Throttle Deposits in Automotive Gasoline Internal Combustion Engines

The performance of an automotive gasoline internal combustion engine (ICE) with multi-point fuel injection systems can be negatively impacted by the formation of deposits on the throttle system. These deposits can affect not only the ability of the driver to operate the vehicle, but also the general performance of the engine. The source of these deposits and the influence of flow around the throttle valve are not well understood in the state of the art literature. The expense and variation associated with vehicle testing create a need for an accelerated and repeatable laboratory engine test to allow the development and evaluation of design solutions that would eliminate or minimize throttle deposits. This paper describes the background of throttle deposits and how it relates to engine performance, and includes a review of the state of the art literature as it relates to throttle and other deposits within an ICE. This paper will also outline the approach and tasks completed to accomplish the objectives of: understanding the source and mechanism of throttle deposits; understanding the influence of air flow around the valve; understanding the influence of exhaust gas recirculation systems, geographic regions, and ethanol blended fuels on throttle deposits; and developing an accelerated test method using an engine test stand to duplicate throttle deposits to allow future design changes to be evaluated.