This set of Vehicle Dynamics Multiple Choice Questions & Answers (MCQs) focuses on “Engines in Power Limited Acceleration Performance”.
1. Which of the following has a flat torque curve?
a) Diesel Engine
b) Petrol Engine
c) CNG Engine
d) Electric Motors
View Answer
Explanation: Diesel engines have a relatively flat torque curve which sometimes rises slightly with decreasing engine speed. This has led to high torque rise at low speeds in heavy-duty engines when controlled by injection systems. Petrol and CNG engines have a torque curve that peaks mid-range. Electric motors used in electric vehicles can produce high torque at low rpm for a better “off-the-line” acceleration.
2. What is the first-order determinant of acceleration performance?
a) ratio of engine speed to engine power
b) ratio of engine torque to engine speed
c) ratio of the vehicle weight to engine speed
d) ratio of the engine power to the vehicle weight
View Answer
Explanation: High power engines produce more power hence more acceleration. But, higher vehicle weight decreases acceleration. Hence, it is often seen that trucks have lower acceleration compared to passenger cars even though their engine can produce higher power. The power to weight ratio of trucks is lower than cars.
3. What is the specific fuel consumption of most petrol engines?
a) 122 gram/kilowatt-hour
b) 244 gram/kilowatt-hour
c) 500 gram/kilowatt-hour
d) 800 gram/kilowatt-hour
View Answer
Explanation: Fuel economy of petrol engines is lower than diesel engines. This is due to the higher compression ratio in diesel engines. Thus the specific fuel consumption of petrol engines is 244 gram/kilowatt-hour whereas, it 122 gram/kilowatt-hour for diesel engines.
4. Tire traction is the source of propulsive power in a vehicle.
a) True
b) False
View Answer
Explanation: Engine is the source of propulsive power. Traction generated between the road and the tire is used to move the vehicle forward.
5. Diesel engines are fuel injected.
a) True
b) False
View Answer
Explanation: Diesel forms a non-homogeneous mixture with air. Diesel auto ignites and needs to be atomized at high pressure for efficient combustion. Hence, it is fuel injected.
6. Power and torque are related by _____
a) mass
b) length
c) linear speed
d) angular speed
View Answer
Explanation: Power and torque are related by angular speed. Power and force are related by linear speed. Magnitude wise, power is torque times angular speed or force times linear speed.
7. Engine speed is normally displayed in _____
a) rotation per minute
b) radian per second
c) rotation per hour
d) meter per second
View Answer
Explanation: Engine speeds in vehicles is normally displayed and measured in rotation per minute or rpm. Radians per second is used in analysis and calculation purposes as it is the SI unit. Meter per second is a unit for linear speed.
8. At high power requirement, what is the Air/Fuel ratio going into an engine cylinder generally?
a) Lean mixture
b) Stoichiometric mixture
c) Balanced mixture
d) Enriched mixture
View Answer
Explanation: At high power requirement, an enriched mixture, that is, more than 14.7:1 A/F ratio, which is the stoichiometric ratio, is required. More fuel needs to be burnt to produce more power. A lean mixture is used for during cruising mode.
9. Which of the following issue can reduce the propulsion power of the engine?
a) Tire imbalance
b) Steering misalignment
c) Lean air-fuel mixture
d) Low tire inflation pressure
View Answer
Explanation: A lean air-fuel mixture has more air compared to the stoichiometric ratio. Thus the power generated from the engine is reduced as less fuel is burnt. Tire imbalance, low tire inflation pressure, and steering misalignment all reduce the overall straight-line acceleration performance of the vehicle.
10. BSFC stands for _____
a) Brake Special Fuel Consumption
b) Brake Specific Fuel Consumption
c) Brand Specific Fuel Consumption
d) Brake Sudden Fuel Consumption
View Answer
Explanation: Brake Specific Fuel Consumption or BSFC is a measure of the fuel efficiency of an engine. It is represented as the weight of fuel consumed per unit time per unit power output.
Sanfoundry Global Education & Learning Series – Vehicle Dynamics.
To practice all areas of Vehicle Dynamics, here is complete set of Multiple Choice Questions and Answers.
