WR450F Engine Syncronization and Ignition System
The ignition system of an engine is designed to ignite the air fuel mixture with a powerful spark. Selection of an appropriate coilpack was critical for performance and reliability of the Formula SAE Vehicle. I chose the General Motor's LS2 Coils because of their simplicity. The GM coils are complete single-cylinder ignition systems and contain the electronics for dwell limiting and current limiting. When using these coils, no ignition module is required as the igniter is built into the coil in a compact package. Because the RPM’s the Yamaha WR450F can reach are much higher than the original LS engine the coils were designed for, a dwell calculator was developed to ensure we would not exceed the maximum rpm of the coil pack. The calculations done to determine the operating condition of the coilpack were done usint equations from Dtec Devices, and ignition data from Megasquirt. The LS2 coils should be able to keep up, even when running in a wasted spark configuration.
​
The Powertrain Team Lead and I decided we wanted to run the engine in a conventional spark setup. This reduced chances of blowing up our 3D printed intake when tuning the engine. Also, because the single cylinder was so electrically power limited, conventional spark configuration would save electrical power as well.
I considered several methods to get full engine syncronization. Reading the cam lobe directly, reading pressure in the intake manifold, and adding a trigger wheel. We found the rising / falling edge reading the cam lobe was not as strong as we desired. We also worried that drop in intake pressure wouldn't be strong enough to get reliable syncronization. A trigger wheel system was developed! The picture's above show the trigger wheel system that was developed for the 2019 WR450F engine. A strong engine syncronization signal is shown on the MoTeC Capture Input's page. We were able to get full syncronization reliably in 1-2 engine rotations.
Nothing ever can go perfectly though! Yamaha sent us a 2021 longblock and the valve cover was completely different. I designed a new trigger wheel system. This one keyed into the cam get similar to the old version, but the trigger wheel was on the opposite side of the camshaft! We passed the rotation through the hollow cam shaft with a hex shaft. A wavespring was used to ensure CTE growth would not stress either component (trigger shaft or camshaft).
We never had problems with engine sync for the entire season, 600+ miles of driving in various midwest temperatures.