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What advantage do petrol engines have in terms of driving performance?
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Petrol engines can achieve higher RPMs and horsepower, providing better acceleration and driving dynamics.
How does the compression ratio differ between diesel and petrol engines?
Diesel engines have higher compression ratios (15:1 to 23:1), whereas petrol engines have lower compression ratios (11:1 to 14:1 for naturally aspirated and 8.5:1 to 10:1 for forced induction).
What is the thermal efficiency range of diesel engines?
Diesel engines have a thermal efficiency of 40-45%.
Describe the role of the spark plug in a petrol engine.
The spark plug ionizes gases with high voltage to create a spark, initiating the combustion of the air-fuel mixture.
What is one economic factor to consider when choosing between petrol and diesel engines?
Diesel engines are more expensive to produce and maintain, requiring significant mileage to offset the higher upfront costs.
Name one environmental concern associated with diesel engines.
Diesel engines emit more nitrogen oxides (NOx) and soot particles compared to petrol engines.
Why do diesel engines typically have lower RPMs compared to petrol engines?
Diesel engines have lower RPMs because of the need for stronger, heavier internals and longer strokes needed for their high compression ratios.
Why are modern diesel engines considered to be cleaner?
Modern diesel engines have complex emission controls such as particulate filters and diesel exhaust fluid (DEF) systems.
What are two common ignition systems in older and newer petrol vehicles?
Older vehicles use a distributor and igniter, while newer vehicles use distributorless ignition systems with coil packs or coil-on-plug systems.
What type of injection is almost always used in diesel engines?
Direct injection is almost always used in diesel engines.
In terms of emissions, which type of engine generally emits more CO2?
Petrol engines generally emit more CO2 compared to diesel engines.
How do the fuel injecting timings differ between petrol and diesel engines?
Petrol engines inject fuel during the intake stroke, while diesel engines inject fuel late in the compression stroke.
What key characteristic gives diesel engines higher torque compared to petrol engines?
The longer stroke and higher compression in diesel engines give them higher torque.
What are the two stages of combustion in diesel engines?
The two stages of combustion in diesel engines are the uncontrolled (premixed) combustion and the controlled (post-injection) combustion.
What is the primary difference in the ignition method between petrol and diesel engines?
Petrol engines use a spark plug for ignition, while diesel engines rely on air compression to ignite the fuel.
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