A/R of a turbo?

[kwazza11]

just wondering what the A/R is and how they calculate it?

anyone?

Karlos

[Roy]

The turbo has a compressor, and a turbine (sometimes called exhaust wheel etc etc).

Both the turbo and compressor have an linlet and outlet.

The A/R is simply the ratio of the surface areas from inlet to outlet. The smaller the number say 0.50 the bigger the increase in gas velocity which helps turbo response, but can choke up flow.

[Steve]

Think you may be slightly off target there Roy, or I am having trouble understanding what you wrote.

A/R ratio stands for Area to Radius ratio. It applies to both the compressor and turbine housing.

Area = the area of the exhaust port of the housing,

Radius = the radius of the housing

I am about 95% certain that this is correct.

[Roy]

Yeh wasnt very clear was i.

Yeh both the compressor and turbines have A/R, and yes stands for Area / Raduis.

...simply the ratio of the surface areas from inlet to outlet.

Its not a clear way of describing what i meant. How about A- the surface area at a given point, either inlet, outlet or somewhere bewtween,

and R- is the radius from the centre of the turbine shaft to the centroid of the cross-sectional area A.

A/R = constant, so A1/R1 = A2/R2 = A3/R3 etc etc, with the smaller Area giving increased gas velocity and the greater the R the greater turbine shaft torque to drive the compressor

But as i understand it is generall the Area that sees the most change when sizing exhaust housings etc

[kwazza11]

hmm... ok i've got a basic understanding, still alittle confusing though but atleast i know now why a/r ratios affect your turbo selection

thanks guys

Karlos