4-Stroke EFI Basics for Snowmobiles: Part 2

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EFI Thinks for Itself

By: Kent Lester

By introducing electronics and computer controls, automotive engineers have been able to eliminate the problems carburetors have been wrestling with for years.

For instance, with EFI, no choke system is necessary and the fuel and air flow balance is always consistent despite weather conditions or the temperature of the engine. Fuel flow is near perfect on every stroke of the engine and fuel is not wasted as it “puddles” in a manifold waiting for a valve to open so it can enter a combustion chamber.

The result is an engine that starts easier, idles with precision and accelerates at any RPM level without hesitation. Is the exhaust cleaner? In most cases it is.

How does it work? Back to the aerosol sprayer mentioned in Part 1. If your finger could press and release the nozzle hundreds of times per second and time the pulses so they fall exactly at a pre-determined point, you’d be doing what EFI does.

In order for this precision pulsing to take place, an EFI system has to be able to “read” several conditions. This is accomplished by using a team of electronic sensors located on or within the engine and exhaust system.

The data accumulated from these sensors is channeled to a “brain” or Engine Control Unit (ECU) where the information is processed and the decision as to how long the injector should stay open is made and how much fuel should be squirted in relation to the air flow available.

The ECU also controls engine timing so the injectors are squirting at the engine’s optimum time window to maximize fuel efficiency and power depending on its load.

The Engine Control Unit (ECU) controlling a snowmobile’s EFI system is really a computer that processes the feedback it receives from a fleet of electronic sensors and then chooses the duration and frequency of the pulses the fuel injectors should be spraying gas.

This tiny “black box” is well hidden within the snowmobile’s wiring network and protected from the elements.

Like any computer it contains programs or “maps” that process data and apply it as required. These data maps are created by the manufacturer and are programmed into its complex database.

They detail every possible scenario of outdoor and internal engine temperature, fuel flow, air flow, existing power, load demand and every other conceivable possibility at every RPM. These calculations and adjustments are processed thousands of times per second.

Keep checking back for more on this 4-part series about the basics if Snowmobile EFI technology.

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