Windsor-based Thermodynetics , which owns the Turbotec lines of heat transfer technology for automobiles, made an initial public offering on the London Stock Exchange last year and has been putting that capital to frequent use by upgrading facilities, making new hires and developing a new line of Turbotec products. Revenue responded with a 25 percent jump for the company’s fiscal year, which ended March 31. But to this point, the income isn’t outpacing the spending, as gross profit margins fell 23 percent in 2007, a situation the company says is being addressed.