Variable Compression Ratio?

[TheNeedForZ]

I was thinking there could be a device that raise the compression on a turbo car when the boost is not on. Then I think "forget it, it's only going to be too complicated"

 

Then how about variable compression ratio for a car that can switch between high compression/high octane weekend car and mild compression/87 octane daily driver?

 

The compression raising device itself...I was thinking maybe a dead plug like a spark plug that is flush with internal combustion chamber surface when compression is in the "high", then the plug can be backed out to lower compression. The plug and hole edge in the chamber will be smooth of course.

 

Comments?

[Guest Battle Pope]

When I hear the words, "Variable Compression Ratio" my mind immediately locks up and my brain cells individually assume the fetal position.

 

Of course, I'm no machinist but if there were an easy or cost effective way to do it I'm sure it would have been done.

[JMortensen]

SAAB had a variable compression ratio engine a while back. I think it was just a concept car thing, never made it to production. IIRC the head hinged at one side and it would lower down to increase the compression ratio.

 

Did a quick search online came up with this: http://www.popularmechanics.com/automotive/auto_technology/1266656.html

[TheNeedForZ]

I read the link and it is a very neat idea, 225 HP and 224lb-ft from a 1.6 liter engine(with electrical supercharger) is pretty decent. It does the varying with just 4 degree of tilting...probably because the engine has such small chambers (1.6L 5-cylinder) I also realize that variable valve timing alters the dynamic compression ratio. Just wanted to know if there's a low tech way to do it.

 

Thanks for the link by the way.

[Phyxius]

I believe water injection can increase compression ratio, although I'm not sure that you wouldn't lose more power vaporizing the water than you gained from the extra compression. Someone more knowledgable on the subject could probably help.