Nitro engines and mufflers: the limits the rule books set.

What the rules regulate

IFMAR's IC (internal combustion) section writes separate World Championship books for 1/8 off-road, 1/8 track, 1/10 track and 1/8 GT. Each limits the engine's capacity and fuel system, and requires homologated mufflers and inlet silencers. EFRA's IC engine appendices for 1/8 track, 1/8 off-road and 1/10 track were not read for this site, so EFRA engine limits are not given; its muffler rules (Appendix 8) were read and are below. ROAR's current rule book and the BRCA's 2026 section rules were not read either.

Engine and fuel-system limits (IFMAR)

All three of the 1/8 and 1/10 books read say cars are impounded at the end of the finals and may be inspected for engine size and fuel tank capacity. The limits on what the fuel itself may contain are on nitro fuel rules.

Mufflers and inlet silencers (IFMAR)

IFMAR uses two pieces of homologated equipment for noise: the muffler on the exhaust, and an inlet noise silencer (INS) box on the engine's inlet.

• 1/8 IC track (2023, 5.7): homologated mufflers with at least three chambers and a straight circular outlet, and homologated INS boxes, are mandatory. The maximum noise for a muffler with its INS box is 85 dB measured at 10 m distance and 1 m height, and IFMAR's own noise definition is final. The outlet must point horizontally or downward, and mufflers may be cut open for checks.
• 1/10 IC track (2024): homologated double-chamber mufflers with homologated INS boxes. For homologation each muffler is tested on an engine at 40,000 rpm and may not exceed 85 dB at 10 m and 1 m height. The tailpipe's internal diameter is at most 5.20 mm, with a minimum length of 10.00 mm.
• 1/8 IC off-road (2024, 2.3): only IFMAR-homologated silencers, carrying their homologation number. ROAR, EFRA, FEMCA or FAMAR may homologate a silencer up to four months before the event, and IFMAR publishes its Approved Muffler List two months before.

Mufflers at EFRA events (EFRA Handbook 2026, Appendix 8)

EFRA requires every engine to have an exhaust system and an inlet silencer to reduce noise. It now speaks of "registration" rather than homologation of mufflers, and says it made that change so that a listed muffler is not taken as always acceptable. Its rules in summary:

Appendix 8 also states that the legal noise level within the European Community is 83 dB without the need for extra personal protection. That is EFRA's statement about the law; the EU legislation behind it was not read for this site, so the figure is unconfirmed as law. No regulator's noise rule specific to RC tracks was found. More on noise and mufflers.

EFRA's 2024 General Rules (the latest edition read) add two engine points: referees watch for cars exceeding the noise rules through a lost or damaged silencer (7.1.12), and a plastic or wooden baton is mandatory at marshal posts at IC events as an aid to stop a running engine (8.15).

Large-scale petrol engines (BRCA)

The BRCA's large-scale off-road series uses petrol engines rather than glow engines. Its Large Scale Off Road section page (2026) lists engines of 23, 26, 30 or 32 cc for its national series. The briefing for one round of that series (October 2025) says random scrutineering included sound-level checks; whether that is a handbook-wide BRCA rule was not confirmed.

Fuel hazards and emergencies

Two chemicals in nitro fuel, methanol and nitromethane, are classed by NIOSH as flammable liquids, and NIOSH lists eye irritation, visual disturbance and optic nerve damage among methanol's symptoms. This site gives no starting, running or tuning procedures; the makers' instructions, the class rule book and the track's safety rules govern those. What regulators publish about methanol and nitromethane is on fuel hazards. A burn, a fuel exposure or a fire needs the emergency services or medical care.