Of rolling smoke and flaming stacks

There's nothing quite like diesel smoke to grab the attention of romanticists and regulators.

A generation ago, when songwriters discovered that they could make hit records by singing about trucks, they penned lyrics like this excerpt from an old Dave Dudley song:

Well my rig's a little old,
But that don't mean she's slow.
There's a flame from her stack,
And the smoke's rolling black as coal.
My hometown's coming in sight,
If you think I'm happy you're right.
Six days on the road and I'm gonna make it home tonight.

Back in Dave Dudley's day, black smoke was a sign that big rigs were running. If the engine wasn't belching, the truck driver wasn't rolling — and he wouldn't make it home that night.

Today, it's not okay for diesel smoke to roll black as coal. Thanks to tighter emissions regulations — past and future — diesel smoke is becoming as obsolete as the dinosaurs that died and gave us crude oil. Even engines that merely roll smoke as gray as Grandma are no longer acceptable. In a few weeks, when new federal diesel emissions regulations take effect, what comes out of that stack will have a lot more in common with water vapor than it ever had with coal.

But let's take a look at another part of Dave Dudley's engine operation — the flame coming from the stack.

Dave's diesel engine shot flames into the sky, undoubtedly a source of concern for the early opponents of global warming. Next year's exhausts won't look quite like that when they spend six days on the road. Flames won't shoot directly out of the stack, but the 2007-compliant engines will have fire a little further upstream in the exhaust system. Periodic burning will occur inside the diesel particulate filter where the muffler used to be.

But just because we can't see the flames does not mean that the exhaust gases won't be fiery hot. When soot builds up and the filter needs cleaning, diesel fuel will be injected into the trap to incinerate the particulate that has been collected. During this burning process, the temperature of the exhaust will exceed 1000°F, hot enough to ignite (if not melt) a variety of substances that exhaust systems might contact.

Exhaust system temperatures have had truck engineers concerned for some time. It was a major topic of discussion at the 2005 NTEA Truck Product Conference. After learning about the exhaust temperatures, truck body manufacturers and truck equipment distributors immediately began to be concerned about potential lawsuits and disgruntled customers created by the elevated temperatures.

But each time the chassis manufacturers have made presentations to the truck equipment industry — at the 2005 Truck Product Conference, at The Work Truck Show in March, and again at the most recent Truck Product Conference a couple of months ago — they seemed to have a little better handle on how to tackle the heat issues. Truck OEMs are using slightly different methods to keep their exhaust systems from starting fires or causing burns. Our story that begins on Page 30 provides the latest information on how truck manufacturers have modified their exhaust systems to accommodate the new emissions regulations — and what effect these changes will have on the truck equipment industry.

Of course, the effects of the 2007 engines reverberate well beyond these particular concerns of the truck equipment industry. Because the new exhaust systems will be significantly more expensive to buy and are expected to cost more to operate and maintain, customers are buying early. Meanwhile, those who sell trucks are bracing for the pre-buy aftermath.

Remaining to be seen: What effect will this have on trailer demand? With customers cutting their purchases of new trucks in 2007, will truck fleets buy new trailers instead?

Although production of new diesel trucks remains strong, new sales appear to be in the early stages of decline. Pundits are predicting that truck sales will drop 40% next year when trucks equipped with the new exhaust systems will be the only new vehicles on dealer lots. If so, this could be the most severe regulatory-induced downturn for our industry since 1975 when mandated antilock brake systems slashed shipments of truck trailers by two thirds.

The downturn, however, should not last long. After all, we have another round of tighter emissions regulations coming in 2010 — which should trigger another pre-buy as early as the fourth quarter of next year.

While engine manufacturers have not definitively announced what type of technology will be used to meet the 2010 regulations, many expect European technology to be employed. This approach calls for the addition of a separate tank filled with a solution of urea. Injecting the liquid into the exhaust stream has been shown to be effective in cleaning engine exhaust. But we wonder what Dave Dudley would say about driving a rig that sprays urea.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.