Educate me about torque...

Messages
1,203
Location
Oregon
quote:
but how do I determine the overall "torque curve?"
acewiza is right, a dyno is the only acceptable way to measure torque curve. Unless you can find some copys of OEM dyno sheets or charts and graphs from dyno testing you are out of luck.
 
Messages
6,902
Location
Louisiana
There's a formula tied to hp, IIRC. Torque is your friend and a car with a lot of torque down low is great for stoplight smiles. My big family car Saab 9-5 only makes 185 hp but it makes 211 ft lbs of torque just over 2k rpms so it feels MUCH faster.
 
Messages
4,378
Location
Camas, WA
Due to the way that hp and torque is commonly reported, peak, I find torque to be a more useful measure for vehicles that need to move things, and hp for vehicles that need to accelerate quickly. 300 peak hp could describe a drag bike, a hot 3L gas engine, a decent 6L gas engine, or an 11 liter diesel. Torque among those vehicles could vary from 150 to 2000 lbs/ft. The high torque allows more hp at low rpm, which is nice for getting say an 80k lb load moving, but such engines don't have say 10k rpm peaks like a larger bike which can produce lots of hp at higher rpms. A lower torque / higher hp engine can be pressed into service for moving loads, a friend has a 20k lb flatbed that uses a Chevy 350, but it's geared to max out at about 55mph, you need to use the throttle like a light switch, and the truck is on it's second engine with something like 80k miles on it.
 
Messages
57
Location
Melbourne, FL
Basics: Torque is a twisting force. A force is a vetor quantity: it has a quantity and a direction. To accelerate a mass a force is required (F=MA). Horsepower is a scalar quantity and is the ability to do work. In an automotive context torque (at the drive wheel(s) determines acceleration and horsepower (the work done to move a vehicle through a fluid (air)) and determines top speed. The equation to calculate horsepower from torque is: HP = (torque * RPM)/5252 A reasonable piece on how this all applies to cars is here: http://vettenet.org/torquehp.html
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by The Critic: Besides that. [Big Grin]
Google the engine model and dyno, then select the images option in google. If your engne has much interest to the performance types, there are probably several dyno charts on google. If the doesn't work, try your car model and dyno.
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by Brett Miller: Torque is actually what does the work when getting a car moving. It's simply a measure of resistance.
Torque is a force. Horsepower is work.
 
Messages
267
Location
Idaho
quote:
Originally posted by XS650:
quote:
Originally posted by Brett Miller: Torque is actually what does the work when getting a car moving. It's simply a measure of resistance.
Torque is a force. Horsepower is work.

Yup. Some steam engines and certain electric motors can exert torque at zero rpm. Since nothing moves, no work is accomplished, therefore no horsepower is developed, even though force is being applied. Think about pushing on a wall as hard as you can without moving the wall. You will get tired, but no work is done. Horsepower is moving a given load some distance in a measured amount of time. 550 lbs/ft of work per second = one hp. Joe
 
Messages
57
Location
Melbourne, FL
quote:
Originally posted by Lazy JW: Yup. Some steam engines and certain electric motors can exert torque at zero rpm.
An electric motor develops its maximum torque at stall (0 rpm).
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by b_rubenstein:
quote:
Originally posted by Lazy JW: Yup. Some steam engines and certain electric motors can exert torque at zero rpm.
An electric motor develops its maximum torque at stall (0 rpm).

Some do, some don't.
 
Messages
1,080
Location
Illinois
quote:
Originally posted by The Critic: I often see automakers publish an engine's maximum torque at a specific RPM (i.e. [email protected] 3750RPM), but how do I determine the overall "torque curve?" TIA.
If you also have maximum hp at a specific RPM you can use the relationship HP = (torque * RPM)/5252 to get another point on the curve. Rearrange it to: Torque = 5252 * HP / RPM A gross approximation of the curve is a straight line between the two points.
 
Messages
39,805
Location
Pottstown, PA
Come clean, Critic. You're trying to construct an agrument that you need to lace with apparently cogent statements. You wish to include "torque curve" in that presentation ..but don't have a grip on it yet. So what's the real motivation here [Confused] Don't worry. Your cover won't get blown on whatever alternate board this is going on. [Big Grin]
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by BrianWC: There's a formula tied to hp, IIRC. Torque is your friend and a car with a lot of torque down low is great for stoplight smiles. My big family car Saab 9-5 only makes 185 hp but it makes 211 ft lbs of torque just over 2k rpms so it feels MUCH faster.
Yep. Wife's Aerostar 3.0 is 145 hp and 165 pound-feet of torque maximums. My '95 F`150 is also 145 hp, but 265 pound feet of torque. I doubt there is much difference in their stoplight performance, but the higher torque F150 sure feels faster and is a lot more fun to drive.
 
Top