Advantages of Four-Valve Engine and Variable Compression Ratio Engine

UNIT 25: VEHICLE SYSTEMS & TECHNOLOGY
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Task 1
Questions to decide
SI engine or CI engine
 Is the vehicle to have better fuel efficiency?
 Does the vehicle have an ignition system?
 Is better mileage needed? (Ananthakumar, Jayabal and Thirumal, 2017)
 What stability is needed in carrying heavy loads?
 Is more power needed?
Two- or four-stroke
 What is the cost of contruction?
 Which is lighter?
 What about the ease of starting the engine?
 What is the oil consumption rate?
 Which of the engines has more power strokes for every second revolution?
 Which of the engines is more noisy or louder?
 Which of the engines produce more heat requiring heavier systems of cooling?
 What is the power production of the engines?
 How about center of gravity of each of the engines, which has a lower value?
Naturally aspirated or supercharged
 Is rapid acceleration required?
 Is narrow or broad power band needed?
 Is power efficiency a consideration of the choice?

 Which of the engines produce less heat hence high energy efficiency?
 Does the engine need to have a good power to weight ratio?
Water- or air-cooled
 Which of the engines are smoother and more resistance to breakdowns?
 What is the ease of operation of either of the engines?
 Which of the engines can maintain a better control temperature?
 Is more power needed?
 Which of the engines produces less noise?
 What is the cost of maintaining either of the engines?
 Which of the engines is good with regard to power, cooling as well as efficiency?
 Which of the two machines will have more powerful as well as torque alongside more
mileage engines?
Task 2: Advantage of:
A four-valve engine over a two-valve one
A four stroke internal combustion engine needs the air fuel mixture within the chamber to
undergo proper burning to generate a good amount of power as well as deliver great fuel
efficiency (Jia et al., 2016). The valves enable entering of the air-fuel mixture to the combustion
chamber. An increase in the number of valves results in an increase in the air intake capacity and
hence in mathematical terms, breaking a large valve into two smaller ones of half radii would
lead to a 50% increase in the airflow to the engine.
Having four valves rather than two may be expensive hence in some instances, the manufacturers
use two valves for the inlet and instead just one for the exhaust for the purposes of cost saving.