Rolling coal is the practice of modifying a diesel engine to increase the amount of fuel entering the engine in order to emit an under-aspirated sooty exhaust that visibly pollutes the air. It can also 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 cost from $200 to $5,000. -- Wikipedia

By:Jake Lingeman - Jake Lingeman is Road Test Editor at Autoweek, reviewing cars, reporting on car news, car tech and the world at large.

http://autoweek.com Posted JANUARY 27, 2017

HB11 looks to pull the plug on souped-up diesels

“Rolling coal” could become illegal in Maryland as a bill makes its way through the state House of Representatives on Thursday. “Rolling coal” is a slang term for when diesel drivers tune their pickup trucks to spew black smoke from the tailpipe on acceleration. It sometimes entails increasing the power output of an engine, and it usually necessitates the removal of some emissions parts. We’ve seen videos of these guys (it’s always guys) doing this while they pass other drivers, runners or bicyclists on the road.

The bill states that it’s illegal for a driver to cause “a diesel–powered motor vehicle to emit certain clearly visible emissions onto another person or motor vehicle; providing for the application of this Act; and generally relating to a prohibition on the discharge of excess diesel–powered motor vehicle emissions.”

Ezra Finkin, director of policy of the Diesel Technology Forum, testified before the Maryland General Assembly House Environment and Transportation Committee in support of House Bill 11:

“Diesel engines have long been a popular option in heavy-duty pickup trucks because of their superior fuel efficiency and towing performance. While we recognize diesel enthusiasts' love for diesel engines and the performance of their vehicles, the practice of tampering with engines and emissions controls for the purpose of generating excess emissions on demand -- ‘known as rolling coal’ -- is offensive, unsafe and harmful to the environment. Most of all, it is not representative of the manner in which diesel engines were designed to operate.”

The bill exempts drivers of commercial vehicles with a gross weight of 10,000 pounds or more and construction vehicles. It also exempts drivers of standard diesel-powered cars that discharge visible exhaust during normal acceleration.

The bill falls under Maryland’s Section 203(a)(3)(A) of the Clean Air Act that explicitly forbids the practice of tampering with a vehicle’s emission controls and allows states to prohibit the practice.

On a personal note, we think the practice is dumb and the drivers who do it are dumber. We love tuning cars, adding parts and taking them away. But it’s always in pursuit of something nobler: speed, handling, comfort, or even efficiency. It’s never to pollute needlessly and never to anger other people on the road purposely.

To what end, we ask you coal rollers, to what end?