[raj_5004]

Originally Posted by mithun

Why some cars are having flat floors & others are having very high bulge ?

i think it depends on the design of the underbody mate. for e.g. look at SUVs. they have a seperate chassis unlike cars. this allows for ample room below it's floor to incorporate the mechanisms. cars dont have a chassis and also their floor is too low. hence the bulge.
these days, modern technology allows for offset crankshafts which is possible due to "hypoid gears". this gives the designers more space under the car body and hence it need not bulge into the car cabin.