thomasmnile wrote:
Shiner: interesting observations. I'm wondering if rolling coal is a fad whose time has come and gone. There is no emissions testing mandated by Florida; there might be local testing in Southeast Fl counties. I haven't even seen a coal roller with the asinine 6 or 8" stack protruding out of the truck bed in I don't when? What happened?
That is because there less of the old (non-common rail) diesels on the road as time goes by. When people hear about a modern diesel being deleted, most ignorantly think of old diesels rolling coal everywhere they go. This is not the case because the DPF, EGR, and SCR were not the only devices added to modern diesels to keep emissions and PM down.
Black smoke is essentially unburnt fuel because you do not have enough air for for the amount of fuel being dumped and/or it is too much at once to completely burn it. The more fuel/power you add, the more it will blow black smoke. This is one of the reasons why old diesels were very low on power because they had to comply with PM standards that took effect back in the early 90's.
Basically, older non-high pressure common rail diesels operated at low psi compared to common rail diesels. The HUEI pump 7.3L maxed out at around 3,000 psi and the HEUI pump 6.0L maxed out at round 3,600 psi. Old Cummins p-pumps maxed out at round 5,000 psi. All of todays common rail diesels max out at over 25,000 psi and some of the latest diesels are over 30k psi. Higher pressures means better atomization of the fuel which means a more complete burn which means less smoke.
Old diesels also had one injection event so it dumped a lot of fuel all at once which coupled with lower pressure (less fuel atomization) means a lower power tolerance for black smoke. They essentially had to keep fuel/power low to keep them from rolling coal and even slight power gains would make them do so. Modern diesels have multi-fire injectors that can fire multiple times for a more complete burn and lower NVH since there are smaller multiple "bang's" during a cycle rather than one big one. There is generally a pilot injection to get the combustion needed and multiple injections as the piston is travelling down. This burns the fuel more completely meaning less black smoke.
You also have turbo technology differences such as faster spooling ball bearing turbos, better blade designs, and variable geometry to get more air in at lower rpms to keep smoke down as well. The quicker you get more air to burn the fuel, the less black.
These are some of the main reasons why even modern deleted diesels will not smoke as bad as older diesels. Fords especially got a bad rap because they did not switch to high pressure common rail until the 2008 with the 6.4L while Cummins did it in 2003 and the Duramax has always been common rail. Of course there is a fuel/power limit to where you will blow black smoke in a modern diesel, but that fuel/power limit is much higher than older diesels.
In most cases, if a modern deleted diesel is blowing a ton of black smoke, then he is either having some sort of engine issues, is on too hot of a tune well past the limits of his turbo, or the purposely tuned it that way(which makes them an a-hole) by removing the multiple injection events. On my 400hp to the wheels tune, there is absolute no smoke even if I go wide open throttle. At around the 450-475 hp to the wheels mark, there might be a slight puff if I go wide open from a dead stop or from a lower rpm with low boost, however, it quickly goes away within seconds once the turbo spools up. At 500+hp to the wheels, it is the same scenario as the previous level, but with a more black smoke initially that starts to clears up once the turbo spools to catch up with the fuel being dumped. It is not a ton of smoke though, and no where near what the old diesels would do when turned up.
Here is a good video showing the differences. Keep in mind that this is with the stock turbo and mine has a lot more airflow than stock.
Anarchy diesel EFI live CSP5 cummins tuning (stock, tow, street, hotstreet, race)
