Search Results

This paper describes a detailed study into the use of a pitot probe to measure air flow around an inlet valve under steady state conditions. The study was undertaken to assess the feasibility of the method for locating areas of a port and valve which may be contributing to a poor overall discharge coefficient. This method would provide a simple and cheap experimental tool for use throughout the industry. The method involves mounting a miniature internal chamfer pitot tube on a slider attached to the base of the valve. The probe can traverse the appropriate area by rotating the valve and moving it along the slide. Changing the probe allows measurements in different planes, allowing the whole region around the valve to be surveyed. The cylinder head complete with instrumentation is mounted on a steady flow rig. The paper presents the results obtained at different valve lifts on a production cylinder head.

This paper describes the development of a drive-by-wire throttle system as an automotive research tool. The microprocessor based controller samples engine speed and driver demand (via accelerator pedal position) and utilises look-up-tables to determine the throttle position as a function of both of these input parameters. The inclusion of engine speed as an input to the function facilitates infinite freedom in the design of the ‘demand map’ within the constraints of the engine's performance limits. The system scheme is described, including a novel safety circuit which disables the engine in the event of a system failure. The principle of calibration is described along with a quick technique of validating a new demand map design on a sophisticated DC chassis dynamometer. The importance of the ‘demand map’, especially in relation to driveability, is discussed along with the prospects for exploiting this technology in vehicle development and on production vehicles.

Accurate measurement of a vehicle's resistance to straight line motion on a road (road load), and the separation of this resistive force into its contributory components is of fundamental importance for the calibration of a modern chassis dynamometer and to provide the data required for vehicle performance assessment. The coastdown and steady-state torque tests are the established means of determining the road load on a test track. Differences in vehicle operating conditions and the instrumentation used during the tests lead to variations in the values obtained for the coefficients in the road load equation. This paper describes an investigation into these test methods to determine their relative accuracies, and to compare the results obtained in the different modes. On vehicle anemometry is used to improve the overall accuracy achieved in both types of test.