Type 4 mechanical compression ratio, Why is the factory compression so low? Options

[Beebo Kanelle]

OK, here's a fun one for the novice to ponder and you experts to answer:

Why is the factory mechanical CR so low?

and for reference, what is the highest mechanical CR that can be physically achieved? assume no octane limitations -

I'm just looking for the design limit for the highest CR that can be / has been in a Type 4 engine using available technology.

Thanks

[r_towle]

Look at how the 911 turbo seals the head to cylinder.
Basically a small diameter wire machined into the head and cylinder, then crushed when torqued down.

[Mark Henry]

Look at how the 911 turbo seals the head to cylinder.
Basically a small diameter wire machined into the head and cylinder, then crushed when torqued down.

No Rich, you don't understand what I mean by fire ring .
The Fire ring that is match machined into a high performance 911 turbo head and cylinder. The ring also stops cylinder head movement or shuffle.

(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-26-1455386123.1.jpg)

BTW I often work on a 500+hp porsche 911 turbo 3.8L high performance engine that has over 100hp/cyl.
The owner has well over $80K into the engine alone...this time around.