SUPERCHARGER
VS
TURBOCHARGER
VOLUMETRIC EFFICIENCY
It is a measure of how well an engine breathes. It’s a comparison of an actual
volume of air-fuel mixture drawn into an engine to the theoretical maximum
volume that cold be drawn in. volumetric efficiency is expressed as a percentage.
If the engine takes in airflow volume slowly, a cylinder might fill to capacity. It
takes a definite amount of time for the airflow to pass through all the curves of
the intake manifold and valve port
Therefore, volumetric efficiency decreases as the engine speed increases due to the shorter
amount of time the cylinders to be filled with air during the intake stroke. At high speed, it may
drop as low as 50%.
The average stock gasoline engine never reaches 100% volumetric efficiency. A new engine is
about 85% efficient. A race engine usually has 95% or better volumetric efficiency. These figures
only apply to naturally aspirated engines. However, with either turbochargers or superchargers,
engines can easily achieve more than 100% volumetric efficiency.
Many vehicles are equipped with a turbocharger or supercharger to increase power.
WHAT IS FORCED INDUCTION?
Both a turbo and supercharger are forced
induction systems. They are designed to
literally force air into your engine. The more
air you can get into your engine, the more
power your car will make.
PURPOSE AND FUNCTION
The amount of force an air-fuel charge produces when it is ignited is largely a
function of the charge density. Charge density is a term used to define the
amount of air-fuel charge introduced into the cylinders. Density is the mass of a
substance in a given amount of space.
The greater the density of an air-fuel charge forced into a cylinder, the greater the
force it produces when ignited, and the greater the engine power.
An engine that uses atmospheric pressure for its intake charge is called a
naturally (normally) aspirated engine. A better way to increase air
density is to use some type of air pump such as a turbocharger or
supercharger.
When air is pumped into the cylinder, the combustion chamber receives
an increase of air pressure known as boost, and can be measured in:
• Pounds per square inch (PSI)
• Atmospheres (ATM) ( 1 atmospheric is 14.7 PSI )
• Bars ( 1 bar is 14.7 PSI )
ADVANTAGES AND DISADVANTAGES
Advantages: Disadvantages:
Easier maintenance Lower efficiency
Lower production and development Lower power-to-weight ratio
costs
Small potential for tuning
Higher reliability (less separate
parts) Greater power loss at higher
elevation (lower air pressure)
Direct throttle response (no turbo compared to forced induction
lag) counterparts
THE AMOUNT OF NATURALLY ASPIRATED ENGINE
DEPENDS ON:
The amount of air inducted into the cylinder
Extent utilization of inducted air
The speed of engine
Quantity of fuel admitted and it’s combustion characteristics
Thermal efficiency engine
SUPERCHARGERS
A supercharger is an engine-driven air pump that supplies more
than the normal amount of air into the intake manifold and boosts
engine torque and power. A supercharger provides an instantaneous
increase in power with out any delay.
It is an air pump mechanically driven by the engine itself. Gears,
shafts, chains, or belts from the crankshaft can all be used to turn
the pump. This means that the air pump or supercharger pumps air
in direct relation to engine speed.
PRINCIPLES OF WORKING
More fuel + More air + Bigger explosion + Greater horsepower
But, we can not simply pump more fuel into an engine. The chemically correct
mixture ( 14 : 1 :: Air : Fuel ) – is an essential for an engine to operate perfectly.
Thus superchargers provides more air by compressing air above atmospheric
pressure, hence providing more fuel into the charge and would make for a more
powerful explosion.
Thus, increased power, Torque, and speed is achieved.
TYPES OF SUPERCHARGER
( BASICALLY MAIN TYPES OF SUPERCHARGERS )
1 Roots Types
2 Centrifugal Types
3 Screw Types
ROOTS SUPERCHARGER
It consist of two
cylindrically shaped
lobes in opposite
direction in a common
housing
Air enters the space in
between the rotor lobes
at inlet and is carried
around the rotor to
discharge port
CENTRIFUGAL SUPERCHARGER
It consist of an impeller which
rotates in counter clockwise
direction
The air enters the hub of the
impeller axially and is turned
radially in radial vanes
The air leaves the impeller at
high speed but low pressure.
A diffuser converts the high-
speed, low-pressure air to low-
speed , high pressure air.
