What is an ignition distributor and what does it do?

1. What is a Distributor?
What is an ignition distributor and how does it work?
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2. Ignition
Distributor
Layout
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3. What is an Ignition Distributor?
• The ignition distributor is a crucial electrical
component in any car engine.
– The distributor carries out several different functions.
• The first and foremost responsibility of the ignition
distributor is to distribute the high voltage from the ignition
coil to the appropriate cylinder. The voltage is distributed
with help from the cap and rotor mechanism. The coil is
attached to the rotor, which spins inside the cap. The rotor
spins inside the distributor passing each contact for each
corresponding cylinder. When the rotor spins past one of the
contacts it distributes an electrical pulse from the coil. The
pulse continues down the spark plug wire to the spark plug
of the respective cylinder.
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4. Ignition Distributor Problems
• Cap and rotors are a common problem in most
vehicles. They begin to wear down over time from
spinning and passing the electric charge to the
cylinders.
• It is important when you are having your engine
serviced to have your mechanic inspect your ignition
distributor to make sure that is in good working
condition.
• Spark plug wires will also wear down over time, losing
their insulation. Problems with your ignition distributor
can cause all sorts of engine problems so it must be
replaced with a quality part as soon as possible.
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5. How Does a Distributor Work?
• The distributor handles several jobs. Its first job is to distribute the
high voltage from the coil to the correct cylinder. This is done by the
cap and rotor. The coil is connected to the rotor, which spins inside
the cap. The rotor spins past a series of contacts, one contact per
cylinder. As the tip of the rotor passes each contact, a high-voltage
pulse comes from the coil. The pulse arcs across the small gap
between the rotor and the contact (they don't actually touch) and
then continues down the spark-plug wire to the spark plug on the
appropriate cylinder. When you do a tune-up, one of the things you
replace on your engine is the cap and rotor -- these eventually wear
out because of the arcing. Also, the spark-plug wires eventually
wear out and lose some of their electrical insulation. This can be
the cause of some very mysterious engine problems.
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6. How Does a Distributor Work?
• Older distributors with breaker points have another section in the bottom
half of the distributor -- this section does the job of breaking the current
to the coil. The ground side of the coil is connected to the breaker points.
• A cam in the center of the distributor pushes a lever connected to one of
the points. Whenever the cam pushes the lever, it opens the points. This
causes the coil to suddenly lose its ground, generating a high-voltage
pulse.
• The points also control the timing of the spark. They may have a vacuum
advance or a centrifugal advance. These mechanisms advance the timing
in proportion to engine load or engine speed.
• Spark timing is so critical to an engine's performance that most cars don't
use points. Instead, they use a sensor that tells the engine control unit
(ECU) the exact position of the pistons. The engine computer then controls
a transistor that opens and closes the current to the coil.
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7. Ignition Timing
• The point at which the spark fires and ignites the mixture is critical to
ensure maximum torque output.
• Too early and the piston, which is compressing the air/fuel charge, will
meet gas expanding from the explosion causing excessive pressures.
• Too late and there will be a waste of compression and hence output.
• The trick is to find the optimum point to fire the mixture. This is typically
at the point on the torque curve called 'mean best torque' and is the
maximum torque output, against varied timing.
• Typically, the spark is fired 10-30 degrees before the piston reaches the
"top dead center" (TDC), the very top of its travel, The spark advance will
increase with the engine speed, because the mixture will burn at roughly
the same rate, irrespective of the engine speed and therefore needs to be
ignited earlier to achieve maximum pressure at the same point in the
engine cycle.
source: http://www.buyautoparts.com/howto/ignition-timing.htm

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9. What is a Distributor?
The End
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