METRO PLUS

Injecting power





A closer look at the technology that promises to make bikes cleaner and more powerful

History they say repeats itself. In the late 1990's India's tightening emission norms ensured that bike-makers stopped two-stroke production and switched to four-stroke having catalytic converters to help stay on the greener side of the line. Now again it seems the winds of change are blowing across the bike segment, the carburettor's innings are coming to an end and the electronic fuel-injection (EFI) bikes are ready to rule.Here is a simple explanation of how this works. An internal combustion engine runs on a mixture of air and fuel. However, the precise air and fuel ratio needed by an engine varies depending on infinitely variable conditions. With a carburettor, one can adjust the blend to within a zone where the engine gets its approximate `fix.' However, making rapid changes to the mixture to suit every possible riding situation is well nigh impossible, prohibitively expensive and awfully complicated. EFI eliminates the carburettor and simplifies the game, while also offering lightning quick, and really precise metering.In an EFI-equipped bike, fuel is stored in the conventional manner within the motorcycle tank. From here, a pump sucks up the precious fluid and force-feeds it to an injector. A regulating system works hard to ensure that a constant, predetermined pressure is always on hand for the injector. Fuel injection relies on a batch of inputs from various sensors that supply their information to a central brain - the electronic control unit or ECU. Throttle position, airflow, engine temperature, intake air temperature, intake pressure, and engine speed are a few common factors taken into account by the ECU. Guided by these sensors, the ECU decides the precise fuel ratio needed by the engine for any given condition and orders the injector to deliver the same.The fuel injector itself is a valve capable of opening or shutting within the blink of an eye. The actual opening and shutting is performed by an electromagnet. When activated, pressure forces fuel to be spurted through a narrow orifice, so designed to atomise fuel into a fine spray that is easily combusted. This fuel mist is delivered into the intake manifold, ready to be sucked past the intake valve/s by the cylinder vacuum. Fuel amount offered is directly controlled by the period the fuel injector is kept open by the ECU. Most EFI systems incorporate safety cut-offs that kick in when they sense their engine has died or tilted beyond a safe limit - in the event of a crash. At these moments, the fuel pump immediately shuts down its supply. EFI negates the need for a manual choke, or riding with the choke on till engine operation temperature is obtained. It manages this via the ECU delivering a richer cocktail to the cylinder when the engine is cold, thus allowing hassle-free starts and glitch-free riding during the first few kilometres of the day. Carburettors are simply no match for an EFI system and Indian bikes will do well to switch to the latter. One added negative carb effect is that air needs to pass through the bottleneck in a venturi at all times. At high engine speeds, this sometimes limits the amount of air that can be shovelled through. EFI-equipped engines do not have to deal with this, as the air channel does not need to have any restriction. Greener emissions, higher and smoother power output and better fuel economy are all benefits to be allied with electronic fuel injection - the road ends for the carburettor here, long live fuel injection. RISHAD COOPER





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