Carburator Vs Fuel-Injection – Fuel Systems Explained


New bikes are being launched regularly in India. This year saw the launch of many exciting bikes from various manufacturers. Bikes such as the Bajaj Pulsar RS200, KTM RC200, Honda CBR 650F, Benelli TNT 300, Benelli TNT 600i etc. were all launched this year. All these bikes deliver exciting performance and are very appealing for motorcycle enthusiasts across the nation. What do they all have in common though? They are all equipped with a fuel-injector rather than a carburetor. What we are seeing here is the dawn of a new era where the carburetor is slowly being supplanted by the fuel-injector.


What is a Carburetor?

Fuel Systems Explained - Carburator

In a nutshell a carburetor is a device that helps in mixing air and fuel in the proper ratio in order to deliver the right mixture to the combustion chamber. Air to fuel ratio varies between 12:1 and 14.7:1. The 12:1 mixture is called a rich mixture which is necessary for starting and acceleration. The lean mixture is required for cruising speeds. Based on the position of the throttle valve (inside the carburetor), lean or rich mixture is sent to the combustion chamber. There, the charge (A/F mixture) is ignited by a spark plug and combustion commences.


What is a Fuel-Injector?

Fuel Systems Explained – Fuel-Injection

A fuel-injector is a device controlled by the ECU (Electronic Control unit) that delivers the correct air-fuel mixture to the combustion chamber. A number of sensors monitor parameters like combustion chamber temperature, oxygen content, exhaust gas temperature etc. Based on inputs from there sensors, the injector delivers the necessary air-fuel mixture to the combustion chamber by using pre-set maps stored in the ECU. The use of a pressure pumps allows for high injection pressures which in turn result in more complete combustion, thereby reducing emissions.


The rise and fall of the carburetor

As motorcycles started to be produced at an unprecedented rate, the demand for carburetors was at an all-time high. The principle of operation was fairly simple and it was very cost effective to produce. The use of electronics of bikes was slightly complicated and not very trustworthy. A fuel-injected bike those days also refused to deliver the zest one had come to experience on a carbureted bike. The fuel-injector required the use of sophisticated sensors and pressure pumps which usually shot up cost of production. Also, it was cheaper to adjust the carburetor than to change fuel maps on the ECU (for injectors). To say that the fuel-injected bikes develop more horsepower is also not true as some of the powerful bikes in history were carbureted.

As a result carburetors were undisputed for a long period of time. Why, then, are carburetors becoming obsolete? Why are manufacturers shifting towards a technology which increases costs?


Carburetor vs. Planet Earth

The age of the fuel-injector began at a time when people started to realise that a carburetor is not that great for planet earth. Carburetors or Carbs are not very precise and depend on atmospheric pressure. Too lean or too rich mixture entering the combustion chamber will result in poor combustion which in turn churns out Carbon monoxide and oxides of Nitrogen into the atmosphere. Also when the bike is not running, fuel stored in the carburetor bowl tends to evaporate which results in unburnt hydrocarbons being emitted into the atmosphere.

The fuel-injector, with new developments in technology, is very accurate. It can precisely vary the amount of fuel and air entering the combustion chamber according to different requirements like idling, acceleration, cruising etc., based on throttle input. As a result the quality of combustion is much better resulting in fewer harmful emissions. When it is combined with a catalytic converter, the emissions are reduced by a large margin. The use of fuel-injector also results in better atomisation and smoother ride.



So, is the Carburetor becoming irrelevant as every minute passes? Certainly not, especially in a volume focussed market like India where majority of bikes are sold only because they are affordable and cheap to run. Manufacturers in India just cannot accommodate for the high cost of the fuel-injectors. Hopefully, in the future, more stringent emission norms will force manufacturers to switch to an injector. Major manufacturers like Hero Motocorp, Yamaha and Bajaj have started to introduce fuel-injected bikes recently, which is a good sign. Even the iconic Royal Enfield has joined the fray by using fuel-injection on the Continental GT. However, in the short term, new bikes, especially in the commuter segment will continue to be equipped with carburetors.


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