Question 1

Technician A says cross-flow heads improve engine breathing. Technician B says cross-flow heads inhibit engine breathing. Who is correct?

Accepted Answer

Technician A is correct because cross-flow heads, where the intake and exhaust are on opposite sides of the head, allow for better engine breathing by improving the flow of air/fuel mixture into the engine and exhaust gases out of the engine.

Question 2

Headers are exhaust manifolds made of steel tubing.

Accepted Answer

Headers are indeed a type of exhaust manifold made from individual steel tubes for each cylinder, designed to improve the flow of exhaust gases away from the engine.

Question 3

A straight through muffler has short pipes and baffles that cause the exhaust gases to move back and forth as they travel through the muffler.

Accepted Answer

A straight through muffler, also known as a glasspack or straight pipe, allows exhaust gases to flow directly through the center of the muffler with minimal obstruction, typically without causing the gases to move back and forth significantly.

Question 4

Technician A says restrictor plate racing involves blocking off some of the exhaust ports. Technician B says manifolds that flow air only can have sharper bends than those that flow air and fuel. Who is correct?

Accepted Answer

Technician B is correct because manifolds that only need to flow air can indeed have sharper bends compared to those that must flow both air and fuel, due to the risk of fuel pooling in the bends of the manifold. Restrictor plate racing actually involves limiting the air intake to the engine to reduce power, not blocking off exhaust ports as Technician A suggests.

Question 5

Cylinder heads are being discussed. Technician A says porting is when the size of a passageway is altered. Technician B says polishing smoothes the surface of the port. Who is right?

Accepted Answer

Both statements are correct. Porting involves altering the size and shape of the intake and exhaust ports to improve airflow, while polishing is done to smooth the surface of the ports to reduce resistance and further improve airflow efficiency.

Question 6

What is plenum?

Accepted Answer

The answer of What is plenum?...

Question 7

When a port has been designed for a particular engine, it remains in the computer's memory and can be duplicated using a ____ on future sets of heads.

Accepted Answer

A CNC machine can precisely replicate the design of a port from computer memory on future sets of heads, ensuring consistent and accurate production.

Question 8

Hemispherical combustion chambers restrict airflow because of shrouding.

Accepted Answer

The answer of Hemispherical combustion chambers restrict airflow because of...

Question 9

Technician A says high rpm performance can mean poor low rpm performance. Technician B says purchasing just a high performance manifold without matching components will probably hurt performance. Who is correct?

Accepted Answer

Both statements are correct. High rpm performance parts can indeed compromise low rpm performance because they are optimized for a different operating range. Similarly, installing a high performance manifold without upgrading other components to match can lead to suboptimal performance, as the engine's components need to work harmoniously for the best outcome.

Question 10

What is the formula for the CFM requirement at 100% volumetric efficiency?
Give an example.

Accepted Answer

The answer of What is the formula for the CFM...

Question 11

Newer engines with port fuel injection (PFI) require intake manifold heating.

Accepted Answer

Newer engines with port fuel injection (PFI) do not typically require intake manifold heating because the fuel is injected directly into the intake port or cylinder, allowing for better control of the air-fuel mixture and improved cold-start performance compared to older carbureted systems.

Question 12

Racing engines that operate at speeds above 14,000 rpm often use pneumatic valve closing mechanisms.

Accepted Answer

Pneumatic valve springs are used in high-speed racing engines to overcome the limitations of traditional metal springs, such as valve float at very high RPMs (above 14,000 rpm), by providing a more consistent closing force.

Question 13

As each valve opens and compresses its valve spring, another valve is closing, decreasing pressure as its spring re-extends. This is known as the ____ characteristic.

Accepted Answer

The answer of As each valve opens and compresses its...

Question 14

Exhaust manifolds are often made of ____ because of its ability to tolerate fast, severe temperature changes.

Accepted Answer

Cast iron is commonly used for exhaust manifolds due to its excellent ability to withstand rapid and extreme temperature changes without warping or cracking.

Question 15

What are the three styles of exhaust systems?

Accepted Answer

The answer of What are the three styles of exhaust...

Question 16

Technician A says press bending reduces the diameter of tubing. Technician B says a mandrel bender prevents changes in a tube's diameter during the bend. Who is correct?

Accepted Answer

Press bending can reduce the diameter of tubing, and a mandrel bender is designed to prevent changes in a tube's diameter during the bend.

Question 17

What is the meaning of the term, red line?

Accepted Answer

The answer of What is the meaning of the term,...

Question 18

Modern day engines can have _____ valves per cylinder.

Accepted Answer

Modern day engines can have two, three, or four valves per cylinder, depending on the design and purpose of the engine. This allows for improved airflow, fuel efficiency, and overall performance.

Question 19

Technician A says that when valve lift reaches 25% of the port opening, maximum airflow is achieved. Technician B says the more a spring is compressed to lift a valve, the more pressure it exerts resulting in increased reliability. Who is right?

Accepted Answer

Technician A is correct because maximum airflow is achieved when valve lift reaches 25% of the port opening.

Question 20

What is the purpose of a catalytic converter?

Accepted Answer

The answer of What is the purpose of a catalytic...

Quiz 17: Engine Breathing: Intake and Exhaust Systems