Engine performance Exam 1 Questions and Answers 100% Pass

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Engine performance Exam 1 Questions and Answers 100% Pass All overhead valve engines ________. ✔✔Have the overhead valves in the head An SOHC V8 engine has how many camshafts? ✔✔Two Torque ... is expressed in units of ________. ✔✔pound-feet Horsepower is expressed in units of ________. ✔✔foots per pound A normally aspirated automobile engine loses about ________ power per 1000 feet of altitude. ✔✔3% One cylinder of an automotive four-stroke cycle engine completes a cycle every ________. ✔✔720 degrees How many rotations of the crankshaft are required to complete each stroke of a four-stroke cycle engine? ✔✔one-half A rotating force is called ________. ✔✔Torque Technician A says that the crankshaft determines the stroke of an engine. Technician B says that the length of the connecting rod determines the stroke of an engine. Which technician is correct? ✔✔Tech A crankshaft Which component is NOT needed in a typical overhead cam engine? ✔✔pushrod Technician A says that a typical DOHC V6 engine uses two camshafts. Technician B says that overhead cam engines generally can run at higher rotational speeds than overhead valve engines. Which technician is correct? ✔✔Tech B overhead cam engines Which of the following is the most correct statement about the direction of engine rotation? ✔✔Most engines rotate clockwise as viewed from the front of the engine. The following statements are all correct EXCEPT ________ ✔✔Torque always results in movement Technician A says that changing connecting rod length changes engine stroke. Technician B says that changing connecting rod length changes the position of the piston in the cylinder. Which technician is correct? ✔✔Tech B Changes position on the piston All of these are correct EXCEPT ________ ✔✔Engines produce higher horsepower at higher altitude. The following statements are all correct EXCEPT ________ ✔✔Torque always results in movement. How many degrees of CRANKSHAFT rotation are needed to complete the four stroke combustion cycle? ✔✔720 How many degrees of CRANKSHAFT rotation are required for a piston to travel from TDC to BDC and return to TDC? ✔✔360 Winter blend gasoline ________. ✔✔Can cause engine driveability problems if used during warm weather Vaporizes more easily than summer blend gasoline Has a higher RVP Vapor lock can occur ________. ✔✔If a fuel line is restricted As a result of excessive heat near fuel lines Technician A says that spark knock, ping, and detonation are different names for abnormal combustion. Technician B says that any abnormal combustion raises the temperature and pressure inside the combustion chamber and can cause severe engine damage. Which technician is correct? ✔✔Both abnormal combustion Technician A says that the research octane number is higher than the motor octane number. Technician B says that the octane rating posted on fuel pumps is an average of the two ratings. Which technician is correct? ✔✔Both Octane Technician A says that in going to high altitudes, engines produce lower power. Technician B says that most engine control systems can compensate the air-fuel mixture for changes in altitude. Which technician is correct ✔✔Both Altitude Which method of blending ethanol with gasoline is the most accurate? ✔✔inline What can be used to measure the alcohol content in gasoline? ✔✔Graduated cylinder Electronic Tester To avoid problems with the variation of gasoline, all government testing uses ________ as a fuel during testing procedures. ✔✔Indolene Avoid topping off the fuel tank because ________. ✔✔It can saturate the charcoal canister Adding up to 10% ethanol to gasoline can also increase the fuel's ________. ✔✔volitility Using ethanol-enhanced or reformulated gasoline can result in reduced fuel economy. T or F ✔✔True Which of these symptoms may be caused by excessive ethanol in the fuel? ✔✔Rough idle or stall E85 means that the fuel is made from ________. ✔✔85% ethanol, 15% gasoline Methanol is also called ________. ✔✔Methyl alcohol Methyl hydrate Wood alcohol Which alcohol is dangerous (toxic)? ✔✔Methanol Liquefied petroleum gas (LPG) is also called ________. ✔✔Propane Technician A says the stoichiometric ratio for gasoline is about 9.0:1. Technician B says the stoichiometric ratio for ethanol is about 9.0:1. Which technician is correct? ✔✔Tech B stoichiometric A flex-fuel vehicle has enhanced fuel system components that include all of these EXCEPT ________. ✔✔Low temperature resistant O-rings What color is diesel fuel dyed if it is for off-road use only? ✔✔red What rating of diesel fuel indicates how well a diesel engine will start? ✔✔cetane