With today’s electronic monitoring gauges, the science is a lot more precise. We can now observe the temperature of each cylinder and make sure it stays within the recommended guidelines. But with preignition, monitoring the gauges is likely insufficient, since the damage can be done so quickly. Fortunately, many supplemental systems include alerts, which the user can program for a set temperature, generally somewhere below 400 degrees. However, for systems that replace primary engine instruments, Busch says the FAA has been requiring the manufacturer to hard-wire the alert to the CHT redline, at which point the damage is likely already done. Some manufacturers are working with the FAA to allow a yellow alert for primary systems at a user-selected temperature.