Today, Davis Technologies is one manufacturer of ETC that is "sensorless" and so small and portable that it's not much bigger than a 9-volt battery. According to Shannon Davis, the unit's designer, "Power is sourced from the original +9-volt battery, and the timing is adjusted through the battery case to the chassis ground." That is, this portable unit detects wheelslip via a close monitoring of an engine rpm (tach) signal, and then retards ignition timing to "soften" the engine power. Damped engine power reduces torque to the driving wheels and therefore assists traction. This unit currently does not have to be permanently hard-wired into the car's harness. Thus, tech inspectors can cut away on ignition controls, claim or swap them out, or apply engine seals to wiring connector junctions till their hearts are content that they're policing ETC. But they will be hard-pressed to detect this portable unit that is separate from the ignition control's internal circuitry and can be temporarily jacked into the car's wiring harness.
Miniaturization = Minimal Detection
A few years ago an ETC unit was typically cobbled up by cannibalizing various MSD Ignition circuit boards out of their factory packaging and retrofitting them into one of the main ignition control spark boxes. This may still be done at the more local levels of racing. For instance, an off-the-shelf timing retard circuit board, or rpm limiter (controlled misfire) circuit board, can be piggy-backed inside the spark box, activated by a push button on the steering wheel, and then the racer could still be the sensor/activator.
ETC packaging evolution over the past few years. The Davis Technologiesred biscuit at righ
A next step in the ETC circuitry evolution was to control the activation/ deactivation of the timing retard circuit, or rpm limiter circuit via a "window switch," which turns the circuit on at one preset RPM and turns it off at another. These circuits were still typically mounted inside the spark box. Sometimes this timing-retard circuitry, or controlled misfire circuitry, would be extracted from the factory packaging and installed elsewhere in the car (say, for example, in the seat), if tech inspectors decided to open up spark boxes and see if they were just a bit too stuffed with electronics.
But within the past few years, there came on the market ETC not integrated in an ignition control. This packaging refinement occurred because the inspection processes became more thorough. Some sanctioning groups have gone to a "claimer rule" where they can randomly take an ignition control, or they issue a racer one from the track, or the ignition control gets inspected with a saw. Racers risk losing a relatively expensive ETC unit if their number is in the claimer pool and they have an integrated ETC/ignition control unit. Consequently, the move to making portable ETC, or designing it so small it can be folded into a wiring harness and look only like a bulge in a loom, or pocketed and removed from the car post-race.