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

[Mark Henry]

Kind of funny way of asking what is the max HP a Type 4 engine can make. (IMG:style_emoticons/default/biggrin.gif)

Often when these questions are asked, you have a younger guy, a novice who is only looking at the top number.

You can run at lower CR
The factory CR is about normal for the era.
Over about 9.5 you need to twin plug.
At to 12:1 your done for gas

Above has too many variables, but is ballpark for an aircooled, you can get a bit higher out of a watercooled