TWIN-SCREW SUPERCHARGER
It contains a set of worm gears.
The air enters in a supercharger through
the top rear and is compressed between
the rotors.
The male rotor rotates in clockwise
direction while the female rotates in
counter-clockwise direction and
compresses air between them.
Once the air is screwed and compressed
the full length of the rotors it remains in
compressed state between the rotors
until the engine demands the boosted air.
DRIVES USED IN SUPERCHARGER
Mechanical :
Belt
Gear Drive
Chain Drive
Other :
Electric motor
Advantages :
Increased Power
No lag – Consistent power delivery
Generally better throttle response
No special procedures or extra maintenance
Easier to install than turbochargers
disadvantages :
Consume a lot of power from the engine (therefore, not very efficient)
Increases the strain on the engine
Expensive
Noise
TURBOCHARGER
The major disadvantage of a supercharger is it takes some of the engine power to drive the unit .
In some installations, as much as 20% of the engine power is used by a mechanical supercharger.
A turbocharger uses the eat of the exhaust to power a turbine wheel and therefore does not
directly reduce the engine power.
A turbocharger is an exhaust-driven air pump consisting of a pair of turbine wheels, not unlike
pinwheels, on a single shaft. One turbine is positioned in the exhaust stream; when the engine
revs, the exhaust makes it spin. This turns the second turbine, which is part of the intake system
that directs air into the engine, and acts as a pump.
In order to develop boost, the engine must be working hard enough to produce significant
exhaust pressure to spin the turbocharger. This results in “turbo lag” — the engine does not get a
power boost at lower engine speeds, and it feels as if the car is hesitating instead of accelerating.
Newer, more technologically advanced cars have less turbo lag than older cars. The advantage to
using turbocharging to boost power is that when the turbo is active, the engine uses fuel,
whether it be gasoline or diesel.
PARTS OF A TURBOCHARGER
HOW A TURBOCHARGER WORKS
1. Cool air enters the engine's air intake and
heads towards the compressor.
2. The compressor fan helps to suck air in.
3. The compressor squeezes and heats up the
incoming air and blows it out again.
4. Hot, compressed air from the compressor
passes through the heat exchanger, which
cools it down.
5. Cooled, compressed air enters the cylinder's
air intake. The extra oxygen helps to burn
fuel in the cylinder at a faster rate.
6. Since the cylinder burns more fuel,
it produces energy more quickly and can
send more power to the wheels via
the piston, shafts, and gears.
7. Waste gas from the cylinder exits
through the exhaust outlet.
8. The hot exhaust gases blowing past
the turbine fan make it rotate at high
speed.
9. The spinning turbine is mounted on
the same shaft as the compressor
(shown here as a pale orange line). So,
as the turbine spins, the compressor
spins too.
10. The exhaust gas leaves the car,
wasting less energy than it would
otherwise.
TURBOCHARGER
TURBO CHARGER SIZE AND RESPONSE TIME
Turbocharger response time is directly related to the size of
the turbine and compressor wheels
Small wheels accelerate rapidly ; large wheels accelerate
slowly
While small wheels would seem to have an advantage over
larger ones , they might not have enough airflow capacity for
engine
To minimize turbo lag, the intake and exhaust breathing
capacities of an engine must be matched to the exhaust and
intake airflow capabilities of the turbocharger.
BOOST CONTROL
Wastegate
A turbocharger uses exhaust gasses to increase
boost, which causes the engine to make more
exhaust gases, which in turn increases the boost
from the turbocharger.
To prevent over boost and severe engine
damage, most turbo systems uses wastegate.
A wastegate is a valve similar to a door that can
be open and close.
The wastegate is a bypass valve at the exhaust
inlet to the turbine.
It allows all the exhaust into the turbine, or it
can route part of the exhaust past the turbine to
the exhaust system
TURBOCHARGER FAILURES
When turbochargers fails to function correctly, a drop power is noticed.
To restore proper operation, the turbocharger must be rebuilt, repair, or replace.
It is not possible to simply remove the turbocharger, seal any openings and still maintain decent
drivability.
MAINTENANCE / PROBLEMS
Lack of oil
Dirty oil
Mechanical damage of vane wheels
Wastegate control problems
Oil caking
TURBOCHARGER
OR
SUPERCHARGER?
