Design Goals:

One of the main ways to improve the efficiency of the engine is to use a lean air-fuel mixture. A lean air-fuel ratio decreases the work output and fuel consumed. In order to obtain the desired lean AFR, an electronic fuel injection (EFI) system will replace the stock carburetor system. EFI systems have been proven to be more efficient than carburetors due to their precision control of fuel. Additionally the EFI is capable of altering the pulse width and ignition timing of the injection. The combination of ignition timing and pulse width ensure that fuel injected is being used with minimal waste. The pulse width is the length of time the injector is open and firing into the combustion chamber and is a part of the AFR control. The ignition timing will ensure the air-fuel mixture will be injected at the right time for the maximum work output.

Design:

 The fuel injection system that will be used is a modified version of the Ecotrons Junior 206 Engine Fuel Injection Kit. The only part in the kit that will need alterations to fit the modified engine is the throttle body adaptor. The throttle body that comes with the kit is 28 mm in diameter, however the intake port on the donor head is smaller than that of the Junior 206 at 20 mm. The modified throttle body adaptor has the same geometric relations, injector mount, throttle body adaptation and nozzle angle, as the stock adaptor. The MAP and O2 sensors working in parallel control the pulsewidth of the injection which ultimately controls the AFR. The ignition timing is controlled by the data obtained with the HALL sensor, which monitors the crankshaft position and speed. The main form of testing being conducted is with a Land & Sea’s DYNOmite Kart Dynamometer. Tests were conducted on the validity of data from the dynamometer at 1 hp and it was found to have negligible impacts on the results, contrary to initial beliefs. To determine the optimal operating conditions during EFI tuning the brake specific fuel consumption will be calculated.