Are the horsepower #'s given by car companies wheel HP or Crank HP?

Answer 1

It's usually given as the gross crank or "shaft horsepower".

Gross horsepower is a measurement of engine output, taken at the flywheel, without the engine installed in a vehicle. Since the engine has no load on it, all of its energy can be used for making horsepower. Wheel-driven horsepower, by comparison, is a measurement taken at the driven wheels of a vehicle on what's called a dynamometer. This is done by placing the vehicle's driven wheels on a large roller and accelerating the wheels up to redline in first or second gear. Obviously, some energy is always lost between the engine and rear wheels (friction, etc), so the true useful HP is always less than what the car manufacturers advertise. Torque at a given speed as listed in the cars specs is usually a much more accurate indication of engine power, but most people don't know how to interpret these charts.

Answer 2

In general all the car companies use the same tricks to come up with their HP numbers. If they are trying to push it to the extreme they tout the HP of the engine. Those numbers are based on an engine not being in the car itself but rather hooked up to dynamometer to measure the HP of the engine. You can't really fool the machine or fudge the numbers unless you happen to leave off things like smog control (which Mazda did once when touting a Miata engine, the engine with actual smog control on was I think 10 or 15 HP less). The only things that can really be done to cheat the machine are the add-ons... if they run the engine with no power steering pump/ac compressor/alternator then it will be much more powerful than if are on the engine when it is tested. You could always test the engine with a battery and no alternator and get get a pretty decent jump just from leaving that part off. Of course those numbers are really meaningless when it comes to how the car performs since HP at the engine is always cut by the time it gets to the actual wheels. Cars that might weigh the same will not perform the same even when the engines have identical HP because the variables between the engine and the rear tires are so great. The transmissions will eat up some power... the weight of the rims will eat up some power... the weight of the brake rotors will eat up some power... ever thing that turns between the crank shaft of the engine and the tires will rob you of a little more power and those things vary from one car to another... In fact you have to consider other things like power steering, air conditioning as potential HP killers... that little extra belt to turn the power steering pump is also sucking away a bit of power just as the belt turning the AC compressor (even when it isn't turn on its still taking up a tiny bit of power to move the belt). In the end I dont think the companies are lying about their HP numbers, they are all just using the most agressive ways to measure it which are probably all equally meaningless to the driver that buys the car. I never really put much faith in the HP numbers. A more meaningful number that magazines list is are the 0-60 times. comparing those from car to car gives a better measure because it can't be doctored by the engineers.

Answer 3

Crank HP. There are too many variables for wheel hp. What gear's it in, diff ratio, what size and how heavy the wheels, what kind of gear oil, you'd never figure it out. Wheel hp is always much lower.

Answer 4

both. assume it's crank unless they are specific. because this number will be higher and looks good in ads and brochures. when being specific, such as in testing or in comparisons, they are all supposed to use rear wheel numbers. if i wanted proper hp numbers i would not rely on the individual companies but rather independent testing. car and driver magazine for example will give honest rear wheel horsepower numbers. good luck.

Answer 5

ISO is shaft HP
And is calculated in an adiabatic system where there are no external extractions,
It is an engine running at the correct temperature without water pump alternator or power steering or air conditioning and without a clutch pack or drive belts either.
So no power sapping accessories

Answer 6

Rear wheel

Answer 7

i thought wheel but if you take a car to the dino it will almost never be as much as they say.

Answer 8

whp