Manifolds

Intake Manifolds

ConstructionCast iron

Cast aluminum

Plastic

CompositePlastic @ aluminum

Intake Manifolds

Plenum

RunnersLong – 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 fuelGuide vanes

Abrupt bends

Rough inner wallsWhat 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 TBIV-? 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 ironMay be annealed (heat-treated)

May be tubular steel

Will generally house an o2 sensorCracks

Leaks

Headers

Runners

Collectors

Headers

Reduce restriction for better high RPM powerTuned 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 torqueLong runners (34-38”)

Long collectors (12-15”)

High RPM power and torqueIncreased diameter runners

Shorter runners and collectors

Benefits are measurable above 3500 RPM

HeadersCeramic 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 theCamshaft

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 byOil 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 integrityExcessive bearing clearances.

Oil pump integrity Excessive gear/cover/housing clearances.