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

[McMark]

If you're looking to improve thermodynamic efficiency, why are we talking about compression? Why are we talking about horsepower? Neither of things have any direct connection to head cooling.

You're being very cagey about what you're actually trying to do. It makes it hard to help.

[Mark Henry]

If you're looking to improve thermodynamic efficiency, why are we talking about compression? Why are we talking about horsepower? Neither of things have any direct connection to head cooling.

You're being very cagey about what you're actually trying to do. It makes it hard to help.

(IMG:style_emoticons/default/agree.gif)
And what is your budget?

We've seen our share of new members posting they want a 200hp type four, then after countless posts we find out their entire budget is $2k and a case of beer. (IMG:style_emoticons/default/blink.gif)
(IMG:style_emoticons/default/beer3.gif)

[jd74914]

If you're looking to improve thermodynamic efficiency, why are we talking about compression? Why are we talking about horsepower? Neither of things have any direct connection to head cooling.

That's not true. Theoretically otto cycle thermal efficiency is proportional to 1-(1/CR^0.4) or so.

Technically for best efficiency you want to optimize the temperature of the heads etc. to minimize heat transfer from the combustion process to the outside environment. From a thermal efficiency perspective, head cooling is considered a necessary loss (just like needed a TB is a pumping loss, etc.).