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-   -   Mazda's engine development (http://forums.pelicanparts.com/off-topic-discussions/1003643-mazdas-engine-development.html)

Tervuren 11-28-2019 01:01 PM
Quote:
Originally Posted by unclebilly (Post 10672616)
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 11-28-2019 01:59 PM
Quote:
Originally Posted by Sooner or later (Post 10672675)
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 11-28-2019 03:06 PM
Quote:
Originally Posted by stevej37 (Post 10672658)
repost: selectable squish

http://forums.pelicanparts.com/uploa...1574962080.jpg

snip... nline-four demonstrator can adjust its compression ratio from 8.8:1 to 12.0:1 in 0.2 to 0.6 second.
Quote:
Originally Posted by stevej37 (Post 10672933)
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 11-28-2019 04:18 PM
Video at link.

Says it changes due to combustion and inertia forces.


https://vcr.fev.com

petrolhead611 11-28-2019 11:04 PM
Atkinson cycle does it by opening the inlet valve again when it would be shut in an Otto cycle

island911 11-29-2019 10:43 AM
^^
per WIkipedia
Quote:
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.


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