Overview on Diesel and Petrol Engine

The combustion systems of the petrol and diesel engine are totally different. While the former makes use of spark ignition, the latter uses compression ignition. Due to difference in compression ratios, cylinder pressure and combustion cycle, the performance characteristics of both the engines differ greatly, even if the final power output is the same. Therefore if the diesel car is driven in the same fashion as the petrol car the response of the car will be entirely different for equal capacity engines.

Engine Performance Characteristics:

It can be observed from the characteristic performance curves of petrol and diesel engines that...

The low-end torque of the diesel engine is lower than that of the petrol engine, at same engine speed. The maximum torque of the petrol engine is at higher rpm than that of the diesel engine. The response of the diesel engine to acceleration and deceleration will always be slightly sluggish than that of the petrol engine due to “Component Inertia” and the different combustion process.

Therefore, while driving a diesel car ensure that...

• While releasing the clutch pedal for marching from the stop position, give a little more acceleration than you would give to a petrol engine
• To avoid deceleration jerk, synchronise the clutch release with engine speed
• While shifting to higher gear, accelerate engine to higher rpm (3000 to 2500) to avoid jerks or stalling
• Shift to lower gear as soon as engine rpm drops to (2000 to 2200) rpm which is less than max. torque rpm (2500)

Apart from the above practice, the following are good habits to cultivate...

• Always start the car from halt, in the first gear
• Switch off the AC and all other accessories while starting from rest
• Do not ride the clutch or drive with half clutch, instead use parking brake if required on gradient
• Have engine properly tuned, particularly for anti-stall setting
• Maintain the engine and fuel system properly
• Maintain correct tyre pressure