What is the difference between turbochargers on diesel and petrol engines? Basically the common

principles of their operation are the same as well as the way in which they intake air and exhaust gases,

regardless if you are adding a turbo to a petrol or a diesel engine. Furthermore, the basic design and

components that go into petrol and diesel turbochargers are also pretty much identical. What makes them

different are the combustion pressures and temperatures, operating RPM range, and the driving cycle. It is

apparent that diesel and petrol engines differ in one way or another hence their turbochargers will need

some tweaking for them to work perfectly.

First of all, we need to understand the idea behind a

turbocharger. A turbocharger is used so as to increase the

amount of air and fuel that enters each combustion

chamber in the engine, in order to provide additional

power from each explosion.

Diesel, which is not as combustible as petrol, needs higher

pressure to ignite the air/fuel mix in the combustion

chamber of diesel engines. With these higher pressures, diesel engines thus need to be stronger in terms of

using bigger, heavier components, which in turn makes it harder for them to operate well at higher RPMs.

What happens next is that diesel engines will need to operate at much lower and narrower RPM band as

compared to petrol engines, hence making it much more to difficult draw in enough air into the

combustion chambers. The fact that diesel is also burning at a lower temperature causes it to create more

exhaust gases. Turbocharging comes into play by increasing airflow to the engine instead of increasing

combustion pressures. With a larger turbine section that is capable of handling both the high volume of

exhaust gases, diesel turbochargers are generally bigger and are installed for engines’ dependability and

reliability.

On the other hand, being far more volatile and

combustible, petrol burns hotter, ignites quicker and

does not need to be atomised for combustion,

therefore pressures inside the combustion chambers

need not be that high. Using a lower air-to-fuel ratio

than diesel fuel, petrol engines are smaller

displacement engines that need to operate at a higher

and wider RPM range for drivability and thus petrol

burns at a higher temperature. The addition of a turbo to petrol engines is so that the engine power will

increase. Designed to run at much higher RPMs, petrol turbochargers have to spin at an incredibly high rate

of speed, which subsequently provide a higher boost in pressure, without significantly increasing airflow.

Additionally, petrol turbochargers need to get up to speed more quickly due to operating at a much wider

band of RPMs. As the increased RPM of both the engine and the turbocharger creates a lot of heat, many

turbochargers utilise the back pressure of these hot gasses in order to improve efficiency and operation.