EXHAUST SYSTEMS
Big Cat Mufflers Need Special 'Packaging'
Tom Berg
Equipment Editor
'Packaging" of bulky components on sometimes-crowded truck frames is becoming more an issue as new Caterpillar diesels appear. Clean Power engines built since October 2002, as well as most ACERT diesels due out this year, require large catalytic converters to strip exhaust of minute pollutants left over from combustion.
The converters are combined with mufflers to save some space. But to get enough catalyst volume, the converter/muffler combo is bigger than a muffler alone.
The easiest way is to hang a single converter/muffler on the frame, with a short tail pipe exiting right there. This is not always possible, especially on short-wheelbase tractors or trucks with pusher-type lift axles.
Also, road salt and grime beat on the appliance and hasten the day when it must be replaced. This is not a big deal with a $100 or $200 muffler, but is a real issue now, because a converter/muffler costs about $1,000.
Dual exhaust stacks are the next easiest way. Builders are reportedly choosing that route for big-bore (10 liters and up) Cat engines. Converter/mufflers are 10 inches in diameter, as before, and fit OK at the cab corners.
Customers who want to stay with one exhaust stack are faced with a single appliance that's 14 inches in diameter - too big to fit at a cab corner without extending beyond the body's width. It can go behind the cab, and that works for tractors and trucks whose bodies are not closely mounted to the cab. If the body snugs up to the cab, as with most dump trucks, space has to be made for the exhaust. One solution we just saw at a recent International Truck event is a notched-out body corner. This "cut out" on a J&J aluminum body sat on an International 7600 chassis with a Cat C-12. J&J says the cut-out body and cab shield costs about $500.
We'll see more of these solutions because Cat's C-12 and C-15 are popular among dump truckers. And the upcoming ACERT C11, C13 and C15 will likely also be popular.
A still-unresolved question is how to get exhaust gas to the floor of heated dump bodies. The exhaust cutout used up to now was upstream of the muffler, which was fine because the floor chamber acted as a muffler.
But now the cleansed gas must be taken downstream of the converter/muffler. A frame-mount muffler can be plumbed into the body's floor, but a vertical stack is way out of reach. Body and chassis people are still pondering this.
