Does a Turbo Spin at Idle [How fast does a turbo really spin]

In this article we will be covering a common misconception that seems to be circulating throughout the automotive world, does a turbo spin at idle?

A turbo spins all the time once your engine is running. This is due to exhaust gasses passing through the turbocharger and causing the turbine wheel to continuously spin. Although the wheel is spinning, it will not spin fast enough to create a sufficient amount of boost pressure needed to power the engine.

honda civic full boost turbo

A turbocharger works by converting the energy from the exhaust gasses into mechanical energy. This is done by installing the turbocharger inline with the exhaust immediately below the exhaust header.

When the engine runs it creates exhaust gasses, these gasses then exit your engine via the exhaust and through the turbo housing. Inside the turbo, housing is a turbine wheel which is connected to a compressor wheel via a common shaft.

What causes a turbo to spin all the time is the pressure of the exhaust gasses leaving the engine, when your engine is running it will continuously pump exhaust gasses through your turbo housing. These gasses then spin the turbine wheel, and this, in turn, will cause the compressor wheel to spin also.

Once your engine has reached a certain RPM the compressor wheel will have built enough pressure inside the turbo housing to create positive pressure inside your inlet manifold. This is the point where you will notice boost starting to kick in due to the large volume of air which has filled the inlet manifold and entered the combustion chambers.

To find out exactly what RPM your turbo kicks in at you should check out this article which covers the topic in a little more depth.

It is important to note that just because your turbo does spin all the time once your engine is running, it does not spin fast enough to create boost at idle, this is due to the very small volume of exhaust gas passing through the turbocharger at idle RPM.

For the full version of how a turbo works I would suggest taking a read of this article which covers how a turbo works step by step, I think its simplicity will surprise you.

How Fast Does a Turbo Spin

A turbo derives its ability to create power from the incredibly fast speed at which the turbine and compressor wheels are capable of spinning.

The speed at which a turbo spins is dependent on the RPM of the engine. At idle a turbocharger has a rotational speed of about 150,000 RPM. Once you increase the RPMs of the engine through acceleration or load, this speed will increase up to about 280,000 RPM when producing full boost.

Because of the speed at which the turbo wheels spin, it is extra important to follow strict servicing intervals and never be tempted to use a cheaper oil for your engine than what is recommended by the manufacturer.

The most common cause of turbo failure is due to dirty contaminated oil which creates resistance between the turbo housing and the shaft bearings.

Ball-bearing turbos in particular are highly prone to failure purely because the engine oil has become contaminated, dirty, and loses its viscosity.

The problem which arises then is that inside the turbo housing becomes caked in old cooked oil leaving a rough unsmooth surface for the bearing to spin on. Once excessive amounts of this coked oil build up on the surface the bearings can no longer spin freely.

Once this begins to happen it becomes much harder for the turbine wheels to rotate which results in an extreme build-up of heat in the turbo.

If this happens, and you continue to use the turbo without taking the appropriate steps to disassemble the turbo and clean it out, the turbo will fail in a short time and may not be repairable depending on the damage it causes to the internal parts.

For a turbocharger to function correctly, its internal parts must be free to spin and move as needs be with little resistance or friction.

The easiest and most effective way to ensure you are taking the best possible care of your turbo is to keep your engine serviced regularly, use good quality engine oil, and most importantly, always follow the correct start-up and shut-down procedures for a turbocharged engine.


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