Rolling coal

Rolling coal is the practice of intentionally disabling the Clean Burn Programming of a computer controlled diesel engine, so that the vehicle can emit an under-aspirated sooty exhaust that visibly pollutes the air. It also may include the intentional removal of the particulate filter. Practitioners often additionally modify their vehicles by installing smoke switches and smoke stacks. Modifications to a vehicle to enable rolling coal may cost from $200 to $5,000.