Gasoline injection could also be virtually common within the automotive world immediately, however small engines are one other story. Although carburetors could also be temperamental and extra obscure, they’re easy mechanical gadgets that value little or no to fabricate and that don’t require computer systems — excellent for lawnmowers, turbines, and different functions the place effectivity and energy output are low priorities. However Carlos Takeshita, a mechanical engineering scholar at UC San Diego, needed his 212cc Predator engine to have gas injection, so he constructed this DIY ECU to regulate the conversion.
That is a cheap 6.5HP engine from Harbor Freight initially used for a mini bike challenge. You may purchase this engine model new immediately for simply $119.99 and it might, in fact, be carbureted. It’s meant for lawnmowers and different easy machines, so low value was possible the highest design purpose.
However Takeshita needed a option to experiment with electronics and firmware, and this engine was the proper platform for that. It additionally gave him the chance to apply a number of the mechanical engineering he was studying at school.
The elements required for the conversion consisted of a gas cell, a gas pump, an consumption manifold, the injector itself, a battery, a customized crankshaft place sensor system, and the DIY ECU. That final half was made utilizing a Teensy 4.0 microcontroller improvement board.
Timing is essential, so the crankshaft place sensor was essential. It’s a missing-tooth wheel made from ferrous metal and the Teensy can monitor its rotation by means of a Corridor impact sensor. The lacking tooth helps the Teensy confirm TDC (High Lifeless Heart) with every rotation. This lets the Teensy management injector timing and will additionally give it the flexibility to regulate spark timing sooner or later, if Takeshita decides so as to add that.
The Teensy is aware of the crankshaft’s place and velocity, and in addition screens a MAP (Manifold Air Stress) sensor mounted on the customized consumption manifold. That knowledge is all it wants and the customized firmware is accountable for controlling the injector by means of a TI LM1949.
However tuning is difficult — particularly with out a option to reliably measure energy output — and Takeshita hasn’t perfected that but. All it takes is tweaking the variables in firmware, so he can experiment as a lot as he likes. Nonetheless, engine tuning is nearly an artform of its personal. Regardless, the engineering was successful and Takeshita achieved his purpose of giving this small engine gas injection.