you should be able to tell at what temps in celsius when the fans kick in. for me the file would be appleblower.component in system/library/extensions. i would be extremely catitious doing this though. i'm thinking about lowering the temp at which the fans kick in. i'd rather have a louder mbp than hot comp.
ok i have done some more investigating. Their are two files in my mbp, should be the same for you though. One controlls the temps at which the fans turn on and at what speed they run at. I want you to check if you have a file called Appleblower.kext and one called Applefan.kext under system/library/exetensions.