Advice on ring gapping for 99 Boxster 2.5l

[four0four]

This is speaking from intuition, but it seems that the expander ring generates a radial force for the upper/lower oil rings (note how it mates with them at the rear and presses outward radially) - the expander itself probably doesn't contact the cylinder walls. You can verify this with a few measurements of the depth of the scraper ring and then inner lip of the expander ring.

But yes, that tension is generated by compressing the tabs as you describe. It serves the same purpose as the more standard design I linked in above (the Mahle docs), which is at least for me easier to follow.

[jbranch]

Well, this is something new for me. Thank you for the help and insight. I'm getting wiser every day. Now, if I can just remember where I left my phone.

[four0four]

And good luck with the rest of the rebuild!

I'm happy it helped - I think without that tension you would see (minimally!) absolutely terrible oil consumption.

I cannot help with the phone, I'm afraid