Sample Review Questions:
1.
Counterman A says front-wheel drive cars and minivans with transverse
(sideways) engines often have a flexible head pipe or coupling to
accommodate engine motions. Counterman B says the Y-pipe on a V6 or V8
engine connects the exhaust manifolds to the catalytic converter. Who’s
right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one
2. A “pre-catalyst” is usually located where?
a. Between the cylinder head and exhaust manifold
b. In or just behind the exhaust manifold
c. Just behind the catalytic converter
d. Between the converter and muffler
3. A “resonator” does what?
a. Helps reduce emissions
b. Helps dampen vibrations
c. Helps muffle noise
d. Helps reduce backpressure
4.
Counterman A says a “cat-back” replacement exhaust system usually
includes a new Y-pipe or head pipe, intermediate pipe, muffler and
tailpipe. Counterman B says other parts that may need to be replaced
when changing a muffler or pipe include clamps, hangars, gaskets and
heat shields. Who’s right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one
ANSWER KEY
1C, 2B, 3C, 4B
EXPLANATIONS:
1.
A transverse mounted engine in a FWD car or minivan does a fair amount
of forward and backward rocking, so the exhaust system must be able to
accommodate these motions. Some use a braided steel flex pipe between
the exhaust manifold and converter, while others use a flexible
spring-loaded connection at the head pipe or converter.
The Y-pipe
on a V6 or V8 engine routes the exhaust from both sides of the engine
into a common pipe that connects to the catalytic converter. Y-pipes
are not used on V6 and V8 engines with dual exhausts.
2. To
reduce cold-start emissions, some late-model vehicles have a small
pre-catalyst or “pup” converter mounted inside or just behind the
exhaust manifold(s). The pre-cat works the same as the main converter,
but heats up and reaches operating temperature much more quickly. This
also helps light off the main converter sooner, too.
3. Exhaust
systems often have more than one muffler. A secondary muffler, called a
resonator, may be located ahead or behind the main muffler to further
attenuate noise in the exhaust. The resonator is usually smaller and
less restrictive than the main muffler.
4. A cat-back system
includes all of the exhaust components aft of the converter, such as
the intermediate or crossover pipe, muffler, resonator (if used) and
tailpipe. It would not include a head pipe or Y-pipe, as these are
located ahead of the converter. Free-flowing aftermarket cat-back
systems are often used to reduce backpressure and improve power and
fuel economy.
When a muffler or resonator rusts out, the adjacent
exhaust pipes often have to be replaced, too. Replacing pipes requires
clamps for each end, or in some cases gaskets if the pipe connections
have bolt-together flanges (which are used on some import
applications). New gaskets would also be required if replacing a
cracked exhaust manifold. New hangers and/or heat shields would be
recommended if the original parts are in poor condition, broken or
missing. Loose or cracked heat shields can cause rattles. Missing
shield should be replaced to keep heat away from the floor of the
vehicle, or near fuel or brake lines.
Sections covered:
Automatic Transmission
Batteries
Brakes
Cooling System
Drivetrain
Emissions
Engine Mechanical Parts
Exhaust
Fuel System
HVAC
Gaskets
Ignition System
Manual Transmission
Suspension and Steering
Management