Over the last five years, almost every major manufacturer has released new excavators and wheel loaders boasting the same horsepower but with significantly lower maximum RPMs. An engine that used to redline at 2,200 RPM might now be electronically capped at 1,800 RPM. This is called engine downspeeding, and while it's a brilliant engineering feat for fuel efficiency, it is causing massive confusion-and engine damage-in the field.
To get the same power out of an engine turning fewer revolutions, engineers had to increase the torque output by using higher-pressure common-rail fuel systems and different turbocharging setups. The engine makes its massive power down low in the RPM range, allowing the machine to use less fuel during standard digging cycles.
The problem is that operators are not sensors; they are used to feeling the engine "rev up" to know the machine is working hard. Because the new engines are capped at a lower RPM, operators are intentionally lugging the machine-pushing the joysticks into heavy dirt while the engine is only turning 1,200 RPM. In a mechanical engine, lugging just blew black smoke. In a modern high-pressure electronic engine, lugging creates extreme cylinder pressure and exhaust gas temperatures. Because the engine isn't spinning fast enough to flow air through the aftertreatment system, the Diesel Particulate Filter (DPF) plugs up rapidly, and the high exhaust heat can melt the turbocharger turbine blades. Fleet managers are having to completely retrain operators to stop treating the throttle like an on/off switch and actually let the engine RPMs climb into the newly designated "work band" before putting the hydraulics under load. You cannot drive a downspeeded engine like a 1990s mechanical tractor.
