I assume that rwhp means rear wheel hp but am not sure. Can anyone please elaborate on this? Is rear wheel hp a more specific measure of a cars hp? And what is an average stock S2000 rwhp?

Appreciate the help. Thanks.


Hobb

 

A stock S2000 is supposed to have 240 HP to the crank (no transmission, driveshaft, etc.). To measure the HP of a car after it's assembled, you measure the HP at the rear wheels. Depending on the break-in, age, temperature, etc., a stock S2000 should have around 200 HP to the wheels. Every dynamometer (sp?) also gives different results.

 

Usual Horsepower figures are guesstimates from the engine. I forgot the equation but its like engine torque times some number equals horsepower. RWHP is a number generated at the wheels, usually on a dyno. It factors in drivetrain loss and is usually about 10-20% less than engine horsepower, depending on which wheels are driving. RWHP is not a more specific measurement, just a more accurate one in terms of real world performance. An even better measurement of performance is a car's Horsepower/weight ratio and Torque/Weight ratio.

Phi

P.S. Feel free to correct me anyone.

 

[QUOTE]Originally posted by Phi2k
[B]Usual Horsepower figures are guesstimates from the engine.

 

Here's the general formula for horsepower:

Hp = (rpm x torque) / 5,252
torque = Torque = (5,252 x hp ) / Rpm

more readings: http://www.stanford.edu/~voloshin/lhowwhy.html

 

Horsepower numbers claimed by manufacturers are always numbers produced at the engine. "Flywheel Horsepower", basically there are engine dynos, and there are chassis dynos, one if where you run the engine outside of the car, that will give you the most accurate power numbers. The other is where you have a complete car and you ethier set it up on roller(s), or hook it up to the wheel hub and you check power.

A chassis dyno (rwhp) is what power you make to the ground, and an engine dyno is what you make at the engine. There is a loss delivering power to the ground from the engine, this is drivetrain loss. You can improve the efficiency of the drivetrain by reducing the weight, and swapping parts with improved parts, such as the clutch disk, pressure plate, or differential.

The S2000 has approx 15-17% drivetrain power loss. Front wheel drive cars have about 10% drivetrain loss, and all wheel drive cars have about 20-25% loss.

Honda apparently rates their engine from the least common denominator of a sample set of engines they make. This is the opposite of what most other car manufacturers do, where they rate their engines from the most powerful from a sample set of engines. I believe Chevy and Ford do this?

Chris

 

[QUOTE]Originally posted by Indecision
[B]Here's the general formula for horsepower:

Hp =

 

look at their torque curves and it will tell all. If their horsepower isn't that high, then the curve probably drops as it approches higher rpm.

 

Actually HP is a calculated number (Tq and RPM) where torque is what is actually measured.

 

I may be looking at this equation wrong, but if it is correct, won't the HP curve and Torque curve ALWAYS cross at 5252 RPMs?