Question about Horsepower and Torque (Sorry if Long)

[FaytalsCamaro]

Hello, I was hoping you guys would be able to explain something to me that i have been wondering lately. I keep hearing the phrase that Torque wins races. Which is totally understandable. The more torque your able to generate the faster off the line you are capable of. If you can put that power to the ground.

Also another noteworthy quote is Torque is what you feel, Horsepower is what you read about. Which again is understandable. What i dont understand is WHEN does horsepower come into effect in a race? I know Horsepower is the result of an equation that includes torque.

HP= (torque * RPM) / 5252

So with that logic HP has to come into effect at some point right? Lets use 2 cars as an example. The 2009 Mustang GT and the 2012 v6 Camaro.

Camaro is looking at 323hp, with 278lbs of Torque

Mustang GT is at 300hp, with 320lbs of Torque

I use these two cars because of HP is more on one with Torque being less. If i knew of different vehicles more closely related i would use them.

Ive personally seen videos of some people beating older Mustang GTs with their newer v6s. But there are so many different factors that come into play. So lets make this a perfect world. Same driver, Ideal conditions and another big thing, SAME WEIGHT.

Im completely going to guess on this but according the the quote i mentioned first the GT would win the quarter mile. But when if at all would the camaro pass the GT seeing as it has more HP?

OR

is everything out the window at this point and Torque may not be able to win the quarter mile race for the GT?

[The IOM Ninja]

There is a lot more to factor in than just torque for how fast you will get off the line. There are cars with as around as much torque (BMW M3 for example) as the V6 Camaro that are nearly half a second faster than the SS 0-60 (SS is 4.5 with rollout, M3 is 3.9 with rollout).

From what I understand is horsepower affects top speed and acceleration, but to say that would be kinda false because gearing, transmission type, wheel width, sidewall height, rim size, and several other things have to be factored in as well.

Torque from what has been said on this site, and I'm slowly learning, is how much force you have to spin the wheels.

*Somebody please chime in to tell me if anything stated is off, Thanks*

[DGthe3]

This has come up a few times, so rather than re-state what I've said in years past, I'll just point you to some of the better threads on the matter & you can read whats already been said on the matter:

www.camaro5.com/forums/showthread.php?t=45264
www.camaro5.com/forums/showthread.php?p=173479

and there is also this, which is probably the best site I've seen for explaining how horsepower works. His other articles are pretty good too. craig.backfire.ca/pages/autos/horsepower

[KMPrenger]

I like this question.

What I think he is basically saying is using two exactly same vehicles...suspension, tires gearing, weight...everything.

Run one with 300HP, 320TQ....versus another 323HP, 278TQ. The one with more torque should obviously be quicker off the line, but at some point does the higher HP car pass it?

[Madness11]

There are too many variables still to be able to accurately give a response. Gearing in the transmission and rear end are the biggest factor. You can have it geared to take off from the line really fast but you have no top end speed or it is slower off the line but if fast on top end. THIS is where torque and HP come into play well partially. Th transmission and rear end can simply called power multipliers (power being torque and HP) to get the weight of the vehicle moving. The less you multiply (shifting up) the more power you require to maintain acceleration and top speed.

[FaytalsCamaro]

Originally Posted by KMPrenger

I like this question.

What I think he is basically saying is using two exactly same vehicles...suspension, tires gearing, weight...everything.

Run one with 300HP, 320TQ....versus another 323HP, 278TQ. The one with more torque should obviously be quicker off the line, but at some point does the higher HP car pass it?

This. Obviously it would have to be recreated in a perfect world. But even if EVERYTHING was the same on both vehicles when it comes to variables there is still no way to tell?

[GretchenGotGrowl]

First off, those numbers are just at peak. They change throughout the RPM range. Take two hypothetical cars are identical in every respect except:
Car A
------
300 ft-lbs @ 2500 RPM
250 ft-lbs @ 4500 RPM
Car B
------
250 ft-lbs @ 2500 RPM
300 ft-lbs @ 4500 RPM
Both would be represented as having 300 ft-lbs of torque. However, plug the numbers into your equation for HP. Which one do you think will get off the line quicker? Which one do you think will accellerate quicker from 4500 RPM to redline? Now think about gearing. If they are geared so shifting at redline in 1st lands you at 4000 RPM in second and shifting at redline in 2nd lands you at 4500 RPM in third, which one do you think will have the higher trap speed?

