Difference in horsepower rating systems, couldn't find anything that identified a US-specific horsepower definition, but the table on this page shows differing conversion calculations depending upon the specific type of horsepower:

http://www.simetric.co.uk/si_hij.htm

Difference in pound measurement between the US and UK, which I assume would affect the calculated torque (express in lb/ft) for cars in each country:

http://uk.answers.yahoo.com/question...8053729AAnHU6A