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Latest Electronic Fuel-Injection (EFI) Reference Design compliant with new regulations for Small Engines

ST Microelectronics developed a Small Engine EFI reference design and is teamed up with Arrow Electronics to supply these boards quickly to customers. See Figure 1.

Figure 1

SPC5-L9177A-K02 Small Engine EFI (Electronic Fuel Injection) Reference Design for SPC572L MCU and L9177A Driver (Image courtesy of ST Microelectronics)

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.

References

1 The advantages of EFI for small engines, Chris Boll, OPEREVIEWS.com, July 12, 2018

6 comments on “Latest Electronic Fuel-Injection (EFI) Reference Design compliant with new regulations for Small Engines

  1. dick_freebird
    July 24, 2019

    Advantages there may be, but simplicity is not one. That little 1″-on-a-side lawnmower carb becomes a collection of sensors and actuators and of course the “brain”, which freaks out when any of the assembly goes bad. Probably go from magneto to electronic ignition meanwhile, so there's another set of baggage. Your push mower now gets saddled with an alternator and battery to run all that mess, and pushing it all is on you. BOM cost, that's a huge LOSE. BOM weight, I'm sure will far exceed the fractional pound involved in a pot-metal carb and a two-horned magneto.

     

    But it's not about what's good, reliable or maintainable for the consumer. It's about “compliance” and it's between the manufacturer and the feds who have them by the naughty bits, machete in hand. Consumers just get to svck it.

     

    Throwing all this technology at tools that get used for a couple of hours a week is just bureaucratic abuse of the citizenry for negligible benefit to anyone or the environment. Check the energy and materials input to all of that gizmosity (yeah, yeah, fuel economy bleating when the thing burns maybe 100 gallons over its service life, and you're going to improve economy 20%) and tell me that anybody (or their life-cycle-cost-of-ownership) was or will be saved.

  2. Steve Taranovich
    July 25, 2019

    @dick-freebird: I hear you. I understand some of the additional things that this system adds to a lawn mower that might not be earth-shaking and would be more complicated.

    On the other hand, people don't have to buy a lawn mower with this technology if they feel the same way as you do. However, imagine how many lawn mowers there are in the world—one or two or 1,000 may not matter, but add them all up……..maybe it makes a difference in the environment.

    This product makes the biggest difference in products like motor scooters—-I have been in India and Shanghai and if just half of those scooters had this product—how much difference might that make?

     

  3. dick_freebird
    July 26, 2019

    >On the other hand, people don't have to buy a lawn mower with this technology if they feel the same way as you do

     

    When the governments say what can and can't be on the market, this becomes fanciful at best. That's the fun bit about “compliance”.  When's the last time you were offered a carburated powertrain option on a passenger car? Right. Between EPA and CAFE standards-creep the manufacturers are simply forced into complex solutions and the consumer pays the tab or goes without. Yeah, you could buy used, until that pool is depleted.

     

    Now there's other fun such as how these ECUs behave once sensors go bad. Like a fouled HO2S telling the ECM it's dead lean, like they all do someday. Your poor folks who drive those scooters into the ground and throw them on the piles that line the streets of Taipei – going to shell out $100 for a new sensor when the thing starts to throw black smoke and guzzle fuel, if it's still getting them down the road? Nope. More like they'll keep riding and put out worse emissions than a carb motor ever would.

     

    But we are all just pawns and logic does not apply (it's just an applied coating on a deal made by, between our betters).

     

  4. Steve Taranovich
    July 26, 2019

    @dick_freebird: I still like technology that improves a product. But—I do not like everything the government tells us we have to do—-that's why we vote. Our government system is far from perfect in America, but it is still the best in the world.

  5. SPI0
    July 31, 2019

    NOTHING COMES AS A FREE LUNCH, CAN THIS DISCUSSION INCLUDE Ethanol ? Everything seemed to work until Ethanol for small engines, but other engines as well. Phase seperation in gasoline is the root of carbuerator gumming, but will also cause problems in EFI designs.

  6. Steve Taranovich
    July 31, 2019

    @SPI0—There are some problems as you suggest, but take a look at the following:

     

    https://blog.amsoil.com/how-to-fight-ethanol-problems-in-small-engines/

    and

    https://www.ellsworthamerican.com/featured/ethanol-blends-cause-tremendous-damage-to-small-engines/

    It's a debate that's been going on for a while

     

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