation (EU) 2019/1148, applicable from 1 February 2021, nitromethane above 16% by weight is restricted for private individuals. Red RC, a trade publication, reported on 5 October 2023 that the change cut the permitted figure for modellers from 25% to 12%; that 12% figure was not found in any regulator's text. Both versions are given, and neither is confirmed against the regulation's annex. IFMAR's limits are by volume and the EU threshold is by weight, so the numbers are not directly comparable. More is on nitro fuel rules, and what NIOSH and the HSE publish about methanol and nitromethane is on fuel hazards.

Noise

IFMAR's 1/10 IC track rules (2024, 5.8) require homologated double-chamber mufflers and a homologated inlet silencer box; to be homologated, a muffler may not exceed 85 dB measured at 10 m and 1 m height with the engine at 40,000 rpm. IFMAR's 1/8 IC off-road rules (2024, 2.3) allow only IFMAR-homologated silencers. EFRA's Handbook 2026 Appendix 8 registers mufflers rather than homologating them, and its sections measure noise at events with what EFRA calls a "Noise Trap". No regulator noise rule specific to RC tracks was found. See noise and mufflers.

Petrol: large scale

Large-scale cars can run petrol engines. The BRCA's Large Scale Off Road national series (section page, 2026) runs 2WD buggy, 4WD buggy, short course and open classes with petrol engines of 23, 26, 30 or 32 cc. The BRCA's 2026 section rule book itself was not read.

Hazards

Lithium batteries and nitro fuel both carry hazards that regulators and fire services have published on; those are on battery fire risk and fuel hazards. A battery fire, swallowed or splashed fuel, or an injury needs the emergency services or medical care.