ok, so on the shelf I have a TB03, TB0356, and a TB0363. I googled a bit and it says they all have slightly different size compressor wheels with the TB03 being slightly smaller than a 60 wheel, yet they all say .42 a/r comp and .48 a/r exhaust housings. someone shed some light please!

 

Are you possibly not considering wheel design? With AR ratio, inlet/outlet, and wheel diameter all the same, the wheel's design itself can make a tremendous impact on its efficency range. Take a close look at the number of blades, angle of the blades, and if they are straight or curved. Some wheels have very interesting designs that are a key factor to the behavior of the turbo it is installed in. Thats about as far as my understanding goes and this is an area I am definitely not well versed in.

 

I read something similar, but I don't really see any difference in the comp wheels, but I'm tired and will look closer tomorrow.

 

taking the compressor housing off is easy enough. measure the inducer of each and your can determine the what size wheel it is.

fwiw, you wanna use the largest wheel, coupled with the cleanest/newest turbo parts from the rest.