In doing research for a cam change for my C5, I noticed all the cam vendors and aftermarket installers advertise the maximum peak horsepower you MAY get by installing their specific cam. Some are pretty big, like a recent post about an 02 coupe with headers picking up 70hp. by just changing the cam

But, the same car gained only 26 foot pounds of torque. As I always understood, it was torque not horsepower that accelerated a car forward. Horsepower would relate to top speed, and torque to ¼ times and SOP acceleration. Advertised torque gains are always way less than hp gains.

So whats the story here? Why do peak hp numbers always seem to get glamorized? Am I wrong about the relationship between tq hp and acceleration?

 

BIG HP Numbers SELLS

torque WINS races.

 

Acceleration is proportional to power.

BUT, if you're not making decent low-rpm torque, you're only getting high power at very high rpm, where it's really only useful for drag racing. For street use and track racing, torque gives you the useful SOP acceleration at more reasonable rpm.

Peak power is glamorized because it's typically the bigger number, plain and simple.

If you can take a ride in a Viper, it will answer all your questions. My brother's GTS has "only" about 400-410 rwhp, which is about as much as a fully bolted-on and tuned C5 Z06. But he has nearly 450 ft.lbs of torque at the rear wheels, and the vast majority of that is available at 2500 rpm. It THROWS me to the back of my seat when he hits the accelerator!

 

one of my favorite quotes:

Understeer is hitting the wall with the front of the car.
Oversteer is hitting the wall with the back of the car.
Horsepower is how fast you hit the wall.
Torque is how far you push the wall after you hit.

 

 

An engine (or any other twisting mechanisim) can make xxxxxxxft/lbs of torque, but if there is no movement there will be no power numbers to show.

Power (HP) is a measure of twisting force x speed (or movement).

The faster you spin an engine the more power it will make, assuming that torque remains constant.

Torque however does not remain constant, as you notice how it builds up and then falls off at high rpm.

If you can maintain twisting force (torque) at higher rpms, you will see the "same" torque numbers, but because you have increasedthe engine speed you will now see much great HP numbers.

torque and speed are real, horsepower is just a measurement.

The key to picking a camshaft is to make sure you have the amount of torque that you want at the appropriate rpm level.

I hope this quick summary helps. Sorry, for it being so crude in explanation

 

...except I don't like this line because I think it is misleading for those who don't know any better - "torque and speed are real, horsepower is just a measurement."

Torque (rotational force), Speed (rate of change of position), and Power (rate of doing Work or using Energy) are all quantities and are all quite real. They can all be measured, and for American automobiles we typically use the units of foot-pounds, miles per hour, and horsepower to measure them, respectively.

I suspect you already know this, but I thought your wording was a bit strange.

 

Ya, , I know it was a crude attempt, but I'm at my desk typing between clients lol

Here was my thought in regards to "real" as I used it.

Torque is something you yourself can apply. Twist a cap off a bottle for instance.

Speed (engine rpm) is something you can see. How fast you twisted the cap off.

Horsepower is just a measure of torque applied in relation to speed of movement. It just a number, just a measure of work being performed.

Horsepower is not "real", it is not actually witnessed or created. Torque is created, and movement is witnessed, and horsepower is just the number given to the relation of those two "real" elements. Horsepower, as a measure, IS real, of course. But, it is only a measure of the 'real' elements that are being witnessed.




Yes, they are all measurements, but people tend to think that horsepower and torque can be compared, but they are just different.

Torque and engine speed are the only relevent concerns when building an engine. Sadly though, many will always associate the word "torque" with "low rpm's", but torque is present at all speeds. It just depends on where torque is focused at within the rpm range that determains HP at a given rpm.

Last words Horsepower is just a by-product of "torque applied". (torque applied = twisting force in motion)