Abstract: A novel and improved engine data system for collecting, displaying and analyzing engine/vehicle data is provided. The system have advantageously results in a more effective, convenient, portable and low cost method of monitoring and processing vehicle data. The vehicle data system includes a handheld computer containing operating system software adapted to operate the handheld computer in accordance with a data protocol different from a vehicle bus protocol and a handheld microprocessor for executing the operating system software. The system importantly includes an adapter for creating a data pathway between a vehicle bus connector and an external data port provided on the handheld computer which is physically incompatible with the engine bus connector.