Alright ive been thinking about this for a while, and im not sure how to explain this question. As i understand tq is the twisting force, and hp is how fast the tire spins (for lack of a better deffinition). However if you have 400hp and 0tq the vehicle will not move an inch, and if you have 0hp and 400tq it wont move either (correct me if im wrong).
So if that statement is correct then tq does have a direct affect on overall speed/ET's. I guess what im trying to say is that hp is overrated and tq isnt getting enough attention from your average street racer. This is mainly brought up because i have friends that build american cars as well as i have friends that build imports.
The imports constantly lose against american cars from my experience.
They always talk about power to weight ratio, however when i ask about power they almost never mention tq, and they always give me a shady answer when i ask about it. I assume that the american cars usually win because of the amount of tq they put out.
If anybody can follow what i just wrote then please clarify.

 

Torque is how much work you can do, and horsepower is how fast you can do it.

It's impossible to have 0 torque and anything other than 0 horsepower. It is also impossible to have 0 horsepower and anything other than 0 torque.

Horsepower = Torque times RPM divided by 5252.

 

There was a discussion here a long time ago about hp/tq...maybe you can find it by using my user name and the advanced search option specifying this forum....


But to make a few general statements....


Casey is 100% right in what he said but I'll elaborate a tad.

Horsepower is not a physical measure of a force. It's a calculated value of torque and RPM (formula given by Casey).

Yes torque is a measure of the twisting force being applied.

The best way I can explain it is with examples...

Take my snowmobile engine for example, 140hp/95ft-lbs tq from a 2 cyl 700cc 2 stroke.

The Saturn Ion has 140hp too but it's out of a 4 cyl w/ a lot more torque. For the sake of an example, if you tried to put that snowmobile engine in that saturn (all else being equal) thinking that since they both had 140hp that it would work ok....well...guess what....no...it wouldn't. The snowmobile engine doesn't have the tq necessary to push that car like the 4 cylinder would.

That snowmobile engine spins to 8000 rpm - the higher RPM and the marginal tq figure gives it that 140hp rating. If it didn't go to 8000 and went to say 5500 instead - it would have a much lower hp rating.


Hp really isn't what people make it out to be - its just that it's a widely accepted and known way to rate an engine's output. If you tell someone an engine has 200hp and then another has 500hp...they know that it's significantly more powerful.

Torque is a very important value but neither is more important than the other. They're both important.


Horsepower is just a measure of how quickly X amount of work can be done. Torque is that amount of work (w/ no time/speed value associated with it).

It is very complicated to get deeply involved with HP/TQ. Understanding what they are is 1 thing, but understanding how they relate to eachother through different applications and situations is another.

An engine with high horsepower and low torque....is an engine that gets a small amount of work done quickly. Where as a low hp engine with a lot of torque...will get a lot of work done slowly. Think of a small compact car engine vs a big rig diesel.

A Honda S2000 redlines at 9000 rpm and puts out 240hp but only 130ft-lbs. Compair that to a 400hp/1500ft-lb big rig diesel engine. That big rig diesel only goes to about 2800-3000 rpm so it has a low horsepower figure...the S2000 goes to 9000 rpm but only has 130ft-lbs...since it spins so fast it is rated at a higher HP figure.

It's just a relationship between tq and RPM.


Make sense?

On Edit:

I'll add this too...

It is possible to have two engines both producing 200hp - and one to be more powerful than the other. Horsepower numbers can be decieving. That saturn engine and my snowmobile engine both have 140hp - but that saturn engine is way more powerful overall.

 

Good explanation, Justin.

 

Thank you.

 

Post #2 on this thread was the best I have read on this topic.

https://www.ford-trucks.com/forums/s...d.php?t=481370

 

finally some explanations i can understand... spent the last hour looking through google trying to find a simple explanation between hp and tq to see which one was better to have but all them went over my head... shoulda searched FTE first... cuz this was way better than any others id read...

every stang forum ive been on people fight over how much HP they have to each other... and trucks its whos got more tq.. and never could understand why one was suppose to be better than the other that made them so different... granted i know tq is what pushes vehicles around.. but never understood how hp factored into them...

 

I'd like to add that the reason gasoline electric parallel hybrids work is due to the fact that electric motors produce maximum torque at stall, zero rpm. Mated with a modern gasoline engine that has the typical high rpm torque peak.

Diesel locomotives are series hybrids which use the tremendous torque of electric motors to move loads with a hp/weight ratio so low that you would not think it can work at all.

Jim

 

Actually you can have torque without horsepower. If you apply a twisting force to something and its not moving, torque is still being applied to it. Like when you are trying to break a rusty bolt free. They actually make special kinds of electric motors that are designed to be mechanically "stalled". They don't do any work, but they are still applying a force. 0HP while still having torque.

Also, a 200HP say diesel, is not more powerful then a 200HP high RPM gas job. Power is a measurement of force x distance (at least in mechanical terms) aka work. Both motors are capable of the same amount of work, but delivery it differently. If you gear that snowmobile motor correctly, it will move that saturn along just the same as that 140HP saturn motor would. The issue is that gearing it properly means getting the motor into its peak HP range, so that motor would be screaming its head off all the time, but both engines would still accelerate the car the same.

 

For the boy racers who talk trash about HP:

Horsepower sells engines.

Torque wins races.



-blaine

 

I'll guess you'll just have to tell all those F1 racing teams with 2.4L V8s making 700HP @ 19000 RPMs with only 200 lb-ft of torque that they are doing it wrong.

 

Yea, shift for your torque peak, see how that works in a drag race....

 

Have you seen how easily those cars stall out from a standing start, even with ultra-skilled $$$ professional drivers. I'll take torque over hp on the street. Our 50hp VW is easier to drive in traffic than the 200hp BMW was.

Jim

 

That wasn't the point? Fraken said that torque wins races, which is false. A torquey engine is easier and more pleasurable to drive, but HP is how much power the engine puts out. Power is what gives you top speed and acceleration, and actually determines how much you can ultimately pull at speed