Turbo Engineering

What is Engine Matching?

The turbo is an integral part of the engine and its performance characteristics must be closely matched to enable the engine to achieve the desired torque, power and fuel consumption rating.

During the system development, many engineering factors, such as temperature, pressure and airflow, must be considered to optimise compressor efficiency. An incorrectly designed turbo with poor compressor efficiency would cause an entire engine system to suffer.

This subsequently causes premature turbo failure, creates safety hazard, leads to consequential engine damage, increases downtime and cost.

We highlight 2 of the many engineering factors:

Compressor Characteristics

Efficiency Contours
The efficiency contours depict the regional efficiency of the compressor set. This efficiency is simply the percentage of turbo shaft power that converts to actual air compression. When sizing a turbo, it is important to maintain the proposed lugline with a high efficiency range on the map. The ideal position is the blue area.

Surge Line
The surge region, located on the left-hand side of the compressor map, is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long period of time, bearing failures may occur.

Choke Line
The choke line is on the right hand-side of the compressor map and represents the flow limit. When a turbocharger is run deep into choke, turbo speeds will increase dramatically while compressor efficiency will plunge (very high compressor outlet temps), and turbo durability will be compromised.

Sizing of Turbine Housing

 This sizing is determined by the Area/Radius (A/R) Ratio. A correctly matched turbine housing ensures the matching turbo speed and engine backpressure. An incorrect A/R may lead to

• turbo overspeeding, causing poorcompressor efficiency and
• high backpressure, causing poor engine volumetric efficiency