Torque?

Opsimath

Senior Member
Joined
Apr 20, 2015
Messages
4,525
Reaction score
4,057
Location
North Florida
The Dream Cars thread discussions were over my head enough to send me searching for an understanding of torque. I'm still kinda confused. Can you see all those question marks over my head????

Per my reading, torque is power that gets you going from a standstill and horsepower is power to keep going and reach top speed.

Unfortunately I want to understand torque and how it's figured, maybe even how it's produced. The need to understand is a curse, by the way!

So from my reading, a foot-pound of torque is the amount of power measured in a linear foot from a pivot point. Huh? What's the pivot point in an engine? What linear foot is being measured?

I apologize for the questions, but as engine mechanics are most often a guy thing I thought perhaps some of my friends here might have an explanation that could help me understand, and relieve a small part of the curse!

Thank you!
 

SFIV1967

Venerated Member
Joined
Nov 20, 2010
Messages
18,442
Reaction score
8,956
Location
Bavaria / Germany
Guild Total
8
I don't know if this would help?



Ralf
 

gjmalcyon

Senior Member
Gold Supporting
Joined
Feb 6, 2011
Messages
4,179
Reaction score
2,417
Location
Gloucester County, NJ
Guild Total
13
Here's what OpenAI's CHATGPT4 says:

Torque and horsepower are both important measurements of an automobile engine's performance, but they represent different aspects of the engine's power output.

Torque is a measure of the twisting force that an engine can generate, usually measured in pound-feet or newton-meters. It is a measure of the engine's ability to turn the wheels, and it is what determines an engine's acceleration and towing capability. In simpler terms, torque is the force that gets a car moving from a standstill.

Horsepower, on the other hand, is a measure of the engine's power output, usually measured in horsepower or kilowatts. It is a measure of how much work an engine can do over time. Horsepower takes into account both the engine's torque and its rotational speed, so it reflects how fast the engine can produce the torque. In simpler terms, horsepower is what keeps a car moving at high speeds, once it's already in motion.

In summary, torque is the force that gets a car moving, while horsepower is what keeps it moving at high speeds. A car with high torque will have good acceleration and towing capability, while a car with high horsepower will have a higher top speed.
 

Default

Super Moderator
Platinum Supporting
Joined
Jul 30, 2007
Messages
13,595
Reaction score
3,008
Location
Philly, or thereabouts
Guild Total
11
Torque is roughly equivalent to how much you can lift, horsepower is how fast you can run.
The function of the transmission is to transfer torque and horsepower efficiently as possible to the wheels, according to the application.

My Subaru Forester has a six speed transmission because the engine has horsepower but not torque. Think of each gear as a ramp, which makes it easier for the weak engine to push the weight of the car to a certain engine rpm. Once that rpm is reached, and the engine can't push any harder, you switch into the next gear, which is the bottom of another ramp. Now it's easier for the engine to push the Forester to a higher speed. You go through each gear until you earn a "95 mile an hour in a school zone" certificate.

As an example of torque, pick any electric vehicle. They have generally a one speed transmission because they have so much torque that they don't need any "ramps" to push those heavy batteries up to speed.

Why don't ev's have geared transmissions? They don't need them, unlike internal combustion engines.
 

Opsimath

Senior Member
Joined
Apr 20, 2015
Messages
4,525
Reaction score
4,057
Location
North Florida
If electric vehicles have high torque would they pull a loaded 3-horse trailer as well as or better than a gas or deisel engine?
 

gjmalcyon

Senior Member
Gold Supporting
Joined
Feb 6, 2011
Messages
4,179
Reaction score
2,417
Location
Gloucester County, NJ
Guild Total
13
If electric vehicles have high torque would they pull a loaded 3-horse trailer as well as or better than a gas or deisel engine?

Thanks to the high torque, an electric vehicle towing a horse trailer might accelerate faster or climb hills better than an ICE (internal combustion engine) tow vehicle. However, my understanding is towing with an electric vehicle dramatically reduces rated range since the electric motor(s) are working harder and pulling more current.
 

Default

Super Moderator
Platinum Supporting
Joined
Jul 30, 2007
Messages
13,595
Reaction score
3,008
Location
Philly, or thereabouts
Guild Total
11
That is the downside of an ev. Around, my dad had a Chevy dual wheel pickup that he used for pulling a travel trailer, and that got horrid gas mileage even when he wasn't pulling a trailer. Everything has trade-offs.
 

Nuuska

Enlightened Member
Joined
Jan 18, 2016
Messages
7,668
Reaction score
6,028
Location
Finland
Guild Total
9
You might also think it this way - electric car towing heavy load consumes near or same as ICE - under lighter conditions EV consumes only fraction of energy of ICE. - NOT FORGETTING the initial buying prize - which is higher on EV.

