Best way to measure rotor bath??

JustJeff · 01-04-2011, 11:49 AM

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 · 01-04-2011, 08:36 PM

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 · 01-04-2011, 10:00 PM

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

rxspeed7 · 01-04-2011, 10:09 PM

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 · 01-04-2011, 10:54 PM

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 · 01-05-2011, 08:52 AM

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 · 02-19-2011, 11:42 PM

http://www.knology.net/~rv7rotary/Ro...0nitriding.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

01-04-2011, 11:49 AM	#1
JustJeff RCC Contributor Join Date: Mar 2008 Posts: 505 Rep Power: 18	Best way to measure rotor bath?? 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?

01-04-2011, 08:36 PM	#2
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	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. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

01-04-2011, 10:00 PM	#3
vex RCC Loves Me Not You Join Date: Jul 2008 Location: Influx. Posts: 2,113 Rep Power: 20	Could just use putty. Then measure or displace the positive relief. __________________ The Official FC Radiator Thread My Project Thread: Cerberus CCVT Virginia Rotary Group

01-04-2011, 10:54 PM	#5
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	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? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-19-2011, 11:42 PM	#7
My5ABaby Sigh..... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 2,377 Rep Power: 20	http://www.knology.net/~rv7rotary/Ro...0nitriding.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 __________________ 1986 Sport: 132k miles, 5A (Sapphire Blue Metallic), Tokico Blues, Racing Beat Springs, Custom LED tailights (only S4 LED tails in the world), SSR Mark II, Racing Beat exhaust, S5 black interior, Rotary Resurrection rebuild at 120k miles Community Service Manual RotorWiki "Imagination costs nothing; we could build square locomotives or fly to Mars" - Felix Wankel Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the "present."