There are two types of carburetors: fixed choke and constant depression, the first type, fixed choke carburetors, makes the varying air pressure in the venture alter the fuel flow; this is the common downdraft carburetor found on American and most Japanese cars. The other type, the constant depression carburetors vary the airflow to change the fuel jet opening witch in turn altars the fuel flow. A vacuumed operated piston connected to a tapered needle, which slides inside the fuel jet, does this. The most common variable choke (constant depression) type carburetor is the side draft SU carburetor, which was simple in principle to adjust and maintain. This rose to a position of domination in the UK car market for that reason. Other similar designs are used on some European and a few Japanese automobiles.
Although the differences between the two types of carburetors are extensive there main function remains, they need to measure the airflow of the engine at any time, and then deliver the correct amount of fuel to keep the fuel/air mixture perfect and then mix the fuel and air evenly. A carburetor must provide the proper fuel/air mixture under a wide variety of different circumstances and engine speed range, random events that will affect the performance of the carburetor can be things like acceleration and cold start, waiting at a red light etc. This will be hard to do when you on top of this will need to maintain as low rates of exhaust emissions as humanly possibly for a poor carburetor.
To function correctly under all these conditions, most carburetors contain a complex set of mechanisms to support several different operating modes, called circuits.
You see, if the car has electronic controlled injection intake instead of a carburetor it will automatically adjust the intake according to previously programmed numbers and algorithms provided by the manufacturer. A carburetor on the other hand will usually not have any computer components, thus making the fuel/air mixture controlling purely mechanical. Also an injection intake will separate the air from the fuel allowing it to inject them independently from each other, the carburetor will accomplish both simultaneously as the throttle is opened.
An other difference between a carburetor and an injection is the way it is utilized when cold starting an engine, when the engine is cold, fuel vaporizes less readily and tends to condense on the walls of the intake manifold, starving the cylinders of fuel and making the engine difficult to start; thus, a richer mixture (more fuel to air) is required to start and run the engine until it warms up. In an injection engine a computer will control this automatically, but again the carburetor has to do this manually, therefore you will see a choke on a carbureted car and usually not in an injection based car.
Bath Vanities Wholesale Immediately
No comments:
Post a Comment