Carburettor
is here to stay
By H. Kishie
Singh
WE are all very familiar with
carburettors. They have been around since the first
internal combustion engine fired into life.
"Fired" is the
correct word. The whole point of the internal combustion
engine is to create an explosion, which generates energy,
used to drive the car.
The purpose of the
carburettor is to feed a mixture of fuel (mostly petrol,
as diesel engines do not have carburettors) and air into
the cylinder. In the cylinder head there is a spark plug
that causes the explosion, and which in turn
pushes the piston down. Liquid petrol is fed into the
carburettor and exits as a fine spray. The liquid petrol
turns gaseous, thanks to the Venturi effect.
Earlier carburettors
were the only way to feed fuel to the cylinder. Now, fuel
is injected directly into the cylinder head to be fired.
Petrol is fed via a nozzle and it exits in a fine gaseous
spray. This is called fuel injection. It has been around
a long time but only now is it finding favour with the
manufacturers of hi-tech engines.
Originally, just one
nozzle or injector was used, and it was referred to as
the single point fuel injection. Improvements through
exhaustive R & D, have led to the mulitipoint fuel
injection (MPFI), which seems to be the new norm.
So is the carburettor on
the way out? Could be. It is claimed that the MPEI
provides greater efficiency in terms of fuel combustion,
and controlling pollution. A 1000cc engine with the MPFI
gives about 20 km per litre, manufacturers claim. It also
needs little or no maintenance. This plus point could
also be its weakest link. The quality of fuel is all
important to make the injectors work at full efficiency.
The injectors are
electrically controlled and monitor the precise amount of
fuel-air mixture. This is the reason for the efficiency.
There is no wastage.
In the naturally
aspirated engine, the mixture is set. It
stays the same even when the engine is hot, cold or warm.
This causes much wastage of fuel. The manufacturers
realised this and were constantly on the lookout for a
way to improve the carburettor.
The MPFI evolved. The
fuel-air mixture is electronically monitored and the
mixture can be varied to always provide the perfect
mixture. This control unit is called the ECM (Electronic
control module.) Rather than have one carburettor feed
the cylinders with the MPFI, each cylinder head has its
own individual injector. The ECM monitors the engine
temperature, the amount of pressure on the accelerator,
the engine r.p.m. and it even varies the input of the
mixture. This, the manufacturers claim increases the fuel
efficiency, increases engine life, so that it hardly
needs maintenance. In short, it stretches the rupee in
every direction.
However, carburettors,
which are undoubtedly the hardier lot, also hardly need
any maintenance.
Carburettors
manufactured in the 80s and 90s were already
100 years old but worked perfectly.
I have a carburettor on
my Gypsy which in 200,000 km of driving has had to be
opened twice. That counts as zero maintenance.
Though the MPFI is going
to be the next wave, the carburettor is here to stay.
Happy motoring!
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