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Discussion in 'Mechanical | Automobile | Aeronautics' started by N.SACHIN, Jul 25, 2014.
Why is more power attained by a petrol engine than a diesel one?
It is due to the high compression ratio and burning temperatures, the diesel engines are more efficient. But the thing is that, it needs more space inside the combustion chamber of the engine cylinder. Whereas, a petrol engine needs a less space. But when we compare these two kinds of engines, a petrol engine consumes more fuel for the completion of a thermodynamic cycle, whereas the diesel engine takes less amount of fuel. And that's why a petrol engine attains more power than that of a diesel engine. But comparing to the amount of consumption of fuel, Diesel engines are always efficient.
Petrol engines develop more power than diesel engines because diesel engines are deliberately designed for less power. The reason is torque. Due to a high mean effective pressure, diesel engines provide much more torque than their same sized petrol counterparts. To move a vehicle, torque is the most important factor while your acceleration and top speed depends on power. If we have a look at the calorific value of petrol and diesel both are approximately the same. So, we burn less fuel in a diesel engine because it gives enough torque to pull a vehicle at a low power rating. So, its we who are actually letting the petrol engines develop more power so that torque values match the desired limit. a petrol engine of 75hp develops a torque of around 100Nm while a diesel engine of 75hp may develop a torque of around 180Nm. So if we need 100 Nm to pull a vehicle easily, we can go for a lower power diesel engine and hence lower the fuel consumption.