Depending where you are - climate - energy prize ( gas vs electricity ) - and what your driving needs are - should give you the answer of the economy EV vs ICE.

Over here we need heating about 8 months - 3 months cold - 5 months cool or mild - ICE delivers that automatically - though slowly - EV gives heat immediately at cost of reduced range. Electricity is cheap vs gasoline here. Charging at home when you live in a house is no-brainer. For those living in condos it gets a bit complicated and more epensive.

Torque and acceleration is fantastic - in city traffic w 30mph speed limit I can easily leave any BMW behind me in traffic light start - if I wish to do so. Usually I don't bother . . . But my little SEAT eMii is very zippy.

And consumption
- summer in the city about 7kWh/100km = quart of gasolin for 62 miles = 248mpg - my actual figures based on my driving style.
- winter and higway no more than that triple = 80mpg

You notice that the consumption is kind of inverse of ICE-car - less in city traffic - more on highway.
 

adorshki

Reverential Member
Joined
Aug 21, 2009
Messages
34,176
Reaction score
6,790
Location
Sillycon Valley CA
Here's what OpenAI's CHATGPT4 says:
Horsepower takes into account both the engine's torque and its rotational speed, so it reflects how fast the engine can produce the torque. In simpler terms, horsepower is what keeps a car moving at high speeds, once it's already in motion.

It's not how fast the engine CAN produce torque, it's how quickly the engine IS producing torque. Torque is the force required to induce movement of an object at rest. Horsepower is how quickly that torque is being applied.

In general, as rpms go up, both torque and horsepower increase until they reach the top of their respective output curves.
As the horsepower goes up with rpms, it produces the corresponding rpm torque more quickly as the rpms increase.
A car with high torque will have good acceleration and towing capability, while a car with high horsepower will have a higher top speed.
A lousy, even incorrect, generalization. Acceleration is a function of horsepower and gearing, NOT torque. And high horsepower doesn't guarantee "higher top speed", that's a function of the final gear ratio and aerodynamics with any given engine and bodywork, nothing else. All you get is quicker acceleration.

Take the case of diesel engines: The reason they're the default engine for heavy hauling is that they develop very high torque at very low rpms.

You don't normally want to get a 10-20,000 lb trailer moving with a quick jerk off the line, you want a steady gradual no-wheelspin controllable pull. Nobody drag races diesels, they have tractor pulls. Although Audi won the 24 hours of LeMans with a turbo-diesel few years back, the cars were geared especially for racing and in fact it was the fuel economy allowing fewer pit stops that edged out the win in the end, not simply a "faster car".

You notice that the consumption is kind of inverse of ICE-car - less in city traffic - more on highway.
This is where inertia comes in: The Newtonian rule of physics that an object in motion tends to stay in motion until acted on by an outside force. That's why ICE's are more efficient at freeway cruising speeds.

Electric motors produce 100% of their torque across their entire rpm range. Since there are no transmissions, vehicle speed is a direct 1-1 correlation to motor rpm.

So when that motor is turning higher rpms to deliver higher speeds, it's using as much electricity as required to get that rpm. One can't 'coast" with an electric car. If one lifts off the throttle, regenerative braking kicks in, and all the energy used getting to speed is immediately turned to battery-stored energy and wasted heat, but the energy recovered from braking can never equal or exceed the energy used to attain a given speed in the first place.

In a gas vehicle, once I get to the desired speed, inertia keeps the car moving and far less energy input from the engine is needed to maintain a steady speed. Using the transmission, a higher gear may then be selected which allows the engine to turn more slowly and use less gas, while still producing "just enough" power to maintain speed.

With an electric motor it's all or nothing and how fast do you want it? You're gonna use more power to go and keep going faster because it's generating 100% output all the time no matter what the rpms are.
In a sense, electric motors could be said to be "digital" in that they're either on or off, and ICE's are good old analog where everything happens on the continuum of a curve.

Maybe this is a better analogy:
One can't simulate a dimmer switch by trying to flip a 100-watt bulb on and off rapidly. It's always at 100% when it's on.

A dimmer switch allows voltage reduction so there's less lumens output, continuously.
 
Last edited:

NM156

Member
Joined
Aug 21, 2022
Messages
112
Reaction score
132
Guild Total
1
A while ago, I did more reading than I care to on horse trailer towing. Almost bought a '87-'91 body Ford 250 diesel with the 6.9L International school bus engine. It has so much torque that towing anything is no problem. However, most of those trucks look like lawn trophies now.

Newer diesels have more parts that can break, and are horrifically expensive. Used ones are still outrageously expensive and often have rust issues. As @gjmalcyon said, electric trucks have disappointingly low range when working hard, at least that's what I read.

In the end, my research led me to the Tundra with the 5.7L engine. Only the current year has trailer backing assist. These are also hybrids, I think, with good gas mileage. They are more than twice as much as I was willing to spend.
 