rating Ultra-low-sulfur diesel fuel has how much sulfur content? ✔✔15 PPM B-20 biodiesel has how much regular diesel fuel? ✔✔80% Most manufacturers of vehicles equipped with diesel engines allow what type of biodiesel? ✔✔B20 Which is true of biodiesel fuel? ✔✔Reduces hydrocarbon emissions Reduces particulate matter in emissions Reduces carbon monoxide emissions Emission controls on what model year vehicles require ultra-low sulfur diesel fuel? ✔✔2007 Which is true of biodiesel fuel? ✔✔It is more expensive than petrol diesel It can be used in standard diesel systems without modification Permanent antifreeze is mostly ________. ✔✔Ethylene glycol As the percentage of antifreeze in the coolant increases, ________. ✔✔The freeze point decreases (up to a point) A stuck open thermostat can cause ________. ✔✔Failure of a State emission test Lower fuel economy Increased exhaust emissions A water pump is a positive displacement-type pump. ✔✔false The weep hole on a water pump is located where? ✔✔Between the seal and the bearing Technician A says that a bleeder valve is located on many engines to allow air to escape when refilling the cooling system. Technician B says that a hose should be attached to the bleeder valve to allow any escaping coolant to be directed to a suitable container. Which technician is correct? ✔✔Both bleeder valve Which statement is true about thermostats? ✔✔The temperature marked on the thermostat is a temperature at which the thermostat should start to open. Used coolant should be ________. ✔✔recycled or disposed of properly. An engine fails to reach normal operating temperature. Which is the most likely fault? ✔✔Defective thermostat The normal operating temperature (coolant temperature) of an engine equipped with a 195 degree F thermostat is ✔✔195 degree to 215 degree F The procedure that should be used when refilling an empty cooling system includes ________. ✔✔Determine capacity, then fill the cooling system halfway with antifreeze and the rest of the way with water Low engine operating temperatures will cause all of the following EXCEPT ________ ✔✔Accumulation of water in oil. Cylinder wall wear. Rust formation. All of these are symptoms of low operating temperatures. Which statement is true regarding cooling systems? ✔✔Heat transfer explains how radiators work. When testing thermostats, technician A uses a pyrometer and says the engine side of the thermostat should be the hottest spot in the cooling system. Technician B says that incorrect ignition timing may be the cause of engine overheating. Which technician is correct? ✔✔Both techs pyrometer Technician A says that you must completely drain coolant before replacing the thermostat. Technician B says that a defective thermostat is always the cause of an engine not getting hot enough. Which technician is correct? ✔✔Tech B cause of engine not getting hot enough The intake manifold of a port fuel-injected engine ________. ✔✔contains air only Why are the EGR gasses cooled before entering the engine on some engines? ✔✔Cool exhaust gas is more effective at controlling NOx emissions. A heated air intake system is usually necessary for proper cold-engine driveability on ________. ✔✔Throttle body fuel injection systems Why do many port fuel injected engines use long intake runners? ✔✔To increase low RPM power The upper portion of a two part intake manifold is often called the ________. ✔✔plenum Technician A says that a cracked exhaust manifold can affect engine operation. Technician B says that a leaking lower intake manifold gasket could cause a vacuum leak. Which technician is correct? ✔✔Both techs exhaust manifold Technician A says that some intake manifolds are plastic. Technician B says that some intake manifolds are constructed in two parts or sections: upper and lower. Which technician is correct? ✔✔Intake manifolds Technician A says that header-type exhaust manifolds produce less back pressure than do most cast-iron exhaust manifolds. Technician B says that only cast-iron exhaust manifolds are used on production vehicles. Which technician is correct? ✔✔Tech A less back pressure Technician A says that the Helmholtz resonator is used to speed up incoming air into the intake manifold. Technician B says that the Helmholtz resonator is used to quieten intake noise. Which technician is correct? ✔✔Tech B Helmholtz All these are functions of the air intake system ✔✔Act as a flame arrester in case of backfire. Silence intake noise. Clean the air. Which statement is correct? Port fuel injected vehicles mix the fuel and air charge in the intake manifold. With port fuel injection, fuel is injected directly into the combustion chamber. Throttle body injected vehicles do