Ruiz..
there are A LOT of different factors..
Figures release from automotive companies is called BHP (brake horse power)
this is a figure based on the SAE standards.. that tests the engine in optimum temperatures, in perfect conditions, with a bare naked engine... I mean no power steering, no flywheel, no fan, no power accessories running.. nothing.. its literally crank horsepower in perfect conditions.
A good universal figure is 20%. I've always been skeptical since every car is different.. no 2 machines are identical. On top of that FWD will have less drivetrain loss because the transmission and differential are all in one, with no super long driveshaft to lose power in. RWD figures are next on the list.. with more drivetrain loss then FWD, but less then AWD... AWD cars have to transfer the power to the front transaxle, then a driveshaft, then another differential..
the same car with 18" wheels will put out less HP and Torque then the same car with 13" wheels and small tires on a rolling dyno. EVERYTHING makes a difference... everything.
Also here in colorado at nearly 6,000 ft above sea level.. the performance of a car is terribly sacrificed. during my studies of aviation in college we learned a general rule of thumb to cut nearly 15% of the available power at 8,000 ft above sea level. thats 15% freakin percent, in addition to the general 20% powertrain loss.
Thats a 35% loss at this altitude... so that advertised 270bhp nissan 350z actually puts out 175.5 wheel horsepower in PERFECT conditions.
the pressure in the atmosphere, the air temperature.. air density.. dew point.. everything makes a difference..
some days in the summer we have a density altitude of nearly 9,500 ft in July.. which means im physically standing at an altitude of 5,200 ft but the air density on a hot day is similar to 9,500 ft because the air is so thin. now increase that figure to nearly 40-45% power loss.
Catch my drift?