15 Turbocharger Facts You Did Not Know
• Fully synthetic oils and mineral oils do not mix. In severe cases they can coagulate.
• If the engine's oil pressure is low, the turbocharger will be the first engine component to fail.
• Piston blow-by and the resulting crankcase/sump pressure if not vented off adequately is the most common cause of turbocharger oil leakage.
• The most common contaminants found in the oil are 'free floating' carbon deposits, fuel and the by-products of combustion.
• A typical diesel turbocharger with rotor speeds in excess of 200,000 R. P.M. will have a blade speed on the compressor wheel of 850 miles per hour.
• Many operators assume, quite wrongly, that if they run an engine with dirty or contaminated oil, the oil filter will remove any foreign matter before it reaches the engine and more importantly the turbocharger.
• Oil delay of a mere four seconds will start to cause journal and thrust bearing wear. Delay of just eight seconds can cause irreparable damage. This damage will not necessarily manifest itself immediately, the final failure may occur after several days.
• The average temperature of the exhaust gas, at the entry point to a diesel turbo, is 800 degrees centigrade. A petrol engine can reach 1000 degrees, glowing bright yellow. Hot enough to melt window glass.
• New generation turbocharger impellers rotate at up to 220,000 revs per minute. The impellers on a Boeing 747 engine rotate at about 7,000 revs in comparison.
• The air entering the compressor impeller of the turbocharger can be traveling at a speed close to mach 1.
• At average engine revs, a medium size turbocharger will swallow 130 cubic feet of air per minute, equivalent to the interior volume of a transit van.
• Turbo shaft balance is crucial – imbalance at maximum revs equivalent to a 2 kilogram force is acceptable. We often find turbos supplied for service with 6 kilos of imbalance. This is equivalent to driving along with a house brick attached to your wheel rim.
• The "hot end" turbine blades in a turbocharger, are made from a high nickel content alloy, as used in jet aircraft engines. A blade will travel in the region of 820 mph at average engine speed, and the exhaust gas entering it will be supersonic.
• The turbocharger rotor will accelerate from 20,000 revs per minute to over 150,000 revs per minute in less than one second.
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