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

[Beebo Kanelle]

Thank you one and all.

I'm afraid I wasn't clear enough in my original inquiry -

I am modeling the Type 4 based upon other engines I have been involved with in the past.

I am not, however, familiar enough with the air-cooled engine to know if there are any hidden constraints that are unique.

I believe it is possible to increase the output to 100 - 110 hp / liter in a street driven, smooth idling engine of two valve design - but I know there are limits -

and it appears that, without going to exotic extremes that the reasonable limits would be 13:1.

Has anybody gone higher ?

Any and all info is greatly appreciated

Thanks for the input / advice / sage wisdom

[Bulldog9]

Thank you one and all.

I'm afraid I wasn't clear enough in my original inquiry -

I am modeling the Type 4 based upon other engines I have been involved with in the past.

I am not, however, familiar enough with the air-cooled engine to know if there are any hidden constraints that are unique.

I believe it is possible to increase the output to 100 - 110 hp / liter in a street driven, smooth idling engine of two valve design - but I know there are limits -

and it appears that, without going to exotic extremes that the reasonable limits would be 13:1.

Has anybody gone higher ?

Any and all info is greatly appreciated

Thanks for the input / advice / sage wisdom

A few thoughts from a novice 1 time Type 4 builder.

100-110HP/liter is not doable in a N/A Type 4 without a SERIOUS cash infusion, unless perhaps it is an alcohol burning bracket racer you rebuild after every run. That's optimistic even for a modern N/A inline 4 street motor....

I have two liter+ motorcycles that make this kind of power, but at 8-10K and no torque. Not a problem to push 700lbs, big problem for a passenger car.

I'm sure it can be done, and maybe has, but after spending the last 5 years watching, reading, learning and doing, I havent seen it..... The Type 4 is a different animal.. Do some reading and educate yourself. The CR is not really low for that era. 13:1 CR reasonable? you need to put down the crack pipe freind (IMG:style_emoticons/default/drooley.gif)

[Mark Henry]

I'm sure it can be done, and maybe has, but after spending the last 5 years watching, reading, learning and doing, I havent seen it.....

Jake says he's done it, closest I've come on a slightly milder 2.6L build is 70hp/liter, but you're totally right on outrageously expensive and not a novice build.

Personally for the novice I'd start with a 2056cc build and if you are truly skilled a 2276cc would be the max. Both engines are great in a 914.
BTW just a FYI a performance /6 build is way harder than a /4. BTDT