Implementing Variable Valve Timing on a Research Engine: Development and Implementation of a Turnkey Variable Valve Timing Solution for a Research Spark-ignited Engine

Abstract

Four-stroke combustion engines operate at a variety of speeds, typically between 1000 rpm and 7000 rpm, affecting the flow of gases in and out of the combustion chamber. Flow of gases is controlled by opening and closing of poppet valves. This opening and closing is typically done by a camshaft driven by and running syn chronously to the crankshaft. Variable valve timing (VVT) allows for a dynamic (while operating the engine) phase between camshaft and crankshaft, allowing dy namic changes in gas exchange and engine characteristics as different valve timing is preferred at different engine speeds and loads.

This thesis covers the development of a VVT control system for an AVL one-cylinder four-stroke engine located in test cell C at The Division of Energy Conversion and Propulsion Systems (ECaPS) at The Department of Mechanical Engineering (ME) at Chalmers University of Technology. The development is based on the engine’s existing hardware, such as crankshaft and camshaft sensors, hydraulic channels and VVT solenoids controlling oil flow; therefore, this project has covered the develop ment, manufacturing and installation of a control system and complete electrical installation.

The control system was developed iteratively with five rounds of prototyping and testing, aiming to produce a working product fulfilling user requirements of being stand-alone, simple, robust, and based on standard components.

The final product is the control system, based on a Teensy 4.1 microcontroller, which allows the user to perform independent on-the-fly cam phasing. Although it was not possible to procure the necessary cam gears to implement the hardware side of the solution, the system has proven itself during real operating conditions, connected to the engine test rig.