CAE Vehicle Dynamics & Powertrain 3 — Questions and Answers
Question 1: What is the primary advantage of a continuously variable transmission (CVT) over a conventional stepped automatic?
- Higher torque capacity for towing applications
- Ability to keep the engine at its most efficient RPM across a range of vehicle speeds (Correct answer)
- Faster gear changes during wide-open throttle acceleration
- Better fuel economy specifically at high vehicle speeds above 70 mph
Correct answer: Ability to keep the engine at its most efficient RPM across a range of vehicle speeds
A CVT uses a continuously adjustable ratio to hold the engine in its peak efficiency band regardless of vehicle speed, improving overall fuel economy.
Question 2: How does increasing front anti-roll bar stiffness affect vehicle handling balance?
- Increases understeer tendency by reducing front lateral load transfer
- Increases understeer tendency by increasing front lateral load transfer (Correct answer)
- Increases oversteer tendency by reducing rear lateral load transfer
- Has no effect on understeer/oversteer balance, only ride quality
Correct answer: Increases understeer tendency by increasing front lateral load transfer
A stiffer front anti-roll bar transfers more lateral load to the outer front tire, reducing front cornering grip and promoting understeer.
Question 3: In a dual-clutch transmission (DCT), how are odd and even gear ratios typically organized?
- Odd gears on the outer clutch pack, even gears on the inner clutch pack with separate input shafts (Correct answer)
- Odd and even gears share one clutch but alternate synchronizer engagement
- Odd gears drive the front axle and even gears drive the rear axle
- Odd gears are wet-clutch and even gears are dry-clutch for efficiency
Correct answer: Odd gears on the outer clutch pack, even gears on the inner clutch pack with separate input shafts
A DCT has two concentric input shafts — one for odd gears and one for even gears — each with its own clutch, enabling pre-selection and near-instantaneous shifts.
Question 4: What is 'camber thrust' in tire mechanics?
- The additional drag force generated when a tire runs at negative camber
- The lateral force a tire generates due to camber angle, independent of slip angle (Correct answer)
- The vertical load increase on the outer tire during high-speed cornering
- The tendency of a cambered tire to wear the inner tread edge faster
Correct answer: The lateral force a tire generates due to camber angle, independent of slip angle
Camber thrust is a lateral force produced by a tilted tire trying to roll in a circle, adding to or subtracting from cornering force depending on camber direction.
Question 5: Which condition does a vehicle's 'scrub radius' most directly influence?
- Ride frequency and body roll moment arm
- Steering feel and torque steer sensitivity under braking or acceleration (Correct answer)
- Maximum lateral acceleration before tire saturation
- Camber gain through suspension travel
Correct answer: Steering feel and torque steer sensitivity under braking or acceleration
Scrub radius is the offset between the steering axis and the tire contact patch center; a large scrub radius amplifies drivetrain and braking forces into the steering column.
Question 6: In a four-wheel-drive system, what is the role of the transfer case?
- Splits engine torque between the front and rear driveshafts and provides low-range gearing (Correct answer)
- Converts transmission output from manual to automatic shifting modes
- Regulates differential lock engagement via electro-hydraulic clutches only
- Acts as the final drive reduction for the rear axle in 4WD mode
Correct answer: Splits engine torque between the front and rear driveshafts and provides low-range gearing
The transfer case divides torque between front and rear axles and typically offers a low-range gear reduction for off-road or high-torque situations.
Question 7: What does a positive 'ackermann angle' geometry intend to achieve during low-speed cornering?
- Equal slip angles on all four tires for maximum lateral grip
- Inner front wheel steers at a greater angle than the outer to reduce tire scrub (Correct answer)
- Outer front wheel steers at a greater angle to compensate for body roll
- Both front wheels steer at identical angles to maintain parallel tracking
Correct answer: Inner front wheel steers at a greater angle than the outer to reduce tire scrub
Ackermann geometry angles the inner wheel more sharply so both front tires trace concentric arcs around the same turning center, minimizing scrub at low speeds.
CAE Vehicle Dynamics & Powertrain 3
What is the primary advantage of a continuously variable transmission (CVT) over a conventional stepped automatic?