[wadeh]

There are lots of factors.

Assuming that you have gearing to optimally match the engine characteristics, I believe that horsepower is what you want. Put another way, torque at high RPMs is better than the same torque at low RPMs (because it makes more horsepower.)

Consider a Formula One car. Those engines don't make a lot of torque, but what torque they make is at ridiculously high RPMs. Also, they have really tight gear spacing, so they can keep the engine up in the power band all the time. As a result, those cars have surreal acceleration.

There is obviously more to it, but that's the idea.

[jmaynard]

Originally Posted by Madness11

There are too many variables still to be able to accurately give a response. Gearing in the transmission and rear end are the biggest factor. You can have it geared to take off from the line really fast but you have no top end speed or it is slower off the line but if fast on top end. THIS is where torque and HP come into play well partially. Th transmission and rear end can simply called power multipliers (power being torque and HP) to get the weight of the vehicle moving. The less you multiply (shifting up) the more power you require to maintain acceleration and top speed.

+1 but you also left out shifting patterns and gross vehicle weight. Both make a diffence off the line and vehicle weight also in long run.

[fielderLS3]

Torque is a unit of force. It is how hard the engine is capable of "pulling." Horsepower is derived from torque, and is a unit of power, the rate at which the engine does work, which is basically force multiplied by the rate at which the force is applied.

Ignoring frictional losses to keep it simple, the amount of force that is applied to the wheels to move the car is the engine's torque multiplied by the final gear ratio (which is the transmission ratio, multiplied by the differential ratio). The car's acceleration is that force divided by the car's mass. The engine that is producing more torque will accelerate faster given that the mass and the final gear ratio are the same.

Horsepower can be thought of as a quantity that saves you from having to make the torque/gear ratio calculations to determine which car is (generally) faster and which is not, as taking into account the speed of the engine essentially makes the gear ratio part of the calculation.

For example, if an engine A has half the torque of engine B, but engine A can make that torque while revving at twice the speed of engine B, they make the same horsepower. Engine A has half the torque to work with, but the car with engine A can have a gear ratio of double that of the car with engine B while traveling at the same speed. That makes the final force on the drive wheels the same (half the torque, but double the ratio), and if the speed the vehicles are traveling at is also the same, that means the power is the same.

This is basically the math behind it. In the real world, there are far too many variables to generate an all-covering rule of thumb. The amount of torque engines have varies with RPM. And every engine is different, making their peak torque at different RPMs, and making different percentages of peak torque at any given RPM. Every car will have different gear ratios as well.

[76z28]

Originally Posted by GretchenGotGrowl

First off, those numbers are just at peak. They change throughout the RPM range. Take two hypothetical cars are identical in every respect except:
Car A
------
300 ft-lbs @ 2500 RPM
250 ft-lbs @ 4500 RPM
Car B
------
250 ft-lbs @ 2500 RPM
300 ft-lbs @ 4500 RPM
Both would be represented as having 300 ft-lbs of torque. However, plug the numbers into your equation for HP. Which one do you think will get off the line quicker? Which one do you think will accellerate quicker from 4500 RPM to redline? Now think about gearing. If they are geared so shifting at redline in 1st lands you at 4000 RPM in second and shifting at redline in 2nd lands you at 4500 RPM in third, which one do you think will have the higher trap speed?

My corvette(geared less effectively) but lighter, ran a faster trap speed than the new v6 camaros and makes 50+ less horse than they do or something, but 350lbs of torque


Torque will get you ahead, but horsepower will keep you ahead

On the street torque will win(if you can get traction)

[GretchenGotGrowl]

Originally Posted by 76z28

My corvette(geared less effectively) but lighter, ran a faster trap speed than the new v6 camaros and makes 50+ less horse than they do or something, but 350lbs of torque


Torque will get you ahead, but horsepower will keep you ahead

On the street torque will win(if you can get traction)

That's why I said everything else was the same. You start factoring in things like gearing and weight it clouds the understanding of how torque and horsepower affect the outcome.