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.

[ThinAir]

I'm not planning on an engine build anytime soon, but I'm always curious to understand the principles involved for when that time comes.

In may case, I "designed" an engine that would be pretty much a stock 2.0L that runs factory FI. What I changed was the use of flat-top Euro pistons and an Elgin cam that is more "performance" than stock, but made for factory FI. I calculated the deck height to give me 8:1 CR. I run regular unleaded fuel and it seems to do well.

Although I'm pretty satisfied with what I've got, I always wonder about some of the decisions I made and I would likely buy something next time from a builder like Jake or McMark. My questions about CR are to help me better understand how to evaluate options when the next time comes around.