[missileman120]

Interesting article I found regarding horsepower. Some of you may have seen it before, others may not. I always cringe when people talk about horsepower as though it is the end all gospel of vehicle performance. I'd like to read more articles like this, so if any of you have some to share please feel free to post up. I'd like to be as prepared as possible the next time someone asks me the asinine question I put in the title.

Horsepower vs Torque

 

[lotusdriver2001]

Yup. Get the same annoying question all the time. Usually I tell them I don't know. If you measure it every day you'll get a different answer. Sometimes they like to push it and then boast of their brother's 800 HP Camaro or something. (I've never had such interacrions with owners of exotics for some reason.) One particularly obnoxious fellow got a bit disturbed when I asked him if every time he went camping, in stead of enjoying the trip and the campfire, all he coud do is sit around discussing the size of his manhood. Ya'll can have all the HP you want but if you can't use it it's no good.

Just try to placate them and move on. If you can figure a way to get a giggle out of it.... bonus points.

 

[Julian73]

Excellent. Also it is the work under the rpm curve that accelerates a car. The only thing dependent on an actual Hp figure is top speed, as the is the equilibrium point of power applied vs power resisted (wind and air drag, friction, rolling -sliding of tires and gear-bearing drag, assuming gearing rpm range permit reaching the balance point.

 

[dmpriso]

RPM in conjunction with torque is horsepower. So talking about torque over the RPM band is similar to talking about horsepower over the RPM band. Torque as a number by itself is completely meaningless. Most cars do have a gearbox.

Horsepower by itself also doesn't tell the whole story but if you try to accelerate very hard you will always be around the RPM of maximum horsepower.

 

[Julian73]

Actually max acceleration is at point of peak torque. Or more correctly after adjustment of curves to deduct power required to maintain the steady speed that one is going, the torque that is left over is the accelerating force.

 

[idolman]

HP to weight ratio, is the determining factor. Torque is part of it but not a major player in my limited opinion. Motorcycles have a great hp/weight ratio that's why they do well in acceleration vs cars (from experience). A car that weights 2000lbs with 300hp will beat a car that weights 4500 with 550hp 0-60-1/4 mile. My "limited opinion" is the Evora needs 400hp to be a nice "entry level supercar", to be a "Top Production Supercar" it needs 450+hp and a bit wider tires. Again my limited opinion

 

[Scottycali4nia]

I tell them how it is. I say given the current power to weight of my car, it's about the same as having a 500 HP "regular sized" car. It's about as quick as a base Gallardo.

If they're car guys, I'll tell them what the actual hp and torque is with a list of the mods that got me there, but regular non-car people... I stick with the above line. =] Usually works really well.

 

[jet37ski]

I like Ross Bentley's explanation (which I'm probably screwing up here but it's something close to Torque makes you accelerate and Horsepower keeps you there.

 

[Alek]

As we all know, torque or HP is not worth much if the weight is high.

The best way to describe the power characteristics of a car would be to show an acceleration curve from a rolling start thorugh all gears until top speed. That would compensate for all kinds of variables such as weigth, drag, grip, gearing +++.


Should be a simple thing to do in 2014...

 

[addertooth]

Some of these comments are killing me. HP is a unit of work. It takes work to accelerate or to maintain speed. Torque is not a unit of work, but it is (along with RPMs) used to calculate HP. 200 foot pounds of torque at 1000 RPMs, accelerate a car at the same G's as 100 foot pounds at 2000 RPMs. Overall acceleration (assuming same gearing/weight/drag) is affected by power under the curve. A higher RPM engine has a longer "area under the curve" than a low RPM engine.
Assuming both of the engines (below) are swapped into the same car, and torque is flat:
A 150 foot pound engine which can spin to 8500 RPM, is better than 200 foot pound engine which hits the rev limiter at 4500 RPMs. Torque alone is not the full picture.

 

[darkSol]

HP to weight ratio, is the determining factor. Torque is part of it but not a major player in my limited opinion. Motorcycles have a great hp/weight ratio that's why they do well in acceleration vs cars (from experience). A car that weights 2000lbs with 300hp will beat a car that weights 4500 with 550hp 0-60-1/4 mile. My "limited opinion" is the Evora needs 400hp to be a nice "entry level supercar", to be a "Top Production Supercar" it needs 450+hp and a bit wider tires. Again my limited opinion

Math is a bit off...

2000lbs @ 300hp = 6.67 lb/hp

That's the same as:
2500lbs @ 375hp
3000lbs @ 450hp
3500lbs @ 525hp
4000lbs @ 600hp
4500lbs @ 675hp
...

 

[aschen]

I didnt read the article, but hopefully it is technically correct. This is one of the most debated issues on the internets. We have done it a few times here even. I think it is guys like carol shelby saying things like torque wins races, HP sells cars, and other cute but physically nonsesical statments that confuse people.

also the engineer in me cant go without pointing out the semantics. Horse power is a unit of power not work. Work is synonymous with energy. Power is the rate of work flow.

If you integrate, or add up over time, hp you end up with work done. In they end power is what makes cars fast, provided it can be geared appropriatly.

 

[idolman]

Math is a bit off...

2000lbs @ 300hp = 6.67 lb/hp

That's the same as:
2500lbs @ 375hp
3000lbs @ 450hp
3500lbs @ 525hp
4000lbs @ 600hp
4500lbs @ 675hp
...

Right. "beat" as in faster 0-60 / 1/4 mile vs a heavier higher hp car. Wasn't making a presentation up and down the scale.

But here is a nice semi accurate comparison (without scaling to a precise decibel point)

I believe i read the Evora is 8.7 hp/weight comparison?:
A new corvette (3500lbs) think i read 5-ish per pound?
A newer Mustang (3600lbs?) maybe almost 7-ish per pound?

Thus a corvette blows the doors off an Evora S (350hp/3200lbs) 0-60 and 1/4 mile on acceleration
A Mustang eats its lunch too.

Without to much argument, the Evora needs a bit more kick, 400hp would be nice in the acceleration dept.

and im still wondering why my Evora window wiper switch seems to have a rear window wiper control (is that what it is?), can seem to find the wiper. anic:

 

[aschen]

If you have 2 cars with the same power to weight ratio, in general:

The lighter car will be quicker at lower speeds due to higher tire traction to weight ratio

The heavier car will be quicker at higher speeds due to higher power to drag ratio

 

[pray4mojo]

HP = Torque x RPM ÷ 5252

/thread

 

[Julian73]

HP = Torque x RPM ÷ 5252

/thread

Which brings us back to post #1

 

[pray4mojo]

Which brings us back to post #1

HP dictates how fast you hit the wall.
Torque dictates how hard you hit the wall.

//thread

 

[anthonyseven]

HP dictates how fast you hit the wall.
Torque dictates how hard you hit the wall.

In other words:

:shift: