What Is Turbo Charging?

What Is Turbo Charging?

Here is some basic information on turbocharging. Hopefully it will help you understand why turbocharging is a great way to make smooth reliable horsepower. 

Why do people turbocharge their motorcycles, cars, trucks, and airplanes? Why do people drive well over 100 mph when the sign says 65? It is simply for the thrill and rush, the love of speed and power; power that is always there at the twist of the wrist. Turbocharging your motorcycle can easily achieve 50% increase in horsepower, if not more. If you plan on increasing the horsepower over 50%, typically the engine will need internal requirements and additional fuel delivery requirements. If you plan on turbocharging your motorcycle, you must purchase a kit that is well thought out and thoroughly tested. 

How does a turbocharger work? Here is a general rundown. The engine produces exhaust gases that exit via the exhaust ports of the cylinder head. These gases flow through the exhaust manifold into a turbocharger unit as the exhaust gases enter the turbine housing. The velocity of the exhaust gases spools (spins) a propeller blade type of wheel, called the turbine wheel. As this turbine wheel begins to spin, it turns and drives a common shaft. This shaft has another propeller type wheel, called the compressor wheel, on the other end. The compressor stage of the turbo begins to suck air in as the compressor wheel begins to spool. The compressor wheel spools faster and faster and the air becomes compressed, charged air. The faster the wheels spin, the faster the shaft speed, thus, the greater pressure. 

From the compressor stage of the turbine, the charged air exits at a greater velocity and makes its way to the intake side of the engine, through an intercooler, or simply the intake plumbing. An intercooler is a huge heat exchanger, which is like a radiator, but for air. It cools the intake air temperature as it enters the engine. Because intercoolers have to be so large in size to work to their full potential, it is often hard, if not impossible, to plumb an intercooler to the side of a motorcycle, without hurting the overall appearance of the motorcycle. As more air is forced into the motor, an additional amount of fuel must also be added. The amount of fuel must be proportionate with the amount of air that is supplied to the motor. More air, plus more fuel, equals more power. 

Turbo boost, a turbocharged engine revolves around one central idea and that is boost. Boost is defined as the increase in manifold pressure above atmospheric pressure. Boost is a gauge measurement of a turbocharger compressor’s discharged pressure. This basically means the value (amount) of charge pressurized air coming out of the turbocharger. The higher the boost, the more air will be forced to the motor; therefore, more horsepower will be made. Boost is measured in PSI, pounds per square inch, or bar, inches in mercury level. 


Turbocharger – The turbocharger is an exhaust driven compressor. It consists of 3 main housings.

The turbine housing, which drives the compressor stage, is the side connected to the exhaust.

The center section which houses the common shaft. The center section houses the shaft bushings or bearings. Oil is fed into this housing to lubricate and help cool the center section.

The compressor housing from which the charged air is created and discharged to intake side of engine.

The turbo has two propeller type wheels connected by the common shaft. The “turbine wheel” and the “compressor wheel,” both spool up to create the “charged air.” 

Exhaust manifold – The exhaust manifold holds the turbocharger and mounts it to the motor. The exhaust manifold directs the exhaust gases from the exhaust ports to the turbocharger inlet. It is usually made of cast iron, mild steel, or stainless steel. 

Down pipe or Tail pipe – The down pipe is connected to the side of the turbine housing that directs and lets exhaust gases out of the turbo, through the exhaust system. 

Intercooler – The intercooler is a giant heat exchanger that cools down the temperature of the charged air. Usually when charged air is created, it is hot. So it is good to cool it down to help make the most power possible without detonation. Not all turbo systems use and intercooler. Our stage 1 U-Rod turbo system doesn’t use an intercooler. Low boost levels (8-9 lbs.) and simple clean install doesn’t require the use of an intercooler. The stage 2 high output system will require an intercooler to help suppress detonation. 

Blow off valve – A blow off valve is a spring loaded valve usually placed on the pipe between the compressor housing and the throttle body, used to help prevent compressor surge. Basically, this helps the turbo last longer and increase responsiveness. Blow off valves give a distinctive, yet impressive hissing sound. It’s the sound that screams. ‘Lookout, I’m turbocharged.’ 

High pressure fuel pump – along with a boost sensitive fuel regulator is usually needed to supply enough fuel. A boost sensing regulator will feed the injections with more fuel when on boost, at a linear rate. 

Waste gate – The waste gate primarily controls boost pressure. It is an exhaust bypass valve that opens and closes to let out or keep exhaust gases. It maintains the turbocharger’s shaft speed by this open and close action. When it opens, exhaust gases leave via the down pipe and exhaust. Thus, the shaft speed is slowed down. When it stays shut, the exhaust gases increase shaft speed by spooling the turbine wheel.