• NEW RANGE OF TURBOCHARGERS -GBT
    Owen Developments - suppliers to the BTCC, Indy Lights and MINI Challenge and multiple Championship winners - is pleased to announce that the next step in the companies history is here; the Owen Developments GBT Turbocharger range.

Choosing a Turbocharger Guide - Part 1

18 May 2016

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

When selecting a turbocharger there are three main variables to consider; the compressor wheel size, the turbine wheel size and the A/R ratio of the turbine housing. These factors have the greatest effect on a turbocharger’s power and how quickly it spools, but it is important to remember that power and spool directly affect each other and you will have to compromise between them. Working backwards from your power aims we can specify a turbocharger suited to your application with the best possible spool characteristics.

It is strongly recommended to talk to a technical advisor about your application before ordering a turbocharger, different engine configurations and capacities benefit from subtly different approaches to turbocharger specification.

 Compressor Wheel

The compressor wheel is the part which actually makes the boost pressure and therefore the power. Compressor wheel size is the main factor determining the power rating and response of the turbo, the larger the wheel is the more power it can make, but the more energy is needed to spin it which slows spool (compressor wheel design). Compressor wheels are designed to operate in specific RPM ranges (from ~60,000rpm for larger wheels up to ~200,000rpm for small ones), so correctly sizing the turbine wheel and turbine housing directly affect how well the compressor will work.

Choose a compressor wheel based on your power aims, for the best throttle response choose the smallest wheel which can make your power. Take note of which turbine wheel/frame sizes the compressor wheel can be fitted to.

 

COMPRESSOR

 

Power

 

Wheel

Lower

Upper

Frame Size

65

300

400

28

68

300

490

28

71

400

540

28/30

73

450

570

28/30

76

500

600

30

79

500

650

30/35

82

500

700

35

86

600

750

35/37

88

600

820

37

94

500

900

37/40

105

600

1200

40/42

Upper power figures based on a 2.0L engine

 

 Turbine Wheel (Frame Size)

Sizing the turbine wheel (also referred to as frame size) is a compromise of three competing attributes; to give enough drive to the compressor wheel for it to work efficiently, without choking the flow of exhaust gases out of the engine, while keeping a drivable power curve. Changing the turbine housing A/R is a useful way of ‘fine-tuning’ your choice of turbine wheel to a point, but having too large or small a turbine wheel will ruin the performance of the turbo.

Which compressor wheel can make your power aims determines which turbine wheels/frame sizes are available to you. Some compressor wheels are only available with a certain turbine wheel, but when options are available a rule of thumb to use is pick the larger one when power is a priority, pick the smaller one when response is a priority. If you’re unsure, contact us.

 

TURBINE

 

Power

Wheel

Lower

Upper

Avg.

28

300

540

420

30

400

600

500

35

500

750

625

37

600

900

750

40

500

900

700

42

600

1200

900

Upper power figures based on a 2.0L engine

 

 Turbine Housing

Turbine housing A/R is used to change the flow capacity of the housing heavily influencing the response and maximum power of the turbocharger. Using a smaller A/R housing increases the exhaust gas velocity at the turbine wheel which gives a rapid boost rise and a more responsive engine. However by doing so you limit the top end power of the turbo as the gas flow is limited by the physical size of the housing, which chokes it. Using a larger A/R housing lowers the gas velocity which slows the turbo spooling but does reduce backpressure unlocking more top end power. What application the turbo will be used in is a major factor in deciding a turbine A/R; rally turbos which prioritise response will have a relatively small A/R whereas a drag racing turbo will have a much larger A/R to unlock all the turbo’s potential power with no regard to response.

Use the smallest turbine A/R which can make your power aims on your frame size. There are some exceptions, for example instead of putting a GT28 or a GT30 in a .8 A/R housing better results can be achieved by going up a turbine wheel/frame size and using a .6 A/R housing. If you’re unsure, contact us.

TURBINE A/R

Wheel

A/R

Upper

28

~.6

450

28

~.8

500

28

~1.0

*

30

~.6

550

30

~.8

600

30

~1.0

600*

35

~.6

700

35

~.8

750

35

~1.0

*

Upper power figures based on a 2.0L engine

* ~1.0A/R housings are almost never used as better performance can be obtained by using a larger turbine wheel in a smaller A/R housing

Even with these factors taken into consideration there are still special cases which do not conform to these guidelines, such as diesels, rotaries and high revving engines like the Honda VTEC. Owen Developments strongly recommend you contact us for advice on your turbocharger’s specification before ordering.

Owen Developments is one of Europe’s premier high performance forced induction specialist, with a proven track record of supplying turbochargers to a global customer base covering the motorsport, performance aftermarket and OEM sectors. Owen Developments is the sole turbo supplier to the British Touring Car Championship, the highly competitive one-make MINI Challenge and Indy Lights (Indycar’s feeder series).

 

 
Newsletter Signup

Find us on Facebook
Copyright © 2017 Owen Developments  |  All Rights Reserved
Owen Developments Ltd
28 Kingston Business Park
Kingston Bagpuize
Oxford
Oxfordshire
OX13 5AS

t: 01865 821062
w: www.owendevelopments.co.uk
e: enquiries@owendevelopments.co.uk
Seeking Advice?
Please fill in the form below.
*Your name is required.
*Your email address is required.*Please enter a valid email address.
 Exceeded maximum number of characters.
COOKIE NOTICE

This site uses cookies to store information on your computer/device. By using this site you agree that we may store and access cookies on your device.

The cookies we use are required to make our site work and to gather information on the number of visitors to this website.

This information is ENTIRELY ANONYMOUS; no personal information is captured or stored. To find out more, see our privacy policy.

please click this button to acknowledge that you accept cookies from this site and to dismiss this message