Nuuska

Enlightened Member
Joined
Jan 18, 2016
Messages
7,668
Reaction score
6,028
Location
Finland
Guild Total
9
. . .

Maybe this is a better analogy:
One can't simulate a dimmer switch by trying to flip a 100-watt bulb on and off rapidly. It's always at 100" when it's on.

A dimmer switch allows voltage reduction so there's less lumens output, continuously.

Actually the dimmer works in a manner that it delays the ON-switching after each half-wave - therefore it is a pulse-ratio-regulator on sinewave. So the bulb is always 100% ON for the few milliseconds that the power is available.

A transformer dimmer like VARIAC then lowers the voltage - resulting in lower power w constant sinewave.


1679182040786.png
 

adorshki

Reverential Member
Joined
Aug 21, 2009
Messages
34,176
Reaction score
6,790
Location
Sillycon Valley CA
Actually the dimmer works in a manner that it delays the ON-switching after each half-wave - therefore it is a pulse-ratio-regulator on sinewave. So the bulb is always 100% ON for the few milliseconds that the power is available.

A transformer dimmer like VARIAC then lowers the voltage - resulting in lower power w constant sinewave.


1679182040786.png
I stand humbly corrected for the inaccurate analogy, but the principle still applies, no?
 

davismanLV

Venerated Member
Joined
Mar 24, 2011
Messages
19,196
Reaction score
11,812
Location
U.S.A. : Nevada : Las Vegas
Guild Total
2
So my take... to make it simple is HP will move your car forward. Torque will flip it over... and that's where the hideous crap happens.... it's a balance. I get stupid when these convos happen!!
 

adorshki

Reverential Member
Joined
Aug 21, 2009
Messages
34,176
Reaction score
6,790
Location
Sillycon Valley CA
So my take... to make it simple is HP will move your car forward. Torque will flip it over... and that's where the hideous crap happens.... it's a balance. I get stupid when these convos happen!!
Torque is technically defined as "twisting force".

Let's take the classic case of the lever:
Lever-Simple-Machine.jpg

In this case the rotation occurs at the fulcrum as shown by the arrows. "Effort" represents the amount of torque required to move the load at the length of the lever from the fulcrum to the end at which "effort" is applied. You may recall the very simple principle that the longer the lever on the "effort" side of the fulcrum, the less "effort" is required to lift the load. (And why torque is measured in "foot pounds") That's essentially what transmissions do, change the length of the lever, on a cog rather than a straight line. They multiply torque.

Torque multiplication: The bigger the size difference between the transmission gear cog and the gear in the rear end differential, the more torque is generated. So first gear lets you get started using reasonable rpms but tops out at a low top speed when the engine hits its rpm limit. As progressively higher (larger diameter) gears are selected in the transmission, engine rpms remain in a useful and/or efficient range while inertia helps the vehicle remain in motion.

Now, how fast can you lift that load? At any given lever length you can push faster (analogous to rpms increasing in an ICE vehicle). That's horsepower.

Or you can make the lever longer and for the same arc of travel on the your end you get a proportionally larger arc of total lift for the load, which translates to quicker lift.

That's how gearing and torque multiplication generate acceleration force from a given amount of torque and rpm, which is what horsepower really is.
 
Last edited:

davismanLV

Venerated Member
Joined
Mar 24, 2011
Messages
19,196
Reaction score
11,812
Location
U.S.A. : Nevada : Las Vegas
Guild Total
2
Torque is technically defined as "twisting force".

Let's take the classic case of the lever:
Lever-Simple-Machine.jpg

In this case the rotation occurs at the fulcrum as shown by the arrows. "Effort" represents the amount of torque required to move the load at the length of the lever from the fulcrum to the end at which "effort" is applied. You may recall the very simple principle that the longer the lever on the "effort" side of the fulcrum, the less "effort" is required to ft the load. That's essentially what transmissions do, change the length of the lever, on a cog rather than a straight line. They multiply torque.

Torque multiplication: The bigger the size difference between the transmission gear cog and the gear in the rear end differential, the more torque is generated. So first gear lets you get started using reasonable rpms but tops out at a low top speed when the engine hits its rpm limit. As progressively higher (larger) gears are selected, engine rpms remain in a useful and/or efficient range while inertia helps the vehicle remain in motion.

Now, how fast can you lift that load? At any given lever length you can push faster (analogous to rpms increasing in an ICE vehicle). That's horsepower.

Or you can make the lever longer and for the same arc of travel on the your end you get a proportionally larger arc of total lift for the load, which translates to quicker lift.

That's how gearing and torque multiplication generate acceleration force from a given amount of torque and rpm, which is what horsepower really is.
Wait... isn't that what I said? Do we need to get Hans in here now/??/ Jeeze....
 
Top