SPC5-L9177A-K02 Small Engine EFI (Electronic Fuel Injection) Reference Design for SPC572L MCU and L9177A Driver (Image courtesy of ST Microelectronics)
Small engines, in this case, are single- and twin-cylinder gas engines such as motorcycles, three-wheelers, scooters especially in China, Europe, and India which are the top three largest users in the world. These countries also demand by law that these vehicles must satisfy upcoming Euro 5, Bharat Stage VI (BSVI), and China IV.
What is the advantage1 of Electronic Fuel Injection (EFI) for these small engines?
Instead of using a legacy carburetor, many manufacturers are moving towards EFI designs that inject fuel directly into either the engine manifold or the cylinder. EFI has been an industry standard for the last 30 years and now lawn mowers and turf machines are gravitating towards this design.
The obvious reason to make the move to EFI is better fuel economy. Landscapers and even homeowners know how expensive gas is and the price is not going down much. Other advantages of EFI are faster starting, especially in hot and cold restarts. Landscapers value their time and want to get on to the next job. Homeowners also want to get back to that baseball game on TV too.
One little known advantage of EFI is that in places like Denver, the process of mixing the fuel with oxygen (Thinner air at mile high Denver and other places) makes a carburetor struggle. EFI designs compensate for this.
Carburetors also have difficulty supplying a constant power drive to the wheels, but EFI systems employ an Engine Control Unit (ECU) that looks at the speed and load conditions and adjusts the fuel flow to rectify this.
Lawn mowers and even small motor bikes, if sitting around for a long while, can get the fuel ‘gumming up’ a carburetor and making starting a difficult task. EFI systems atomize gasoline into a fine, efficient mist which leaves less fuel behind and helps prevent rebuilding and cleaning those carburetors.
Finally, we all want more horsepower in our vehicles. EFI delivers more horsepower that carburetors.
The ST Micro reference design has ready-to-run reference design examples in ST’s SPC5Studio.
The ST reference design uses a L9177A automotive peripheral on chip for low end engine control in a TQFP package.
1 The advantages of EFI for small engines, Chris Boll, OPEREVIEWS.com, July 12, 2018