Variable compression 1

[enginesrus]

https://www.youtube.com/watch?v=ZUXENUsPqh0

https://www.youtube.com/watch?v=DdM2VbbdtB4

 

[enginesrus]

Hmmm I should have patented my idea 20 some years ago.

 

[berkshire]

If you can demonstrate prior art, depending on the country where the patent was filed , you may be able to invalidate their patent.
B.E.

You are judged not by what you know, but by what you can do.

 

[tbuelna]

Nissan has been working on the VC concept shown on that Infiniti engine for at least a decade, and has probably filed over 50 patents covering the idea.

 

[TugboatEng]

What is the benefit?

 

[BrianPetersen]

Allows the engine to operate at a higher compression ratio (for better thermal efficiency) under conditions when it is possible and advantageous to do so (generally, at part load - which, in automotive applications, is generally most of the time).

 

[turbomotor]

Continental Motors and BICERA demonstrated variable compression ratio for TACOM back in the mid 1970s. The technology worked (to a degree) but the complication did not lend itself to production military engines. Also, the government wanted a turbine in the M1.

 

[turbomotor]

Forgot to add link.

http://papers.sae.org/760051/

 

[TugboatEng]

It seems to me that not bringing the piston all of the way to the top of the cylinder would have very negative impacts on expansion ratio and squish. Variable valve timing can also be used to control compression ratio while still maintaining a tight squish clearance and high expansion ratio.

 

[Lou Scannon]

Variable valve timing can also be used to control compression ratio while still maintaining a tight squish clearance and high expansion ratio.

That's very much the idea with VVT Miller cycle optimized engines. They do leave a little power density on the table vs engines that are optimized for high voleff at full load, other constraints such as emissions notwithstanding.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[BrianPetersen]

I have the same concerns about lack of squish when operating in low-compression mode. Squish is not the only means of arranging for charge motion, though.

 

[TugboatEng]

That is why essentially all diesel engines over 50 hp run 4 valve heads, for the turbulence.