Mechanism of the Deposit Formation at Inlet Valves

The deposits on intake valve tulips of spark ignition and diesel engines can produce an increase in fuel consumption and exhaust gas emission, a deterioration of the driving behavior as well as mechanical defects.

The formation of these deposits is investigated with respect to different engine parameters and by using a commercially available leaded fuel without additives.

The valve deposits are formed by composing and decomposing phenomena which occur in parallel. The composing elements are oil, particles coming from the combustion chamber via the internal exhaust gas recirculation and, partially, fuel components. The deposits are reduced by the liquid fuel coming in contact with the valve tulips and by a high rate of oil flow.

To the end of a shorter test duration and less test efforts a short-time simulation to investigate the deposit formation on inlet valves will be described.