Page 78 - Apprentice Manual_Neat

S2-Q48.) Which of the following determines the minimum temperature of the coolant when the engine is
running?

a.) *Thermostat
Correct. The thermostat will open and close to maintain the proper coolant temperature range.
b.) Radiator
The radiator is part of the cooling process. However, it cannot cool if the thermostat does not perform
its function.
c.) Fan
The fan is part of the process, but if the coolant is not allowed into the radiator by the thermostat,
cooling cannot occur.
d.) Timing
Not an appropriate response for the cooling system.

S2-Q49.) What is the purpose of an intercooler (after-cooler)?

a.) *Reduce intake charged air temperature
Correct. The intercooler is used to reduce intake charged air temperature.
b.) Mix intake air with intake fuel
Has nothing to do with intake air or fuel.
c.) Increase water pressure
Does not influence water pressure.
d.) Increase boost pressure
Does not affect boost pressure.

S2-Q50.) Excessive backpressure can cause which of the following?

a.) *High exhaust temperature and low power
Correct. Backpressure prevents the hot exhaust gasses from easily exiting the system. The
engine is forced to expend horsepower forcing exhaust out, thus increasing internal heat.
Wasted horsepower always ends up in the form of heat.
b.) Low exhaust temperature and high power
Backpressure prevents gasses from leaving the system. Preventing exhaust from leaving the system
would increase temperature. Power would be reduced as it is wasted trying to force the gasses out of
the system.
c.) High exhaust temperature and high power
While the exhaust temperature will rise, power will decrease since the engine must waste energy to
force the exhaust gasses past the increased backpressure.
d.) Low exhaust temperature and low power
While power will decrease from the inefficiency of having to force exhaust past the increased
backpressure, exhaust temperature will increase rather than decrease.

S2-Q51.) In a gas engine, high exhaust temperature can be caused by

a.) *Cylinder misfire
Correct response.
b.) Low boost
Incorrect.
c.) Under-speed
Incorrect.
d.) Light load
Incorrect.

EGSA Apprentice Certification Program Study Guide - Page 70