Doonagoowin

Could somebody tell me what torque and horsepower is for?
Torque is for off the line speed and horsepower is for top speed right?

And what does RPM stand for?

DarkFire989

RPM- Rotations per minute

Not really sure about Torque and Horsepower though. Its a bit technical, I bet if you "search" for it on google or something you would get plenty of hits.

[link=http://en.wikipedia.org/wiki/Torque]Torque[/link]

[link=http://en.wikipedia.org/wiki/Horsepower]Horsepower[/link]

twomanytoys

Yes torque is what gets you moving while horse power keeps you moving.

sloppyG

hp=torque*rpm/5252

they're all related to each other

sheograth

Horsepower is a measure of power output, analogous to wattage. Torque is a measure of rotational force.

Force and power are fundamentally different.

SManMTB

Not really, power is torque per time unit.

GYNAIKAS

WO, WO, WO! Hold it! First of all rpm -> revolutions per minute (I think so ). Horsepower really does not "exist" as a basic measurement unit. Engine produces torque and only. That torque moves the crankshaft at some rpm range. Horsepower is torque*rpm.

Nitro Fumes

Both electric motors and steam engines put out torque at Zero RPM while combustion engines can't because at Zero RPM they aren't running (Duh for that one).

Access

Basically raw torque is concept of how hard you can 'push' at any point in the RPM band, with an ICE engine it typically builds up to a certain point and then starts to fall off. For things like towing, pushing, or running over difficult terrain, up hills, etc., it's important to have an engine that can provide enough torque at the lower end of the RPM band, aka 'low-end Torque'.

Horsepower is a measure of torque * RPM and ultimately more important for performance since any car has a transmission that is gearing things down to get a torque multiplier.

GYNAIKAS

Well in order to judge wich engine is better for a car you need to have the engine's specs and torque-rpm diagram ONLY. HP is a torque product at a certain rpm level. Torque is more important to me than the fancy HP numbers.

Access

Well ideally you want a torque curve that starts early and is usable over a wide range of RPM... as reasonably 'flat' as possible; but the HP thing means that torque @6000rpm is 'worth' twice that of torque @3000rpm since the former will lead to better torque on the wheels when you consider the gearing. That's all, raw HP numbers can be deceiving b'cos they only describe the engine's operation at the best particular point, and engines can be designed to maximize this particular number (at a single point) but still be horrible from an actual driving point of view they will take forever to actually get to that optimum point of operation and won't be able to stay there for very long.

sheograth

True, but thats how they are different and cannot be readily compared without the time element.

GYNAIKAS

That 3k and 6k example stands better for real cars wich use 5-7 different gearings. When running on track then the low end torque is what makes your car exiting the corners better. I'm not saying that you're wrong but I'm trying to say that it's really subjective. All depend on someone's needs.

Argess

Torque is a force. HP is Power. Two different things related by time (which means rpm). Specs usually tell you about one or both as "peak". Access has it right (above).....to determine performance, you need a graph over the rpm range. Peak numbers arn't very informative, regardless if they are torque or HP.

In fact, it is the need to overcome inertia that requires HP. Here's an example.....two identical vehicles. Absoletly the same, except for one thing: One has a light aluminum flywheel. The other a heavy steel flywheel. The vehicle with the aluminum flywheel will accelerate faster, BUT both cars will have the same top speed. In this case, peak HP (or brake HP) or peak torque readings won't show a difference, but a graph (as done with an inertial dyno) will.

So......all I can tell you, is that HP or torque graphs are great for modification testing (before and after graphs), but advertised numbers mean more or less......diddly squat for predicting performance.

Access

That's why I said "ideally you want a torque curve that starts early". If your low-end is very weak, you're going to be stuck there longer than you should be. It won't matter how much torque or power you can put out at 6000rpm if you never have a chance to get up that high (except on the longest of the long straights).

You see the 'numbers game' used in many different places, it isn't just cars. Look at something like digital cameras or computers or what-not where you have the ever-increasing megapixel count but the truth is the pictures they take look just the same or worse than they did 2 years ago.

GYNAIKAS

I totaly agree!!! [8D]

SAVAGEJIM

This is absolutely correct. Torque is the thing that acclerates a car. Torque is what keeps a car moving. Torque is what allows any car or truck to accelrate very fast and maintain a very high speed.

As for HP, you are correct here too. HP to us, the end user, is absolutely useless; it is only a bragging number. Worse, HP can be deceiving. It is very posible for a small block .12ci engine to produce the very same max HP as a .21ci big block. This is how it is commonly done:
The .12ci small block can rev will up to and even beyond 40000RPM, but throughout its entire RPM bandwidth, its torque output is small as compared to big blocks. The .12ci engine makes its HP from very high RPM, eve though its torque is miniscule.
The .21ci big block engine, being of a longer stroke (in most cases), would not be able to turn very high RPMs, but is torque is massive compare to te small block engine. So it does not have to turn much RPM to create the same HP as the small block. Its drawback is it cannotout-rev the small block
(NOTE: Even though there are many exceptions to this example I have given, there are many small block engines on the market today that can make more HP than many lower displacement big blocks.)

When comparing these two engines, even though the small block makes as HP as teh big block, take the small block out of the car taht it was in and put that big block in and the abssive torque will make it accelerate like a ocket. Also, to compnsate for big block's low RPM, bolt on a much much higher gear ration and that big block would be able to get that car to significantly faster top speed. The small block would not even have the torque to turn those gears.

2916jr

rpm=revolutions per minute

m_eller

if a evolution 80 has 40lbs. of torque how it compare to a da 85 with 9.0 hp[:@]

SAVAGEJIM

What? [sm=spinnyeyes.gif][sm=spinnyeyes.gif][sm=spinnyeyes.gif]

Do you mean that at 80 RPM a machine produces 40 ft-lbf? When it comes to torque, you MUST also have a length unit, only stating the force without the length unit is not torque. Other than that, I do not know what you mean

If you mean that 80 RPM a machine makes 40 ft-lbf torque, the machine is producing 0.61 HP!

The Mad Modder

Here's how it works. Torque+speed=horsepower

Dsyyke

rpm=revolutions per minute

SAVAGEJIM

LOL, this guy has not posted or even looked in this thread since like last summer! I am pretty sure he has found out what "RPM" means a long time ago!

warheadforever

Torque gets you going, Horsepower get you speed.

RPM, Revolutions Per Minute

camaross427

put it simply, if you want wheelies you want torque, if you want top speed you want more rpm, the best is having both