i thought this forum was where this question belonged so pelase help me out

 

A/R stands for area ratio and is a mathematical description of the cross sectional area of the turbine hosing inlet divided by the radius described by the center of the turbine wheel to the center of the the tubine hosing inlet.

A large A/R housing has good flow, less backpressure and creates more top-end power at the same boost pressure by improving the volumetric efficiency. It will also spool more slowly. Conversely, a small A/R housing has less flow and more backpressure but has quicker turbo spool-up characteristics.

Hope this helps

 

Area to Radius Ratio

A/R Ratio = Area / Radius

Think of the turbo scroll as a rolled-up nozzle. It's just like putting your finger partially over the end of a garden hose. A smaller AR (more taper) causes more restriction and yields more velocity which initially spools the turbo faster, but the cost is a reduction in area, and therefore pressure and torque, which is required for higher flow rates.

The AR ratio is usually constant at any point around the scroll, although this picture only shows one point.

 

so when will we see variable a/r housings? or is this what variable geometry turbos are? (that already exist) i was under the impression that variable geometry turbos had variable turbines.. not housings.

 

The only variable automotive turbo that I know of is the Aerocharger, which has variable turbine guide vanes, which would approximate a variable AR turbine housing. Aircraft turbine engines usually have variable stator vanes (kinda like a variable AR for the compressor), as well as variable exhaust nozzles for increased performance, and variable intakes for supersonic flight.
http://www.aerocharger.com/aerotech.htm

 

Thanks sooooo much

I knew I could rely on you guys

 

A/R= Aspect Ratio or Area / Radius. Compressor A/R is determined by dividing the radius of the compressor housing by the smallest diameter of the compressor outlet . Exhaust housing A/R is determined by dividing the radius of the exhaust by the smallest diameter of the exhaust inlet . As the A/R numerically increases so does the housings ability to induce/exduce a specific volume of air. Lag and effective power range will also be affected by A/R changes. Look at the pic in Evil Aviators post an this will make sense. Basically I just repeated what everybody else said but this is the info that I have on my site.

 

thank God somebody finally ask this question

 

GOOD STUFF!!!!!!!!!!!!