The lumpy idle feature lets you create the popular “idle chop” sound by swinging ignition timing rapidly back and forth at idle.
By controlling how quickly timing moves between advanced and retarded angles, the engine produces a sharp, uneven rhythm instead of a smooth idle.
On MaxxECU, the default timing response rate is fixed and relatively slow, which makes the idle oscillate smoothly rather than chop aggressively. Other tricks (fuel cuts, ignition cuts, timers) don’t replicate the sound. Technically, the ECU can already move ~20° per ignition event - enough for the effect. But to achieve the sharp chop users want, it’s recommended to expose faster timing response settings or use RPM FAST instead of the averaged RPM signal for quicker reaction.
Example setup
Use RPM FAST instead of the regular filtered RPM because it reacts instantly to each crank tooth, giving the sharp response needed for quick timing jumps. The normal RPM value is averaged and too slow for creating the chop effect.
