After bs4 euro 4 standard applied the ignition system plays a vital role for achieving pollution norms there are basically two engines petrol and diesel for operation and power generation .
In a petrol engine ignition system, a sparkplug is present on the top of the clynder head which ignites the charge i.e. a propotional mixture of petrol and air, when compressed by the piston head in the clynder resulting in ignition
whereas
In a diesel engine ignition system, a fuel injector is present on the top of the clynder head which sprays diesel on highly compressed air done by the piston head in the clynder which reaches temperatures resulting in ignition.