Automobile Engineering in ME
The compression ratio in petrol engine is kept less than in Diesel engine because

It is just customary to have less compression ratio in petrol engines
Higher or equivalent compression ratio in petrol engines is not possible due to pre-ignition
Less compression ratio gives better performance
It makes petrol engines lighter

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Automobile Engineering in ME
The fuel pump of a programmed fuel injection (PFI) system operate for two seconds when the ignition is turned to the start position to

Supplies a large amount of fuel and thereby creates a choke effect
Pressurise the fuel system before the engine is started
Enable the pump's fault diagnosis function to operate
Warm up and lubricate the pump

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