When it comes to engines, the term "deleting" refers to the removal of one or more of the emissions control devices that the engine came with. When an emissions device is "deleted", the device and any other relevant components in question are physically removed and the engine is then re-tuned to run without said device.
"Deleting" is different from "defeating" in the sense that "deleting" refers to physically removing emissions devices, but "defeating" involves disabling emissions devices while leaving all of them in place on the engine. For example, an
EGR (exhaust gas recirculation) cooler can be defeated by
welding it
shut in some spot or blocking it off from one or both ends by inserting a metal plate between the cooler and the exhaust or intake
manifold.
DPF's (
Diesel Particulate Filters) can be defeated by being
drilled out or by installing bypass pipes.
On
Diesel engines, people who do deletes will typically remove
EGR (Exhaust Gas Recirculation) systems and
DPF's (Diesel Particulate Filters), as these two systems are infamous for drastically increasing a Diesel
engine's fuel consumption.
Here in Michigan we no longer have any kind of
emissions testing, which means that today you can find quite a few deleted
Diesel trucks, and even some cars and
SUV's, running around in the state.