not require heating of the intake air charge. ✔✔Port fuel injected vehicles mix the fuel and air charge in the intake manifold. Which statement is correct? Long intake runners are good for low-RPM torque. Some engines use a variable intake runner design to improve engine efficiency. Short intake runners are good for high-RPM horsepower ✔✔All statements are correct Which of the following is correct? Many exhaust systems are tuned to reduce noise and optimize flow. Exhaust manifolds must be able to slide on the cylinder head slightly as they expand due to high heat. Many exhaust systems have heat shields to protect the spark plugs and wires. ✔✔all statements are corrects exhaust Which of the following is correct? Corrosion forms in the exhaust system in the absence of moisture. One gallon of gasoline produces a gallon of moisture during complete combustion. Water will not harm the exhaust system. A small hole at one seam of a muffler means it is damaged and must be replaced. ✔✔One gallon of gasoline produces a gallon of moisture during complete combustion. All of the following statements are correct EXCEPT ________ Most mufflers have a larger outlet than inlet. Most mufflers have a larger inlet than outlet. Resonators resemble small mufflers and are used to further quieten exhaust system noise. Mufflers catch the high pressure air pulses from the exhaust system. ✔✔Most mufflers have a larger outlet than inlet. What sensor is usually located between the air cleaner and the throttle body? ✔✔MAF Variable valve timing can be found on which type of engine? ✔✔Cam-in-block DOHC SOHC To reduce oxides of nitrogen (NOx) exhaust emissions, which camshaft is varied? ✔✔Exhaust camshaft only To increase engine performance, which camshaft is varied? ✔✔Intake camshaft only What is the commanded pulse width of the camshaft phaser that results in the desired position? ✔✔50% What sensors are used by the PCM to determine the best position of the camshafts for maximum power and lowest possible exhaust emissions? ✔✔Crankshaft position (CKP) Camshaft position (CMP) Engine speed (RPM) How is the camshaft actuator controlled? ✔✔Pulse width modulated (PWM) signal If the engine oil is not changed regularly, what is the most likely fault that can occur to an engine equipped with variable valve timing (VVT)? ✔✔The filter screens on the actuator control valve become clogged How quickly can the rocker arms be switched from the low-speed camshaft profile to the highspeed camshaft profile on a Honda equipped with a VTEC system? ✔✔100 milliseconds Most variable camshaft systems use ________ to control camshaft position. ✔✔oil pressure On many variable displacement engines the cylinder deactivation is done by use of a(an) ________. ✔✔Two stage hydraulic lifter Boost pressure is generally measured in ________. ✔✔PSI Two types of superchargers include ________. ✔✔Roots type and centrifugal Which valve is used on a factory supercharger to limit boost? ✔✔A bypass valve How are most superchargers lubricated? ✔✔By an internal oil reservoir Two technicians are discussing the term "turbo lag." Technician A says that it refers to the delay between when the exhaust leaves the cylinder and when it contacts the turbine blades of the turbocharger. Technician B says that it refers to the delay in boost pressure that occurs when the throttle is first opened. Which technician is correct? ✔✔Both techs delay What is the purpose of an intercooler? ✔✔To reduce the temperature of the air entering the engine Which type of relief valve is used on a turbocharged engine is noisy (and awesome)? ✔✔BOV Dump valve Technician A says that a stuck-open wastegate can cause the engine to burn oil. Technician B says that a clogged PCV system can cause the engine to burn oil. Which technician is correct? ✔✔Tech B PCV systems What service operation is most important on engines equipped with a turbocharger? ✔✔Regular oil changes All of the following statements are correct EXCEPT ________ Higher compression engines usually require higher octane fuel. Higher compression engines are more efficient. Higher compression engines are less likely to produce NOx emissions. Higher compression engines can produce more power. ✔✔Higher compression engines are less likely to produce NOx emissions. Which of the following is correct? Increasing air pressure always increases its density. Naturally aspirated engines have more compression than forced induction engines. Naturally aspirated engines require higher octane fuel. Naturally aspirated engines use atmospheric pressure to force air into the combustion chamber. ✔✔Naturally aspirated engines use atmospheric pressure to force air into the combustion chamber. All of