MARKHAM, Ont. –A leaking exhaust system may not be best practice, but for the longest time it has been part of the reality for many trucks on our roads. That reality is going to have to change, however, under the new engine emissions standards or it could prove a costly oversight.

“The days where you could run a unit with an exhaust leak are gone. They need to be fixed immediately or you will ruin the DPF (diesel particulate filter),” warned Dan Hrodzicky of Texis Truck Exhaust during a panel session on the 2010 engines at this year’s Canadian Fleet Maintenance Seminars. The 2010 emissions standards demand significantly reduced levels of nitrogen oxides (NOx) and particulate matter (PM). Engine manufacturers are able to employ higher exhaust gas recirculation to reduce the NOx but must use regeneration to deal with the required cuts to PM. The need to use an aftertreatment device to replace the muffler, however, has also reduced the level of exhaust modification flexibility enjoyed in the past, Hrodzicky pointed out.

During passive regeneration, exhaust temperatures are hot enough to burn soot and turn it into carbon dioxide and water, greatly reducing filter backpressure. The distance from the turbo to the aftertreatment device must be controlled within prescribed limits.

During active regeneration the temperatures of the exhaust gas in the aftertreatment device and the tailpipe will also be high. Regeneration can last from 10 to 40 minutes, Hrodzicky explained, with the temperature on the skin, body and V-bands of the aftertreatment device ranging between 250 and 300 degrees Celsius.

“The aftertreatment device and tailpipe will need to be stainless steel and have a double wall and/or insulation to maintain acceptable surface temperatures of approximately 250 C,” Hrodzicky said, adding that tailpipe gas discharge temperatures may need to be controlled using diffusers.

The piping material used in the exhaust system will primarily be 409 stainless steel. Aluminized mild steel can’t be used for the main pipes because it can’t meet the requirement for a 435,000-mile useful life or the higher temperatures. The pipe from the turbo to the aftertreatment device should also be double-walled to optimize heat transfer.

Abnormally frequent regeneration and/or loss of power are signs that engine maintenance is required, Hrodzicky said. Most engine manufacturers recommend maintenance and cleaning of diesel particulate filters between approximately 190,000 and 320,000 kilometres (less for severe-service applications).

“A new diesel particulate filter costs between $3,000 and $8,000. Regular cleaning helps extend the life of your filter,” Hrodzicky said.