transonic.jpgWell-known Silicon Valley investor Vinod Khosla has never been shy expressing his opinion. Khosla once dissed plug-in hybrid vehicles — supported by environmentalists because of their partial reliance on batteries versus oil — as “nice toys …not material to climate change.”

Coming from Khosla, who has been among the most prolific investors in green technologies, the comments raised some eyebrows. However, the tune has since changed, because Kholsa has backed a select kind of hybrid vehicle after all (see our post).

Still, Khosla (pictured here) is clearly betting that combustion engines will stick around. The latest evidence is Khosla Ventures’ increased investment in Transonic Combustion, a company that says it will have a 100 mile per gallon sports car on the road by the end of this year.

khosla5.jpgTransonic focuses on a single part of an engine, the fuel injection system, to give a big boost to efficiency. Although secretive about details, the company says it can achieve extremely high compression ratios within engines and reduce the amount of energy lost to waste heat.

The proof of the unlikely-sounding boost to 100mpg is slated to be a lightweight demonstration stock car that Transonic plans to put out for a spin sometime in the third quarter. That probably means normal cars would get a somewhat lower fuel efficiency, using the same engine. However, anything over 50mpg would be an incredible gain.

For perspective, consider that in the 20 years between 1980 and 2000, the average passenger car went from 15mpg to only 22mpg. The Toyota Prius, a hybrid combustion / electric, only gets about 50mpg.

Although the size of Khosla’s latest investment was not disclosed, it does make the firm Transonic’s largest shareholder. For more on another recent Khosla Ventures investment in transportation, see this post on EcoMotors, a maker of hybrid diesel engines.