Speed controllers: what the rule books allow an ESC to do.

What the part is

Wikipedia describes electric RC cars as cars whose motor power is regulated by an electronic speed controller, in contrast to nitro cars with a combustion engine. The racing rules treat the ESC as one of a small number of devices a car may carry, and they limit what it may do, most of all in classes that run a Spec motor. Makers' descriptions of their own controllers are claims, and this site does not compare or test them.

EFRA (EFRA Handbook 2026, Appendix 3)

What an ESC may contain

• A 12.7: any ESC may be used if it does not interfere with lap counting, computers or transmitters, but it must sit inside the car and not protrude through the body shell.
• A 4.3: an ESC may include a current or voltage limiter (EFRA names a timed delay, a current limiter and programs as examples) and a passive data recorder, but these may be set only while the car is stationary.
• A 4.1 and 4.2: the receiver may operate steering and motor management; using it to capture signals from sensors in the car is banned. Automated steering, gyroscopes controlling the car's movement, traction control and active suspension are not allowed.
• A 4.4: no signals other than those of the official lap-counting transponder may be sent from the car.

The zero-timing profile, or "blinky"

At events for Spec-class brushless motors, EFRA's rule A 4.3.1 allows only an ESC running what it calls a "zero timing profile". As the rule defines it, such an ESC:

• must not alter the motor's preset mechanical timing;
• must disable advanced functions, which the rule lists as boost, "cheat mode" and turbo;
• must use 6-step commutation that follows the motor's hall sensors one to one;
• shows a blinking LED when armed in neutral, which is where the informal name "blinky" comes from.

EFRA calls this profile "Boost 0". In its GT12 rules (C 4.1), EFRA says a zero-timing ESC must have any timing-advance feature disabled and be set to an approved mode, which it names as the "ROAR blinking LEDs mode", and only ESCs on EFRA's Approved Blinky ESC list may be used. GT12 also bans the reverse function (C 4.2).

Besides GT12, the EFRA 2026 classes that name a blinky ESC are 1/12 Modified, 1/12 Spec 13.5T, the 1/12 17.5T class and 1/10 touring car FWD (Appendix 3, A 7.1.1 and B 6). The motors for each class are on motors.

IFMAR

• Electric Off Road rules (13 November 2019), 4.5: any type of mechanical or electronic speed controller may be used. The receiver may have only two devices connected, normally the steering servo and the ESC, plus an optional separate battery. Traction control, active suspension, gyroscopic steering control, sensors measuring suspension, wheel speed or tyre slip, and active telemetry are not allowed.
• Electric Off Road rules (2019), 4.2: a car may have at most two control devices: two servos, or a servo and a speed control.
• Batteries and Motors (March 2023), 5: a speed control compatible with sensored motors uses the six-position JST header named in the rule, with power connectors marked A, B and C.

IFMAR's Spec motor rules, and how its Spec wind list differs from EFRA's, are summarised on the motors page.

ROAR

ROAR's current rule book was not read for this site. Its rule book update of 18 October 2024 records three ESC rules:

• Rule 7.3.6: ESC firmware must be the most recent ROAR-approved version; beta software is prohibited, and any software change must be re-inspected and approved by ROAR.
• Rule 11.3.5.2: the ban on dynamic timing changes applies only in "blinky" mode.
• Rule 11.3.4.3: in blinky mode, timing-mode changes may be made only with an external setup box or wireless module, not from the transmitter or the ESC's own buttons.

EFRA's GT12 rule cites ROAR's mode by name, which is the clearest link found between the two bodies' ESC rules. Whether ROAR's current rule book adds further ESC limits is unconfirmed.

Approved lists, not general approval

Where a rule asks for an approved ESC, the decision rests with that body's list: EFRA's Approved Blinky ESC list at EFRA events, and the ROAR Approved List at ROAR-sanctioned events, where ROAR rule 8.14.4.1 (as updated in October 2024) makes it the driver's responsibility to know whether the ESC is on the most recent list. A controller on one body's list is not thereby accepted by another. See approved equipment lists.

Speed controllers in recall notices

At least one regulator has recalled ready-to-run vehicles over a speed controller fault. In US CPSC recall 17-139 (25 April 2017) the regulator stated that a 40-amp electronic speed control fitted to some 1/10 remote-controlled vehicles could fail and short-circuit, a fire hazard, and recorded 19 reports of the ESC catching fire. The details, including the firm, are on recalls. A part on fire needs the emergency services; this site gives no firefighting or repair steps.