Trends in tribological materials and engine technology

Wear mechanism study of exhaust valve system in modern heavy duty combustion engines

“…The removal resulted in heavy wear, especially on the exhaust side. Research proved that the lead reacted and formed complex lead oxides on the valve and seat surfaces, these had beneficial friction properties and protected the surfaces [3,4]. In absence of the lead, a brittle iron oxide formed.…”

Determination of wear in internal combustion engine valves using the finite element method and experimental tests

“…Furthermore, the lead deposits formed between the contact areas of the valve and the VSI lubricated and cleaned these surfaces which helped to reduce the wear between the parts [2,3]. However, current environmental laws impose severe restrictions on the emission of NO x , and the use of lead in gasoline for cars and trucks engines has been eliminated since 1993.…”

Possibilities for reducing tractor engine friction losses at cold start using an ultrasonic irradiation technique

“…Although cold start lubricating conditions are not critical for the crankshaft bearings, other engine components such as the camshaft, lifters, connecting rod bearing, piston pin, piston, piston rings, and cylinder walls are not fully lubricated in the time it takes for the oil pump to pressurize the lubrication system and supply the necessary oil to the engine (Livanos and Kyrtatos 2006). The common solution for this problem is the use of engine lubricants with additive technology (in combination with higher quality base stocks) that assure the necessary oil viscosity for all temperature start conditions (Becker 2004;Fox 2005;Leong et al 2007). This can help to maintain adequate engine wear protection during extended operation and under the more severe conditions of an engine cold startup process, as Plomer and Benda (2000) and Katafuchi and Masai (2009) have shown.…”