modification of carburetor
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Joined: Mar 2010
18-01-2011, 11:09 AM

This project and implimentation aims to maximize efficiency of petrol engine by modifying carburetor in design and functioning principle , actually carburetor is a device that blends air and fuel for an internal combustion engine.

Carburetor Principle

The carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure, and the higher its dynamic pressure. The throttle (accelerator) linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being pulled into the engine. The speed of this flow, and therefore its pressure, determines the amount of fuel drawn into the air stream

main thing to do ..
Transfer Slot Checking
Booster Balancing
Air-Bleed Sizing
Power Valve Matching
Idle Feed Relocation
and some customized setting to increase performance
Use Search at wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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16-02-2011, 11:11 PM

Please send more information regarding the carburetor modification.
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Joined: Nov 2012
08-11-2012, 01:17 PM

Modification of Carburetor

.pdf   Carburetor.pdf (Size: 91.49 KB / Downloads: 183)

One of the more commonly misunderstood systems on most motorcycles is its carburetor(s). Carburetors in
general are mysterious things to many, and when you start putting a bunch of them on a multi-cylinder
engine like most modern motorcycle manufacturers like to do, it simply adds to the confusion. Let's see if we
can clear up some of this stuff including that darn "rejetting" thing all our self-proclaimed "knowledgeable"
buddies are always talking about.
The basic function of a carburetor on a spark ignition engine is to mix the fuel with the incoming air in the
proper proportions so that the engine can then burn it efficiently. Most carburetors also control the speed of
the engine. They do this by throttling
the amount of air the engine sees. Contrast this with a typical diesel engine that has its speed controlled by
the amount of fuel injected into it, as it has no air throttle. (We'll also talk a little more about fuel injection
towards the end.)
But first off, we need to identify some of the basic elements of a carburetor as this helps explain how they
work. You need a minimum of three elements including a source of fuel, usually from a fuel bowl, a venturi
that we'll talk about in a moment, and a fuel-metering device called a jet. If we want to use the carburetor to
control the engine's speed, we'll also need some form of throttle to vary the amount of airflow going into the
Taking it one piece at a time, the fuel bowl does a couple of things. As stated, it provides a source of fuel.
But it does it in a very specific way. It keeps the air pressure over the fuel in the bowl at a normal outside
atmospheric level. That is the job of the fuel bowl vent and one of the carburetor's key elements. The next
item is the venturi, which is a portion of the carburetor's main air passage that momentarily narrows down.
Connecting the two is the fuel jet. Here's how it all works.
One of the Bernoulli clan, Daniel I think it was, discovered this neat effect that as you accelerate the flow of a
set volume of gas, air in this case, you decrease its relative pressure. Guess that's why they call it the
Bernoulli effect, huh!
So, how can we accelerate our air coming into the engine? As luck would have it, another guy with the name
of, you guessed it, Venturi, came along a bit after Bernoulli. This was Giovanni Battista Venturi and he
found out that if you took a passageway like a tube, and narrowed it down just a bit in the middle, the air
flowing through it would have to accelerate momentarily as it went through the narrowed down portion. It
would then return to its normal speed at the other side of the narrow potion. By the way, this is also a subtle
effect. Narrowed down too much and we've simply created a restriction to the airflow. But done just a little
and the air molecules have to speed up a little so the same amount of them can get through the smaller
passageway. They get to the other side where things open up again and they get to slow down and relax
once more.

Where CV carbs

get fooled and are tricky to work with is when changes are made to the air box/air filter system or large
changes to engine displacement and camshaft profiles. In addition to the usual main jet, needle and pilot jet
changes, some tuners change the rate of the slide return spring or modify the slide itself by adding extra air
bleed holes. But we've now made some major changes to the airflow characteristics of the engine and the
porting of the airflow that controls the slide may be way off. Long camshaft timing, characterized by long
duration opening specifications and lots of intake to exhaust timing overlap also means terrible airflow signal
at lower engine speeds. This means lousy carburetion no matter what kind we're using, but the CV carbs will
be particularly hard to set up properly.
So, if we're junking the airbox for some velocity stacks and separate K&N filters, installing that big-bore
cylinder kit and stuffing the largest camshaft we can find in there, we're probably going to have some
problems with our stock CV carbs. Chances are also good that we're not going to care all that much how the
engine responds at lower speeds. Now we're just looking for as much horsepower as we can get. Here our
slide carbs
will be the best bet. They will be dimensionally smaller for the same carburetion size and much easier to
tune. In addition to the usual main jet, pilot jet and needle changes, we can also play with the shape and size
of the slide's cutaway. Some of the best racing carbs also have replaceable venturi throats making them
adaptable to a wide variety of engine sizes and states of tune. You still need to be in the ballpark to begin
with, but it's a lot easier to get there with a slide carb.


So, what can we, the average backyard mechanic wannabe, do when it comes to making changes to our
carbs? First, if you have a modern new motorcycle, it should be pretty darn good just as it comes from the
factory. That is, if all the factory systems are still in place. And it's also legal. Making any modifications to the
motorcycle's engine or its ancillary systems is illegal in many areas for bikes registered and used on the

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