Sun Jan 29 16:56:10 2006

TAC 	An acronym for thermostatically controlled air cleaner
TAC-AD 	Thermactor air cleaner-air diverter
TAC-BMS 	Thermactor air cleaner-bi-metallic sensor
TAC-CV 	Thermactor air cleaner-check valve
TAC-DV 	Thermactor air cleaner-delay valve
TAC-PVC 	Thermactor air cleaner-ported vacuum switch
TAC-RDV 	Thermactor air cleaner-reverse delay valve
TAC-RDVS 	Thermactor air cleaner-reverse delay valve single
TAC-TCV 	Thermactor air cleaner-thermal control valve
TAC-TS 	Thermactor air cleaner-temperature sensor
TAC-TSOV 	Thermactor air cleaner-temperature sensor override valve
TAC-TV 	Thermactor air cleaner-thermal vacuum valve
TAC-TVS 	Thermactor air cleaner-thermal vacuum switch
TAC-VCDV 	Thermactor air cleaner-vacuum control delay valve
TAC-VCV 	Thermactor air cleaner-vacuum control valve
TAC-VM 	Thermactor air cleaner-vacuum motor

Here's some additional smog info... found at:
	http://www.mirafiori.com/smog/specfiat.html
	(fiat - fix it again tony... very relevant to FSJs'. ;)

# AIS- Air Injection System- Air Injection defines a system that introduces
fresh air to the exhaust stream. This has been used in many ways, but the
primary reason is to help raise the exhaust temperatures, promoting continued
combustion of the exhaust gases as they leave the system. Air can be
introduced either by way of a belt-driven air pump, or by the natural vacuum
that occurs when hot, moving exhaust gases pass an open port. The latter style
is usually called reed valve or Pulse Air Injection. In early cars, a
thermactor system was used- This basically allowed the hot (partially
unburned) gases leaving the exhaust valves a fresh shot of air, causing them
to 're- burn' as they left the manifold. Heat was again a primary function in
later cars using catalysts, as the catalyst needs to reach operating
temperature before it an do its job (see Catalyst), and the fresh shot of
oxygen also helps the chemical reaction inside the catalyst. An important
note: Most air pumps use less than .5HP at peak load- the plumbing associated
with these systems can be a headache, but the actual performance losses are
minimal. Indeed, some long-term Fiat mechanics tout the air injection, saying
it keeps the exhaust valves cooler, prolonging the life of the engine. Make
your own judgment.

# Breather- The breather system seals crankcase blow-by gases and routes them
to the intake for combustion. Most cars use a vacuum operated PCV system to
accomplish this- Fiat, and some other European cars were the last to use a
passive breather system in their US-bound cars.

# CA- California certified car. These days, most cars are built to 50-State
specification, because most states have stringent emission control
regulations. In the past, some manufacturers had specific models built to pass
regulations for sale in California, because CA regulations were so much more
stringent at the time. Cars not built to California spec. were called Federal,
or 49-State cars. This was done primarily to save money in those US states
where extensive emissions control equipment was not required.

# Catalyst- An exhaust device that uses a chemical reaction to reduce harmful
exhaust emissions. See OC.

# Charcoal Canister- See EVAP

# Check Valve- A one-way valve, usually found in Air Injection systems.

# CO- Carbon Monoxide- Odorless, colorless and toxic, this gas is a major
byproduct of combustion.

# EGR- Exhaust Gas Recirculation- EGR is a system whereby a small amount of
exhaust gas is redirected to the intake stream, under certain load and
temperature conditions. This is not done to reburn the gas (as is widely
thought), but to lower overall combustion temperatures. Lower combustion
temperatures reduce the amount of NOX produced during the combustion process.

# EVAP- Evaporative fuel emission controls- Many systems exist, but the
concept is to reduce the amount of raw hydrocarbons that are emitted when an
open fuel tank 'perks' as its temperature, and density changes. Most systems
use a charcoal vapor canister to trap the vapors when the car is parked, and
slowly vent those vapors to the intake when the car is running.

# HC- Hydrocarbons- Basically the chemical term for unburnt fuel.

# NOX- Nitrous Oxides- A byproduct of high-temperature combustion, NOX is
produced when Oxygen, and Nitrogen present in the intake stream combine under
pressure, and heat. NOX is a major contributor to atmospheric problems
associated with smog.

# O2 Sensor- Device that converts oxygen content present in the exhaust stream
to a voltage signal, usually between 1.0-1.5 volts. This voltage signal is
used by the ECM to help determine mixture. O2 sensors need to reach operating
temperature before they start to operate, and do wear out over time. Fiats
used O2 sensors on the fuel-injected models, see your service manual for test
procedures.

# O2- Oxygen

# OC- Oxidizing Catalyst- The catalytic converter is a device that, under
relatively high heat (400 degrees+ F.) utilizes a chemical reaction to convert
Oxygen, Hydrocarbons and Carbon Monoxide into water vapor and Carbon Dioxide.
The catalyst is filled with a substrate of precious metals, usually platinum
and palladium, with the addition of rhodium in some cases- Early catalysts
have loose pellets inside them (some of which allow you to change the
substrate if you have access to new pellets), but later- style have a
honeycomb style 'brick' inside them. Most Fiats here have an early OC-
Carbureted cars had the original 3-bolt flange style Cat, and Fuel-Injected
cars got the 4-bolt flanged Cat.

# TAC- Thermostatic Air Cleaner - This system directs heated air (usually
picked up by a stove on the exhaust manifold) to the induction system to aid
in warm-up. Refer to your vacuum diagram. Most cars have a simple thermovalve
that inhibits vacuum when cold, allowing a vacuum-operated flapper valve on
the cold air side of the air cleaner to shut. When the car warms up, vacuum is
allowed to draw the flapper open, allowing fresh cold air to the air cleaner.
Some cars, (specifically pre-'79 carbureted Fiats) have a manual climactic
setting, allowing you to change the position of the air cleaner with the
season. This allows warm air all the time in one position, and cold in the
other.

# TPS- Throttle Position Sensor- Sends information (usually a resistance
figure through a potentiometer) to the ECM regarding throttle plate opening.

# TVS- Thermal Vacuum Switch- A favorite of Fiat, this device either closes
off or allows the flow of vacuum based on coolant temperature. Most often used
in spark control or EGR vacuum circuits, they go bad often.

# Vacuum Advance- Controls ignition timing based on manifold (or ported)
vacuum.

# Vacuum, Manifold- Vacuum source in manifold below throttle plate.

# Vacuum, Ported- Vacuum source in carburetor above throttle plate.

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