[HOLSET®]

Description and Operation of Turbocharger
General Information
A turbocharger is a mechanical device which uses the engine’s exhaust gases to force more air into the engine cylinders. Hot exhaust gas energy is used to turn a turbine wheel and shaft. At the other end of the shaft is the compressor impeller (or compressor wheel), which draws in air and forces it into the engine cylinders.
Supplying increased air mass flow to the engine provides improved engine performance, lower exhaust smoke density, improved operating economy and altitude compensation. The turbocharger has proven to be one of the most beneficial devices for improving engine performance. It performs its job very well, as long as it is properly cared for.

Introduction to Turbocharger Matching
The need for optimised matching over the engine speed range
A standard turbocharger can be perfectly matched to only one particular engine condition, eg maximum torque speed or maximum load speed. At this engine speed, the turbocharger supplies the optimum mass of air to give the required air/fuel ratio. At other speeds the air/fuel ratio cannot be held at the optimum hence fuel consumption and emission levels worsen.
Engine emission legislations have forced manufacturers to improve their engine efficiencies, particularly at low speeds where low air/fuel ratios cause high smoke levels.
The Holset turbocharger is carefully matched to meet the required engine characteristics during application engineering. It is important that this match is maintained by using only Holset original turbine and compressor parts.

The importance of correctly servicing the turbocharger
A turbocharger requires accurate assembly at point of manufacture. It is very important to adhere to setting limits when servicing the turbocharger, as failure to do so could result in turbocharger or engine failure.

Effects of wrong match
Possible consequences if turbocharger boost pressure is too low:-
• Engine runs fuel rich
• Exhaust temperature increase
• Hydrocarbon levels increase
• High cylinder temperature risks damage to engine pistons
• Fuel consumption increase
• Smoke levels increase
• Risks of failing emissions tests

Possible consequences if turbocharger boost pressure is too high:-
• Engine runs fuel weak (lean)
• Excessive boost overspeeds turbocharger
• Increased cylinder pressure risks damage to engine head gasket, pistons and valves
• Nitrous oxide levels increase
• Turbocharger bearing failure and wheel fatigue problems
• Intercooler load increases causing engine to overheat, risking piston damage