when you talk turbos for 7.0+ motors, they really arent applicable to the 4 cylinder motors like hondas have. alot of these turbos have a very large turbine side. A/R is a measurement .... the area of the inlet over the radius from the center of the inlet to the center of the turbine wheel. sooo, (the area of the inlet size) divided by (the distance from the center of that inlet to the center of the wheel) = a/r. turbos have 2 a/r ratios ... one for the compressor side and one for the exhaust side. small turbos can have a bigger a/r than big turbos. it all just depends on what the turbo is built for. usually a larger a/r is designed for more exhaust to create spool.