Transcript Manifolds - The Western New York Teacher Center / Overview

Manifolds
Intake Manifolds
Construction
Cast iron
Cast aluminum
Plastic
Composite
Plastic @ aluminum
Intake Manifolds
Plenum
Runners
Long – build low RPM torque
Short – maximum high RPM power
Intake Manifolds
Exhaust crossover
Coolant passages
Thermostat housing
Vacuum ports
EGR passages
EGR Valve
Exhaust gas recirculation
Used to reduce Nox (oxides of nitrogen)
The EGR system mixes spent exhaust
gasses with the fresh A/F mixture.
The inert exhaust gas displaces some of
the A/F mixture (5–10 %), thus reducing
combustion temperature.
High temperatures are the main cause of
Nox.
Carburetors and TBI
- The carb/TBI unit delivers an
air/fuel charge
- Most of the fuel in this charge will
evaporate by the time it reaches
the combustion chamber (up to
60%)
Carburetors and TBI
The remaining fuel droplets will be
carried to the combustion chamber at
high velocities (300 ft/sec).
Swirling aids in the atomization of fuel
Guide vanes
Abrupt bends
Rough inner walls
What about golf balls?
Carburetors and TBI
At low velocities (under 50 ft/sec) the
fuel droplets will separate from the
charge and form on the runners of the
manifold.
This is known as separation
A/F mixtures must be richer at idle to
compensate for this
Carburetors and TBI
Manifold runner cross-sections must
be large enough to flow sufficient
charge at high RPM but …
small enough to maintain a sufficient
velocity for fuel droplet suspension.
This is one reason why racing engines
have a high idle.
Carburetors and TBI
V-? Design
On a dual-plane or 180 degree manifold
one half of the carb. or TBI unit feeds
half of the cylinders.
Runners may be tuned
On a single-plane or 360 degree
manifold all cylinders are fed from one
open plenum.
The intake runners are therefore split into
two separate passages at different heights.
Open @ Closed Manifolds
Open – the bottom of the manifold is
separated from the lifter valley.
Benefit – the bottom of the manifold does
not contact the hot oil.
Cooler temp = denser charge
Open @ Closed Manifolds
Closed – the bottom of the manifold is
the top of the lifter valley.
Benefit – the bottom of the manifold
contacts the hot oil.
Better atomization of fuel at cold temps.
Coking may occur on a closed type
manifold if a heat shield is not used.
Thermo-barrier paints are also used.
Air-gap Manifold
Port Injection Manifolds
The fuel injector is located
approximately 3” from the intake
valve. Therefore:
Runners are for air flow only
Swirling is not as necessary
Plastic manifolds
Exhaust Manifolds
Generally cast iron
May be annealed (heat-treated)
May be tubular steel
Will generally house an o2 sensor
Cracks
Leaks
Headers
Runners
Collectors
Headers
Reduce restriction for better high
RPM power
Tuned headers – designed to
combine individual pulses into one
large pulse.
The pressure behind this pulse is lower
than atmospheric pressure.
Thus – a pulsing vacuum is present
called:
Scavenging
Headers
Low to medium RPM power and
torque
Long runners (34-38”)
Long collectors (12-15”)
High RPM power and torque
Increased diameter runners
Shorter runners and collectors
Benefits are measurable above
3500 RPM
Headers
Ceramic coating
Properly working headers should make
a rapping sound between 3500 to
5000 RPM.
Oil Pumps
Oil Pumps
All recent automotive oiling systems
are of a full-pressure design.
Typically driven by the
Camshaft
Distributor shaft (one-half engine speed)
Crankshaft (full engine speed)
Oil Pumps
All production oil pumps are positive
displacement pumps.
All oil that enters must exit
May be gear or rotor type.
Pumps are sized so that
approximately 10psi of pressure is
available at idle.
Pressure increases by approx. 10psi per
1000 rpm
Gear-Type Oil Pump
Rotor-Type Oil Pump
Oil Pumps
The oil pump is the only component of
an oiling system that receives
unfiltered oil.
On all oiling systems oil exiting the
pump will feed directly into the oil
filter.
The screen on the pickup is the only
method of debris stoppage.
Oil Pumps
Oil pump pick-up screens utilize metal
covers to prevent cavitation
(aeration).
Cavitation is caused by
Oil being exited out of the pump faster than
it can push it.
Air being sucked into the pump via a sudden
stop.
Oil Pressure Regulation
All full-pressure oiling systems utilize
a pressure relief valve
Generally spring regulated
The higher the spring tension the greater
the oil pressure
Excessive oil is bled back into the inlet side
of the pump.
Oil Pressure Regulation
3 to 6 gallons of oil per minute are
required to properly lubricate an
engine.
Excessive oil pressure does not
lubricate an engine better and
requires more horse-power to
maintain.
Oil Pressure
Effected by:
Oil viscosity
Engine/oil temperature
Engine integrity
Excessive bearing clearances.
Oil pump integrity
Excessive gear/cover/housing clearances.