48-52,77 6.7L Cummins 9/16/13 4:04 PM Page 52
Feature gas in and hope for the best. On top of the exhaust manifold is mounted an EGR cooler. In order for the exhaust gas to be introduced into the engine, it must be cooled. Exhaust temperature in a diesel engine while towing can become pretty intense. Temperatures in the range of 1,000°F are not uncommon. The cooler is very similar to the function of an engines radiator. Coolant from the engine circulates through the cooler, which has flues for the coolant to pass in order to cool incoming exhaust gas. Exhaust Oxygen sensors are placed in the exhaust system for fuel gas is only introduced into the engine at ceroptimization by the engine tain times when a certain criteria has been management system. meet such as engine speed, mph, coolant temperature, etc. So, the engine is not going to be opening the EGR valve all the time, just when it is needed. ilar, but has changed quite a bit due to the fact of the EGR There is a time where the EGR is going to be needed and system. (I addressed the addition of EGR for the 6.7L earlier that is when the DPF is going to regenerate itself. Rememin this article.) Now let’s focus on the components that are in place for the EGR to function properly. The EGR system is ber as mentioned before, when the DPF regenerates, the EGR is opened to increase exhaust gas temperature. When what introduces exhaust gas back into the intake manifold this process takes place, we really don’t want to cool the exto enter the combustion chamber to be burned again. By inhaust gas with the EGR cooler. So, Cummins came up with troducing exhaust gas back into the intake manifold, NOx the EGR cooler bypass valve. The cooler bypass valve is loemissions are reduced. cated in front of the EGR cooler. The valve is cable actuated At the mouth of the intake you will find several compoby a servo motor that will move the cables which will open nents that need to be explained so you will understand their and close the valve. During the regeneration process, the function for the EGR system. cooler is bypassed so hot exhaust gas can be introduced into The EGR system in a diesel can be quite complex. It’s the combustion chamber to heat the exhaust system to aid not just a matter of opening a valve and letting the exhaust in regeneration. continued on page 77
52 September 2013 | EngineBuilder
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