Developing the Engine for the Edison2 Very Light Car (VLC) Progressive Automotive X-Prize Winner

Edison2 VLC at X-Prize Finals

Edison2 enlisted RAETECH's support for development of the engine to power their entries in the Progressive Automotive X-Prize Contest. The competition's objective is to create a passenger vehicle that achives 100 MPGe* while meeting performance and emissions requirements. Edison2 entered a total of four vehicles in three categories ultimately winning the Mainstream division.

To achieve the goal of 100 MPGe* Edison2's Very Light Car (VLC) required an engine that is both efficient and light. A gasoline equivalent BSFC of 0.4 or better will be required at an 8HP cruise condition. Acceleration requirements of 0-60mph in less than 15 sec demands a peak power of 40HP.

VLC Engine Specifications:
Engine Type Internal Combustion Spark Ignition
Engine Configuration 4 Valve, Single Cylinder
Engine Fuel E85 Ethanol
Engine Size 250cc
Engine peak power 40hp
Engine peak torque 29ft-lb
Engine compression ratio 15:1
Engine boost system Turbocharger
Transmission type Sequential
Number of gears 6

The engine is a modified Yamaha WR250R 1-cylinder 250cc motorcycle engine with an integrated 6-speed sequential transmission. This is coupled to a transfer case with a reversing mechanism and differential.

Engine load control uses a high EGR content and minimal throttling. EGR and throttle are both electronically controlled. The variable geometry Borg Warner turbocharger is run at low boost levels (~6psi) to provide additional power, while the high 15:1 compression ratio provides cruise efficency.

The induction and exhaust systems along with the camshafts are redesigned to increase fuel efficiency. This engine design utilizes the high detonation resistance and extended dilute firing limit properties of E85.

Optimum Power Engine Simulation Tools

Engine performance simulation tools were used to validate concepts and create the initial design. There was no time in the development schedule for 'trail and error' experimentation. The design had to be right the first time.

Optimum Power Technology's Virtual Engine 1d engine simulation tools performed intake and exhaust manifold optimization and camshaft geometry tuning for the intended operating range. Thousands of iterations of intake and exhaust runner geometries could be evaluated using simulation before cutting metal. Inlet and exhaust runner diameters and lengths were defined as variables which were tuned and optimized during the simulation process.

Edison2 VLC Engine CAD Model

Both overall package design and detailed component design were performed using Solidworks 3D modeling tools. Body and chassis fabrication occurred simultaneously hundreds of miles away, sharing cad models insured everything fit correctly when the engines were installed.

The RAETECH VLC engine uses a 32mm Bosch DV-E5 electronic throttle body, computer controlled EGR Valve, custom designed EGR Cooler, camshafts from Comp Cams, Peterson Valve Springs.

The engine controller is a Motec M880 ECU. Fuel control is based on throttle position, manifold pressure and temperature. EGR flow is measured using an orifice flowmeter to provide mixture compensation and ignition timing adjustment. A three-way catalyst is used for exhaust after treatment and a wideband Bosch O2 sensor provides closed loop mixture trim. The high flow EGR system utilizes a tube in shell cooler and a stepper motor controlled EGR valve.

Edison2 VLC Engine Installation

The Edison2 VLC performed successfully at the Progressive X-Prize Finals meeting all the goals, winning the Mainstream Category.

  • 0-60 in 14.2 seconds
  • Highway Fuel Economy 129 MPGe*
  • Combined Fuel Economy of 102.5 MPGe*

* MPGe is calculated based on the energy consumed equivalent to 1 gal of gasoline.