Whats the A/R on the turbo mean?

[Focusonme13]

i have 2 turbos...one says A/R 81...one says A/R 60....im tryin to see how big the turbos r...can some1 help me out

 

[psychlow]

A/R = Area to Radius Ratio. I'm looking for a picture of it because it's easier to explain with a photo than it is in words.

EDIT: Here we go.

The turbine housing A/R (area/radius) ratio is the area (A) of any turbine inlet scroll cross-section divided by the distance from the center of that cross-section to the center of the turbine shaft (R). For any given turbine housing, A and R vary in the same proportions, so all As divided by their corresponding Rs yield the same dividend--which is the A/R ratio.

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[Bullitt]

just one little note to add, this then means that a larger A/R increases lag, but overall flow and therefore boost, as less of the air is then forced out the wastegate.

 

[Focusonme13]

thanx...its just some one told me the the A/R was the "trim" of the turbo....like A/R 81.....was an .81 trim....bu ti didnt think so

 

[Bullitt]

Trim if i remember correctly, is ((exducer)/(inducer))^2 * 100. I may have those inverted, but thats your trim. Its a ratio of your impeller wheels. Trim will be a bit more helpful in telling you what your spool and overall boost will be, although it wont actually tell you this, just give you a general idea, something i dont think you can get from just an A/R (someone correct me if i'm wrong here).

 

[sweet97]

TRIM= 100*(inducer/exducer)^2