grover said:
Can we talk about what defines "coal rolling?"
I ask because I have a 97 F-250 7.3. It is factory stock except for a 5 position switch that I use during towing. When I say factory I mean, OEM size tires, no lift, and factory intake and down pipe. It had 112,000 miles 2 years ago when I bought it and I'm up 176,000 now (I'm a roofing sales manager in north Atlanta that covers Chattanooga TN). Even in the stock position, if I'm towing or getting hard on the go pedal (which I don't do often) I see some smoke out of the tailpipe. It's been like this since before the chip. I have no blow by- etc, I think that's just factory.
my point is that if you drive a diesel, and are towing fairly heavy you are likely to have more visible exhaust at times than a comparable gas vehicle- so is that considered coal rolling?
Coal rolling in general is just overfueling. A stock tune on a diesel like yours that's old enough to predate emissions regulations isn't rolling coal. Some soot under load is normal for those vehicles. When you start changing fueling or timing with your chip, then you do get into illegal emissions modifications though.
There was a similar question in an older discussion that Keith already linked, so I'll just copy my reply from that post to save time:
"People seem to be focusing on coal rolling, but there are tons of people with deleted diesel trucks or tuned gas vehicles that aren't obviously rolling coal, and they're arguably doing more harm to people and the environment. Not all tailpipe emissions are equal in their visibility, their impact on people, or their impact on the environment.
Tailpipe emissions are the result of decisions/compromises in the combustion process. And reducing one bad chemical compound often results in increasing another. Direct injection makes this easier to get right, and also easier to screw up as you can inject fuel multiple times in each stroke, and the timing/amount of these fuel injections controls what you get out of the combustion process. If you want to prioritize fuel efficiency, and run lean, you get high temps and lots of invisible NOx. If you want to prioritize making more HP, or rolling coal, you add more fuel which reduces combustion temps and NOx, but increases hydrocarbon and particulate production.
Each of those compounds does different things once it's out in the world. NOx and particulates are both pretty harmful for humans, so the regulators have chosen to reduce those things first with the trade off being that they increased some less harmful emissions like HC and CO2. Essentially they prioritized human health over the environment in the beginning. Now that the stuff that harms people is mostly controlled, those environmentally harmful compounds are also being targeted for reduction.
Modern diesels have gotten so good at cleaning up the stuff after combustion, that they actually run dirtier combustion than older diesels like your Powerstroke. If you measure immediately after the turbo, they make far more NOx than a pre-emissions diesel and then they rely on emissions hardware to clean it up. That's how you get 1000ft-lbs with a warranty and cleaner tailpipe emissions and basically the same fuel economy as 20 years ago. But, if you delete that emissions hardware that's doing all of that cleanup, you've just got that dirtier combustion process creating more tailpipe emissions. And that's before you start trying to make more power, or roll coal, or increase fuel economy. And as Kieth has said, it could mean increasing emissions several orders of magnitude higher than allowed by law.
So the point is that coal rollers are highly visible for enthusiasts and non enthusiasts alike. But for every brodozer rolling coal and making it obvious that they're breaking the law, you've got several others creating just as much harm without making it obvious. Thats why regulators are going after those who enable and profit from emissions modification. It eliminates all of the offenders at the source."
