If you still believe RX100 is superior to pulsar’s and apache’s and trust the two stroke engines more than four stroke’s in a race, set your eye on Bajaj Auto. Bajaj may soon come with two stoke two wheeler again but this time with more efficiency. Bajaj recently introduced the GDi in its three wheelers and found that it increases the mileage and reduces the emissions. Indications are that an agreement has been finalised with Bosch of Germany for a GDI system in Bajaj bikes he Bosch relationship could logically extend to the company’s small car being planned in an alliance with Renault and Nissan.
The GDi for the autorickshaw is a Synerject (the joint venture between Orbital Corporation of Australia and Siemens VDO) system, which has now come into India with Chennai-based UCAL as the licensed supplier. Bajaj’s proven Digital Twin Spark Ignition may pave way for the much superior GDi technology atleast in smaller capacity bikes. In european markets, already there ar two wheelers powered by this technology. The Orbital system is used in motor scooters manufactured by Aprilia, Piaggio, Peugeot and Kymco. Let’s check out the GDi?
GDi – Gasoline Direct Injection, as the name implicates it means injecting the fuel directly into the cylinder. Two types of GDI are used in two-strokes: low-pressure air-assisted, and high pressure. When applied in two stroke engines, GDi makes remarkable improvement in mileage section. In conventional (carburetted) two-stroke engine exhaust port opens too early(before the completion of the stroke) and lets out the unburnt fuel charge. In direct injection technoogy the gasoline is injected via a common rail fuel line directly into the combustion chamber of the cylinder. The result is the only air comes from the crankcase(as opposed to the charge in conventional two stroke), and fuel is not injected until the piston rises and all ports are closed. This results gain in fuel efficiency and reduction in emission.
Rather than using high pressure injection to atomize the fuel charge in a manner similar to diesel injection, Orbital uses an air-assisted low-pressure direct fuel injection, combustion and engine management system: the Orbital Combustion Process (OCP) technology. With OCP, compressed air breaks up the fuel droplets. At light loads, the direct injection system allows engines to run very lean. Under high load conditions, the OCP system runs similar to a homogeneously charged engine, with good mixing of the fuel/air mixtures within the cylinder.
The cylinder head in a DI engine carries a fuel rail assembly which contains a fuel injector and a pressure regulator. Filtered fuel is supplied to the fuel rail assembly by an electric pump and filtered lubrication oil is through another. Fuel injector meters the fuel under regulated pressure and sends the fuel to the air injector. The air injector recieves the air compressed by the crank and injects this fine mist of air,fuel and lubricant into the combustion chamber. The result is more efficient atomisation which results in efficient combustion. The ECU(Electronic Control Unit) which is the brain of this system computes the speed and load desired from sensors. Crank postion sensor, throttle position sensor and engine temperature sensor sends data to the ECU. With those inputs, ECU determines quantity of fuel to be injected, timing of injection, metering of lubricant and timing of spark
Though the tech is not revolutionary and simple, it results in better combustion of fuel. Also, it is more practical and can be adapted even in the existing two stroke engine with few changes.