NA versus NB crank dampers
 

As this is a turbo forum, I understand that this information may be less relevant to others as it is to me. However, I do recognize the lack of support elsewhereo n reliable forums for supercharged cars and I would like to share my findings as I haven't really come across a solid source elsewhere that connects these dots to this issue.

When trying to fit a newer machined TDR overlay pulley (customized at a local shop for 7-ribs instead of 4, irrelevent to this fitment though) I noticed the pulley did not slip into the damper as my older one did. The TDR overlay did, however, fit right into an NB damper which struck an interest of mine. Had I been any other less resourceful customer I'd have raged to track dog racing for a refund! For any relevanceo n the matter, please refer to the photos for the various differences and pssible pros/cons to your particular applications:

Left side: new TDR overlay
Right side: Older TDR overlay
https://www.miataturbo.net/attachmen...ine=1370381927

Left side: new TDR overlay with 2003 damper
Right side: Older TDR overlay with 1996 damper
https://www.miataturbo.net/attachmen...ine=1370381927

Notice the difference in the chamfer from old to new:
https://www.miataturbo.net/attachmen...ine=1370381927
https://www.miataturbo.net/attachmen...ine=1370381927

Left side: 1996 damper
Right side: 2003 damper
https://www.miataturbo.net/attachmen...ine=1370381927
https://www.miataturbo.net/attachmen...ine=1370381927

2003 damper inner hub area almost looks like a billet piece, nice 90 degree angle:
https://www.miataturbo.net/attachmen...ine=1370381927

1996 damper inner hub with a clearly intrusive 1/4 circular ridge around the circumference (the purpose for the chamfer design on the overlay):
https://www.miataturbo.net/attachmen...ine=1370381927

1996 inner hub diameter (for reference to whatever overlay you may intend to use, be sure it clears!):
https://www.miataturbo.net/attachmen...ine=1370381927

2003 inner hub diameter:
https://www.miataturbo.net/attachmen...ine=1370381927

also note the design differences of the face of the dampers that the NA one has sort of a protruding inner section whereas the NB damper is almost cut flat on the face.

Hope this helps someone stuck in a weird dead end on an unexpected issue!