2,4 T4 201,1Hp wants more!

[Piledriver]

Based on my limited historical background, gas filled would NOT be the best, either c-rings or the ported hollow ones would be...
...with the inner dia of the ring exposed to combustion chamber pressures.

(This of course based on only experience with high pressure pumps and vacuum equipment, and a bit of googling)

C-rings shouldn't cost more than a few dollars...
(OK, maybe $$ in exotic alloy)

The gas fill pressure of 650 PSI isn't a lot, is it more than peak combustion pressure?

If not, either of the other choices would be orders of magnitude cheaper and have superior performance to the gas filled jobs.

A C-ring likely would have several times the compliance, for 1/10th of the price... Maybe less.

I almost BET that's what the Porsche ones are.

It's how piston rings work, `cept without all the sliding bit...

Mr. Sumen, where art thou?