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]

guys! I didn't mean to start a firestorm over this... I was just curious as to what the mechanical limitations of the type 4 engine was

no secrets here.

as for the concept, its a variation of the Atkinson / Miller cycle.

On circular intake ports it seems to be possible to minimize the pumping losses while taking advantage of a much greater expansion cycle. for example, instead of 1-2 pts, utilize 5-7 pts, allowing for a cooler exhaust and broadening the torque curve.

Years ago I took my Audi 5000 turbo and increased to CR to 11:8 +- while altering the cam timing events so the actual CR was 8:1 - that is my reference point - variations on this theme have been done to jaguar engines and a domestic v8 - all liquid cooled

I bought a 914 when I started having more time, and have become intrigued with the Type 4 engine.

as far as the modeling, right now its computer - and I'll see where that leads me.

[Mark Henry]

guys! I didn't mean to start a firestorm over this... I was just curious as to what the mechanical limitations of the type 4 engine was

no secrets here.

as for the concept, its a variation of the Atkinson / Miller cycle.

On circular intake ports it seems to be possible to minimize the pumping losses while taking advantage of a much greater expansion cycle. for example, instead of 1-2 pts, utilize 5-7 pts, allowing for a cooler exhaust and broadening the torque curve.

Years ago I took my Audi 5000 turbo and increased to CR to 11:8 +- while altering the cam timing events so the actual CR was 8:1 - that is my reference point - variations on this theme have been done to jaguar engines and a domestic v8 - all liquid cooled

I bought a 914 when I started having more time, and have become intrigued with the Type 4 engine.

as far as the modeling, right now its computer - and I'll see where that leads me.

as for the concept, its a variation of the Atkinson / Miller cycle.

(IMG:style_emoticons/default/huh.gif) (IMG:style_emoticons/default/laugh.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/av-943.gif)

The type 4 engine is a 50 year old 2 valve pushrod design based on a 85 year old 2 valve pushrod design. Add to this that the Type 4 has weak head sealing/bolt design for turbo or supercharging at anything but moderate levels.
The thing is unless you have made a amazing Type 4 flux capacitor breakthrough, what you are talking about would be better off started on a clean slate.

There has been all kinds of theoretical engine discussion here over the years. Not once has anything come to fruition that hasn't been already been firmly rooted in current or past technology.
Computer modeling can be great, but the Type 4 is oldschool, try building a couple of real T4 engines first. Then get back to us with some theories.

PM member veekry9, he would be a perfect muse, who knows maybe the two of you can make an amazing breakthrough. (IMG:style_emoticons/default/smile.gif)