What's Compression Ratio got to do with it? Options

[ThinAir]

When I built my 2.0L I had the understanding that if you wanted to run Regular fuel the highest compression ratio you could have was 8:1. I don't have any idea now where that came from.

In the thread about his air-cooled event, Jake just posted this: "The 356 engine is a 2.4, it made 224HP @ 9:1 CR on pump gas."

Now I know that there is more to one of Jake's engines than just the CR, but it got me to wondering:
1. What is the maximum CR you can run with Regular fuel?
2. What is the relationship of CR to performance? Do you always get more HP by running higher CR if everything else is the same?

Understanding this concept might be helpful the next time someone builds an engine, buys one from Jake, or has one built for them by someone else.

[Madswede]

[EDIT: I just realized that I'm once again doing a bit of a OT thread hijack, given the original question. My bad (IMG:style_emoticons/default/hijacked.gif)] My experience has been (with my 11:1 CR 968) that altitude (and thus lower mass of oxygen per given volume) is a prime factor as well. I've run very successfully on mid-octane and occasionally lower while motoring around from 5200 ft - 10,000 ft.

Since you live at about the same average elevation than I live and work in Ernie, I would bet that (since both of our motors are NA) that your motor would run well enough on lower octane gasoline ... but then again, since you're carb'd I dunno. (IMG:style_emoticons/default/unsure.gif) I know the computer in my 968 probably dials back the fuel mixture given what the MAF and O2 sensors are reading at high altitude, but your carbs...

[ThinAir]

... but then again, since you're carb'd I dunno. (IMG:style_emoticons/default/unsure.gif)

CARB'D??? Never! Factory 2.0L D-Jet FI

[Madswede]

... but then again, since you're carb'd I dunno. (IMG:style_emoticons/default/unsure.gif)

CARB'D??? Never! Factory 2.0L D-Jet FI

Of course, it says so right in your signature ... damn! I'm going batty. My apologies.