What factors contribute to carbon formation on inlet and exhaust valves of a diesel engine?
Most contributing factors of carbon formation in the combustion chamber and valves are poor combustion caused by poor injection and/or lack of scavenging air supplied. Such conditions caused by:
1. Prolonged operation at low load and low temperature
At low load and low temperature, the turbocharger efficiency drops and the quantity of air supplied to the engine reduces. This results in improper combustion and hence large amount of carbon formation takes place in the combustion chamber. When running at low load, the exhaust gas pressure and exhaust gas energy are not sufficient. Hence there will be backpressure exerted on the exhaust. If the same overlap is maintained between exhaust and inlet valve is maintained during that time, then when the inlet valve opens the exhaust pressure is not sufficiently dropped. Under such circumstances, there will be back-flow of exhaust gas from the cylinder into the air inlet valve before the actual flow of the inlet air to the unit starts. During this time, the formation of carbon takes place in the air inlet valve.
Operation at low loads and temperatures should be avoided as much as possible.
2. Faulty fuel injectors, fuel pumps, Turbocharger
All engine components must be inspected and maintained timely in accordance with maker's recommendation and best practices to avoid deviation of an operational parameter from design.
