Turbocharger Failures, Preventative care and tips
We have seen an increasing amount of turbocharger failures, some of these resulting in engines “blowing up” and having to be replaced due to shattered blades from the turbines entering the engine.
If you drive a turbocharged vehicle they need to be treated slightly differently from a “normally aspirated” engine. A turbocharger may be fitted to petrol or a diesel engine and will enable the engine to produce similar power output to a larger engine. How? Well it uses the exhaust gas pressure exiting the engine to push extra air into the inlet side of the engine. The faster the exhaust gas exits the more air, and therefore oxygen, is “rammed” into the inlet side and helps the petrol/diesel burn far more efficiently producing more power, up to a 30% increase allowing smaller more compact engines.
Wow! Something for nothing? Well not completely. turbochargers are expensive and have a very hard life, they are exposed to extremely high temperatures of around 800 degrees C for diesels and around 1000 degrees C for petrol’s very high revolutions of up to and sometimes exceeding 200,000 rpm ( Jumbo jet engines rev at about 7000 rpm), the air entering the turbo at average engine speed will be supersonic and the turbine tips will be traveling at about 820 mph, the turbocharger will have to accelerate from 20,000 rpm to 150,000 rpm in one second.
The life blood of a turbocharger, as detailed below, is oil. The oil has to be a very high grade fully synthetic. If the turbocharger is starved of oil for four seconds it will damage the bearings and journals, eight second and it will cause irreparable damage.
If the engine oil pressure drops the first casualty will be the turbocharger.
- Use the correct oil, do not mix oils they can coagulate. Do not let the oil level fall below the minimum mark on the dipstick.
- Change the oil and filter at regular intervals or when the service interval dictates and do not “extend” the service intervals.
- Air filters must be changed regularly or when the service intervals dictate.
- If the turbocharger has been working very hard i.e. motorway use or hard driving the engine should be left to idle for a few minutes to allow the turbocharger to cool down. Think next time you pull off the motorway into the services!
- The air filter (not shown) through which ambient air passes before entering the compressor
- The air is then compressed which raises the air’s density (mass / unit volume)
- Many turbocharged engines have a charge air cooler (aka inter-cooler) that cools the compressed air to further increase its density and to increase resistance to detonation
- After passing through the intake manifold, the air enters the engine’s cylinders, which contain a fixed volume. Since the air is at elevated density, each cylinder can draw in an increased mass flow rate of air. Higher air mass flow rate allows a higher fuel flow rate (with similar air/fuel ratio). Combusting more fuel results in more power being produced for a given size or displacement.
- After the fuel is burned in the cylinder it is exhausted during the cylinder’s exhaust stroke in to the exhaust manifold
- The high temperature gas then continues on to the turbine. The turbine creates back pressure on the engine which means engine exhaust pressure is higher than atmospheric pressure
- A pressure and temperature drop occurs (expansion) across the turbine, which harnesses the exhaust gas’ energy to provide the power necessary to drive the compressor.
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