DIESEL EMISSIONS


air from the charge air cooler is mixed with recirculated exhaust gas which has been cooled in the EGR cooler. The fresh air and recirculated exhaust gas are blended by an EGR Valve. Looking at the drawing below, you can see how the air and exhaust are routed in a diesel engine.


There are certain parts which can malfunction and affect the diesel particulate filter. If fuel injector timing is not correct, if the injector malfunctions and does not atomize the fuel or leaks into the combustion chamber too early or too late it can cause incomplete combustion that results in white or black smoke. A leaking intake or exhaust valve will also cause a fuel rich burn sending unburnt fuel into the exhaust system, making the exhaust almost moist. This causes a problem with the diesel particulate filter because it is not designed to catch this type of mixture in the exhaust. Remember the DPF was designed to catch soot and particles produced in a properly operating combustion chamber of the engine. Along with the soot produced by the fuel, there is a certain amount of ash that is produced from the oil that lubricates the engine parts. In the last issue of this magazine, we talked about the importance of using the newest oils that were designed for reducing ash in the exhaust stream.


If an EGR Cooler develops a leak, the coolant enters the engine exhaust through the EGR valve and is exhausted from the engine into the exhaust stream thus producing a different type of ash which will prematurely clog the diesel particulate filter.


If a charge air cooler leaks beyond the manufacturer’s specifications it can cause the following issues:


• Increased fuel consumption • Low engine power • Excessive soot in the oil • An increase in DPF regenerations • Premature piston, ring and valve failure • Elevated coolant temperature


• Frequent costly repairs of components like turbo and exhaust manifolds


There are a couple of interesting side effects caused by a leaking charge air cooler. If you look at the list you will see excessive soot in the oil and increased DPF regenerations, which means the DPF is getting plugged and premature wear of the turbo.


Lastly, any of these components can cause excessive strain on the turbocharger of a diesel engine. The turbocharger is receiving the exhaust heat in order to turn the turbine that produces the boost of the fresh air that is being circulated through the charge air cooler and finally into the engine. If any of the previous malfunctions occur which include fuel injectors, EGR coolers and charge air coolers, the diesel particulate filter can prematurely plug leading to excessive back pressure on the turbo. If the exhaust gas cannot flow freely through the turbo and out the exhaust system, the turbocharger operates at temperatures higher than what it was designed for, which can lead to premature failure.


Can a diesel particulate filter cause a turbo charger failure?


If the diesel particulate filter is blocked and passive regeneration does not clean the filter or frequent regeneration starts to


occur this is an indication the turbocharger is having a greater amount of heat and back pressure placed on it. The free flow of exhaust needs to happen to prevent the heat build up which can cause the lubricating oil in the turbo to carbonize and clog the oiling system. If the oil carbonizes and blocks the lubrication then this is the beginning of the end for the turbo charger as the bearings will start to suffer.


As a diesel particulate filter service business, you must educate your customers and express the importance of having a preventive maintenance program that establishes regular cleaning cycles based on miles driven or time operated. This type of maintenance can be saving your customer’s turbo chargers and charge air cooler cleanings. When turbochargers fail they may spew oil into the charge air cooler thus requiring additional service for the charge air cooler. Regular pressure tests of charge air coolers is also advisable as leaking charge airs can also have an effect on all of the related components.


Hopefully your technicians can achieve a basic level of diesel engine emissions knowledge, so they can better understand the importance of clean filters and better communication with the customer.


November/December 2021 | THE COOLING JOURNAL | 15


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