I finally got to the hangar and measured out my S5 turbo flywheel and the remains of my S5 flexplate. The results are very encouraging, even as good as the possibly could be to make the swap, but I only had ten min at the hangar before I had to leave to pick up my daughter from daycare, so they are one try and slightly sloppy... I make no guarantees. The height measurements of the flex plate were particularly suspect because, well, mine is all warped and broken.
Ring Gear Diameter - Perfect fit. As we suspected, same size, same tooth spacing.
Ring Gear Fore-Aft Placement - As measured from the underside of the big nut. (for all further reference, aft means aft in the CAR). The flex plate puts the aft side of the ring gear 1.290 inches from the front of the big nut. The flywheel puts it 0.913. So the flex plate puts the ring gear (appx) 0.377 in. further aft. This is
actually fortuitous because it just so happens that the ring gear thickness is .365 ... So all we have to do to fix the discrepancy is weld and extra ring gears onto to the flywheel ring gear and there will be teeth that the starter can reach:(bottom of the page.. the cost $80)
http://mazdatrix.com/flywheel.htmIt may also be possible to fix the discrepancy by changing the starter... will look into that.
Damper Plate Placement - On the flywheel, the mounting surface is proud (or aft) of the ring gear. On the flex plate, the mounting surface is recessed (or forward) from the ring gear. And it all pretty much works out. That position on the flywheel will vary somewhat depending on which flywheel you have and how much wear you have on the clutch slip surface. But on my (I assume well-worn) flywheel the placement was 0.965 while the
flex plate was 0.950. Pretty damn close and given measurement error it might me meant to be right on. Or, any difference could be made up by trimming down the spline on the damper plate or removing or adding spacers between the two.
So in my mind, a flywheel is the way to go. Stout, easy to get, pick your weight, only mods seem to be drilling the mounting holes and welding on a second gear ring.
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David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.nethttp://RotaryRoster.net