[rcracer_tx]

As the title sates, the standard measurement for horsepower and torque on new cars are rated at the crank which does not take into account drivetrain loss. Why wouldn't the standard be to show average WHP and WTQ for a car?

This would show how efficient the drivetrain is, and show how much power is actual available in the car. Just seems like a poor rating system when a car that makes 380hp with an efficient drivetrain can put as much power to the ground as a 400+ hp car with a crappy drivetrain. Opinions?

[amgthis]

Higher numbers sound better?

[wj4]

Advertising purposes, I would guess.

[Sniz]

its always been HP at the crank as far as I can tell.....goodluck changing that.

People who know.......for example more of the people on enthusiast forums, know that whp is all that matters.

[D_o_S]

I don't think it has always been that way... didn't the Chargers in the past show a drastic decrease in power because HP started being measured at the wheels instead of the engine? After a while I think they reversed it back...

[rcracer_tx]

^ Not Sure

Are the numbers on the window stickers of a car controlled by the government?

[imported_mega]

Originally Posted by D_o_S

I don't think it has always been that way... didn't the Chargers in the past show a drastic decrease in power because HP started being measured at the wheels instead of the engine? After a while I think they reversed it back...

for a while they were under rating cars drastically to get around government regulation

that was back in the late 60's early 70's before the bad years

[ENINTY]

The test is a SAE standard test so that all engines are tested identically and therefore can be compared to each other. The drivetrain measurement is not an identical test, as drivetrain design affects the amount of power loss at the drive wheels. In other words, testing the power at the wheels of a RWD, FWD, AWD (with auto/manual/or CVT transmissions) would show no correlation of power production between the drivetrain types. All engines, regardless of design, test the same when HP and torque are measured at the crank.

[jeremyc74]

Chassis dynos are relatively new compared to engine dynos. They were invented for tuners so they don't have to pull the engine out of the car to be able to test the power levels. Chassis dynos are also more variable than engine dynos. Engine dynos have been around more than 60 years, and they're what's used as the engine is being developed and tested.

Chassis dynos are great for tuning, but I doubt the manufacturers ever switch to publishing WHP numbers instead of crank.

[Sniz]

Originally Posted by imported_mega

for a while they were under rating cars drastically to get around government regulation

that was back in the late 60's early 70's before the bad years

take the ZL1 camaro for instance.......

[BMW_TT]

Marketing

[jeremyc74]

Originally Posted by BMW_TT

Marketing

It has nothing whatsoever to do with marketing. Flywheel HP is the standard that has been used for 100 years.

[flyinb501]

Originally Posted by ENINTY

The test is a SAE standard test so that all engines are tested identically and therefore can be compared to each other. The drivetrain measurement is not an identical test, as drivetrain design affects the amount of power loss at the drive wheels. In other words, testing the power at the wheels of a RWD, FWD, AWD (with auto/manual/or CVT transmissions) would show no correlation of power production between the drivetrain types. All engines, regardless of design, test the same when HP and torque are measured at the crank.

This is the correct answer. Testing must be identical for all ENGINES so comparisons can be made.

[philaf_666]

Even with WHP and WTQ, same numbers on two different engines won't produce the same results depending where on the power band are those HP and TQ.

Take the M3 and 135i... the engine curves are very different. More WHP doesn't necessarily make a car faster. A what about the weight?

So for me, it will always be nothing but numbers.

Numbers coming from tests on a closed track will prove better.

[ENINTY]

Originally Posted by imported_mega

for a while they were under rating cars drastically to get around government regulation

that was back in the late 60's early 70's before the bad years

What he is referring to is when the SAE changed the test from Gross horsepower to Net horsepower. In the 60's during the HP wars of muscle cars, manufacturers used to measure engine power without any accessories (power consumers) such as alternators and pumps and street exhaust headers. They changed the test to net horsepower to show what the horsepower would be as if the engine were operating in the car. I believe the change was made in the late '60s.

[BMW F22]

Originally Posted by ENINTY

The test is a SAE standard test so that all engines are tested identically and therefore can be compared to each other. The drivetrain measurement is not an identical test, as drivetrain design affects the amount of power loss at the drive wheels. In other words, testing the power at the wheels of a RWD, FWD, AWD (with auto/manual/or CVT transmissions) would show no correlation of power production between the drivetrain types. All engines, regardless of design, test the same when HP and torque are measured at the crank.

What he said- I was going to guess something along those lines as well.

[rcracer_tx]

Originally Posted by ENINTY

The test is a SAE standard test so that all engines are tested identically and therefore can be compared to each other. The drivetrain measurement is not an identical test, as drivetrain design affects the amount of power loss at the drive wheels. In other words, testing the power at the wheels of a RWD, FWD, AWD (with auto/manual/or CVT transmissions) would show no correlation of power production between the drivetrain types. All engines, regardless of design, test the same when HP and torque are measured at the crank.

My point was that a crappy inefficient transmission on a high HP car will sell more because it is a higher number, even though it can not put that amount of power down to the because the drivetrain. Measuring torque and horsepower at the wheels would be a much more accurate reflection of the perforce of the car...

The best indicator of straight line performance would be weight per whp and weight per wtq?

[BMWeber]

Originally Posted by rcracer_tx

My point was that a crappy inefficient transmission on a high HP car will sell more because it is a higher number, even though it can not put that amount of power down to the because the drivetrain. Measuring torque and horsepower at the wheels would be a much more accurate reflection of the perforce of the car...

The best indicator of straight line performance would be weight per whp and weight per wtq?

It would be an interesting not sure about accurate. a chassis dyno has so many more variables it could be even more skewed then comparing power to weaight from the fly wheel. not to mention the difference in dyno manufacturers. maybe if they came up with a standard environmental conditions and used a dynapack (http://www.dynapack.com) style dyno you could come up with some amount of consistency. but the auto makers will probably never do anything like that. all of a sudden on year a car is rated at 300 next year the car is 270. not to mention 97% of the auto buyers couldn't care less about WHP vs fly wheel HP

[SteveMD]

Originally Posted by ENINTY

What he is referring to is when the SAE changed the test from Gross horsepower to Net horsepower. In the 60's during the HP wars of muscle cars, manufacturers used to measure engine power without any accessories (power consumers) such as alternators and pumps and street exhaust headers. They changed the test to net horsepower to show what the horsepower would be as if the engine were operating in the car. I believe the change was made in the late '60s.

I think it was 73-74.

[footie]

Originally Posted by ENINTY

The test is a SAE standard test so that all engines are tested identically and therefore can be compared to each other. The drivetrain measurement is not an identical test, as drivetrain design affects the amount of power loss at the drive wheels. In other words, testing the power at the wheels of a RWD, FWD, AWD (with auto/manual/or CVT transmissions) would show no correlation of power production between the drivetrain types. All engines, regardless of design, test the same when HP and torque are measured at the crank.

Correct, there is far to many combinations and variables to take into account. But in reality does any of this really matter, surely it's the performance figures that determine all of the above.

The same thing is true for official economy figures, a different driving style and route will show up a different result.