Turbocharger FAQ's
A turbocharger is a device that makes power by forcing air into the engine. By compressing air, the turbocharger squeezes air into the engine, which also brings in more fuel. This is called the 'boost pressure' and is typically around 14 psi. More fuel and more air mean's bigger explosions in each cylinder. And more explosions mean's more power to the engine.
How do Turbochargers work?
A turbocharger is an exhaust-driven air compressor. It becomes an air compressor by utilising expanded exhaust gases from the engine. The exhaust gas pressure and the heat energy extracted from the gas causes the turbine wheel to rotate, thus driving the compressor wheel through a common shaft. Exhaust temperature and pressure drop as they pass through the turbine housing and into the atmosphere.
The rotating compressor wheel draws air in and the blades accelerate and expel the air into the compressor housing. Once into the compressor housing, the air is compressed and flows toward the intake manifold, pressurizing the intake in a measurable form we call boost pressure.
A turbo spins very fast on full boost. Most peak between 80,000 to 150,000 rpm depending on size. That’s 2500 revolutions per second!
Why do Turbochargers fail?
Lack of oil:
Faulty lubrication systems and contaminated oil can cause the engine to overheat and bring on premature bearing failure.
Reduced air supply:
A kink, plugged or undersized inlets can cause high temps that can lead to a cracked turbine housing. Poor air supply can create a vacuum in the compressor, which induces oil leakage. That can cause engine smoke and damage oil seals.
Improper fueling:
Creates heat causing turbine housing scaling and cracking. Shutting down an engine too quickly. An engine that is shut down too fast can causing the oil to coke up inside the oil drain and forcing the oil out the turbine and compressor seals. Foreign objects. The rapidly spinning parts in a turbocharger can disintegrate rapidly when foreign objects strike them.
Inter-Coolers
An inter-cooler works and looks the same as a normal radiator of a car. The only difference is that an inter-cooler cools air instead of water. Both the inter-cooler and the radiator need to have air passing through/over them to make them work.
At wide open throttle and full boost the hot compressed air coming from a turbocharger is probably between 125 and 180 degree C depending on the particular turbo, boost pressure, outside air temperature, etc.. We want to cool it down, which reduces its volume so we can pack more air molecules into the cylinders and reduce the engine's likelihood of detonation.
Turbo chargers heat the air in the process of compressing it. The gas law, refers to the absolute zero temperature of -273 degree C. (Kelvin). This means that for every 60 degree C, the density changes by 10%. Assuming the engines volumetric efficiency stays the same, then we get 10% more power out of an engine, if we can reduce the inlet air temperature by 60 degree C. Inter-coolers are very important for turbo charged engines, because of the extra heating caused by the exhaust.