the following statements are correct EXCEPT ________ Supercharging often removes hot exhaust gasses to lower the cylinder head temperature. Supercharging uses an air pump to force air into the combustion chamber. Supercharging often results in high emissions during deceleration and idle. Supercharging allows for lower compression when the engine is not required to produce high power. ✔✔Supercharging often results in high emissions during deceleration and idle. Technician A says that the paper test could detect a burned valve. Technician B says that a grayish white stain could be a coolant leak. Which technician is correct? ✔✔Both techs grayish white stain Two technicians are discussing oil leaks. Technician A says that an oil leak can be found using a fluorescent dye in the oil with a black light to check for leaks. Technician B says that a white spray powder can be used to locate oil leaks. Which technician is correct? ✔✔Both tech oils leaks Which of the following is the least likely to cause an engine noise? ✔✔Vacuum leak A good engine should produce how much compression during a running (dynamic) compression test? ✔✔60-90 psi A smoothly operating engine depends on ________. ✔✔Equally compression among cylinders A good reading for a cylinder leakage test would be ________. ✔✔All cylinders below 20% leakage Technician A says that during a power balance test, the cylinder that causes the biggest RPM drop is the weak cylinder. Technician B says that if one spark plug wire is grounded out and the engine speed does not drop, a weak or dead cylinder is indicated. Which technician is correct? ✔✔Tech B spark plug wire grounded Cranking vacuum should be ________. ✔✔2.5 inches Hg or higher Technician A says that a leaking head gasket can be checked using a chemical tester. Technician B says that a leaking head gasket can be found using an exhaust analyzer. Which technician is correct? ✔✔Both tech head gasket leak Which of the following is a complaint related to engine problems? ✔✔Oil Consumption Smoke Misfire What does black exhaust smoke indicate? ✔✔Excessive fuel What does blue exhaust smoke indicate? ✔✔burning oil What does white smoke exhaust smoke indicate? ✔✔Coolant in combustion chamber Technician A checks for gasoline in the oil by holding a match to the dipstick. Technician B checks for water in the oil by dropping a small amount on the hot manifold to see if it bubbles. Which technician is correct? ✔✔Both techs checking oil Which noise is most noticeable at idle? ✔✔valve train noise Which of the following could result in low engine compression? ✔✔Damaged valve Cylinder head gasket Damaged piston or piston ring When preparing for a compression test, technician A disables the ignition system. Technician B only removes the spark plug for the cylinder he is testing. Which technician is correct? ✔✔Tech A preparing for a compression test How many compression strokes should be used during a compression test? ✔✔four When performing a cylinder leakage test, the following statements are all correct EXCEPT ________ Shop air should be applied through the spark plug hole. Bubbles in the coolant may indicate a defective head gasket. Shop air should be applied to the dipstick tube. Air heard escaping through the tailpipe may indicate a defective exhaust valve. ✔✔Shop air should be applied to the dipstick tube. While performing a cylinder leakage test, technician A says that 20% leakage is acceptable. Technician B says that a cylinder will show too much leakage if the piston is not at TDC on its compression stroke. Which technician is correct? ✔✔both tech cylinder leakage test A cylinder power balance test is performed. Cylinders 1, 2, and 3, all drop 175 RPM when disabled with a scan tool. Cylinder 4 drops 50 RPM when disabled. The following statements are all correct EXCEPT ________ This test could also be conducted by grounding the plug wire for each cylinder. Cylinder 4 is much stronger than 1, 2, and 3. There may be a mechanical problem with cylinder 4. Cylinder 4 is much weaker than 1, 2, and 3. ✔✔Cylinder 4 is much stronger than 1, 2, and 3. Technician A says that removing the plug wire from a spark plug while the engine is running could damage ignition system components. Technician B says that grounding a spark plug wire while the engine is running could damage ignition system components. Which technician is correct? ✔✔TECH A removing spark pug Normal engine vacuum at idle is ________. ✔✔17-21 in Hg Which of the following is NOT a cause of high exhaust back pressure? ✔✔Vacuum leak Exhaust back pressure of an engine running at idle should be ________. ✔✔Less than 1.5 PSI [Show More]

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