Mazda's engine development

[Tervuren]

Originally Posted by unclebilly

Wasn’t Porsche the first to market a variable compression spark ignition gasoline fueled car? Sometime in 1975???

Anything with a turbo is variable compression...

I think he meant compression ratio, which will generally be the difference in the combustion chamber capacity from BDC to TDC.

[stevej37]

Originally Posted by Sooner or later

I bet that puppy ain't cheap.

Probably right! I wish the article would have gone further and explained what controls the miniature pistons that rotate the cam. Oil pressure? Electronic?

[island911]

Originally Posted by stevej37

repost: selectable squish



snip... nline-four demonstrator can adjust its compression ratio from 8.8:1 to 12.0:1 in 0.2 to 0.6 second.

Originally Posted by stevej37

Probably right! I wish the article would have gone further and explained what controls the miniature pistons that rotate the cam. Oil pressure? Electronic?

Oil pressure. Note the long slot in the main.

edit: internal passages must feed (selective) pressure up from the main bearing.
I can see how this could hold pressure (like a hydraulic valve) but I'm not seeing the control side.

[Sooner or later]

Video at link.

Says it changes due to combustion and inertia forces.


https://vcr.fev.com

[petrolhead611]

Atkinson cycle does it by opening the inlet valve again when it would be shut in an Otto cycle

[island911]

^^
per WIkipedia

In the late 20th century, the term "Atkinson cycle" began to be used to describe a modified Otto-cycle engine—in which the intake valve is held open longer than normal, allowing a reverse flow of intake air into the intake manifold. This "simulated" Atkinson cycle is most notably used in the Toyota 1NZ-FXE engine from the early Prius.