Best way to measure rotor bath??

[JustJeff]

What's the best way to do this? I'm doing a S5 turbo rebuild. I'm crossing my "t" and dotting my "i". I bought a replacement rotor and want to make sure it's in fact a S5 turbo or FD rotor.

If the S5 and FD rotors all weigh the same then measuring the compression bath is the only way to make sure I'm not putting an N/A rotor in my turbo. Correct?

[NoDOHC]

The way that I usually do it is to take a thin piece of lexan or clear acrylic about 4 inches wide and 10 inches long and to drill three holes in it. One in the dead center, and one on each end in the center (2 inches from either edge). Put a film of thick oil on the surface of the rotor (not in the combustion chamber) and pull the plastic down to match the contour of the rotor using a strap around the opposite apex of the rotor (a block of wood across the apex seal groove is handy to avoid cutting the strap). Once the plastic matches the contour, you can fill the dish using the conventional method (syringe or eye dropper).

I have had to make thin metal pieces for the outside to attach the strap to, but usually the lexan bends to the contour of the rotor very nicely.

[vex]

Could just use putty. Then measure or displace the positive relief.

[rxspeed7]

i usually just take a straight edge and place it across the bowl and measure the depth. deeper for turbo and shallower for n/a

[FC Zach]

I'm curious about this as well. What if you dont have the opposite to compare the difference to? What is the cc's it would take to fill either, or the depth of either type of rotor?

[classicauto]

As far as turbo rotors go, S4's are cast/rough bowls. S5 rotors as smooth machined. S6 rotors are machined with tooling lines running along the rotor surface (apex to apex)

[My5ABaby]

http://www.knology.net/~rv7rotary/Rotor%20housing%20machining%20&%20nitriding.htm

Rotor Facts:

If you lay a straight edge across the depression longwise and measure from the bottom of the straight edge to the deepest part of the depression you can determine the compression ratio of the rotor:

- 4mm = 9.7:1 compression ratio

- 5.5mm = 9.4:1

- 7mm = 9.1