Question about Torque

[mogoloop]

Assume 2 different cars with same 200nm of torque. One car weighs twice as much as the other. Does this mean the lighter car will accelerate faster than the heavier?

Just wondering how to compare the torque figures in the sales brochures.

[Chowyunfatt]

[Toothiewabbit]

Fatt gor has spoken.

 

 

 

[Watwheels]

  On 5/15/2015 at 3:57 AM, mogoloop said:

Assume 2 different cars with same 200nm of torque. One car weighs twice as much as the other. Does this mean the lighter car will accelerate faster than the heavier?

Just wondering how to compare the torque figures in the sales brochures.

 

You look at the two cars at what rpm does the max torque come on?

 

If let's say one car's engine is NA and the other is TC...

 

TC say 200Nm at below 2K rpm vs NA 200Nm at 4200rpm, let's say weight is constant and gearbox is the same. The car with the TC engine will accelerate faster.

 

Better to test drive to see how the 2 cars respond to your right foot. That the brochure won't be able to tell that or tell you the difference. How the throttle respond, what kinda gearbox is used, how it's programmed to perform, a number of factors that will affect the acceleration. Numbers only tell you one thing. Test drive tells you more.

[Porker]

  On 5/15/2015 at 3:57 AM, mogoloop said:

Assume 2 different cars with same 200nm of torque. One car weighs twice as much as the other. Does this mean the lighter car will accelerate faster than the heavier?

Just wondering how to compare the torque figures in the sales brochures.

Generally true. The Porsche 993 GT2 accelerates the fastest.

 

😂

[Opel17]

  On 5/15/2015 at 3:57 AM, mogoloop said:

Assume 2 different cars with same 200nm of torque. One car weighs twice as much as the other. Does this mean the lighter car will accelerate faster than the heavier?

Just wondering how to compare the torque figures in the sales brochures.

Yes, in this case lighter car will accelerate faster.

* experiment : carry 1 bag of rice and run vs 2 bags of rice and run.

 

Sales brochures usually will indicate the 0-100 kmh timing for customer to compare.

[Myxilplix]

Basic physics question, no?

 

More torks with less weight for the win.

[Nzy]

  On 5/15/2015 at 4:25 AM, Watwheels said:

 

You look at the two cars at what rpm does the max torque come on?

 

If let's say one car's engine is NA and the other is TC...

 

TC say 200Nm at below 2K rpm vs NA 200Nm at 4200rpm, let's say weight is constant and gearbox is the same. The car with the TC engine will accelerate faster.

 

Better to test drive to see how the 2 cars respond to your right foot. That the brochure won't be able to tell that or tell you the difference. How the throttle respond, what kinda gearbox is used, how it's programmed to perform, a number of factors that will affect the acceleration. Numbers only tell you one thing. Test drive tells you more.

 

In TS's case though, I think it should be the lighter car that is faster. Cuz the heavier car is twice as heavy. Sure can't outrun a car with same amount of power and half the weight.

 

Its like comparing the weight of QQ to a S-class. But both with same torque. Even if the lighter car's torque comes in at 4000rpm and the heavier car's at below 2k, I don't think the heavier car can win.

Edited May 15, 2015 by Nzy

[Count-Bracula]

  On 5/15/2015 at 4:02 AM, Chowyunfatt said:

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Funny meh? torque torque torque . . CHENG!

[Watwheels]

  On 5/15/2015 at 4:33 AM, Nzy said:

 

In TS's case though, I think it should be the lighter car that is faster. Cuz the heavier car is twice as heavy. Sure can't outrun a car with same amount of power and half the weight.

 

That of course is a no brainer question.

I'm thinking in practical sense. Coz at 200Nm of torque there's no car that's 2 times as heavy as the other. Unless it's loaded with passengers and barang barang. That wouldn't be a fair comparison anyway. Numbers do not usually tell you the whole story. Anyway when you give a scenario some factors must be consistent but dan cars are made differently from different car makers. The only way to tell or rather the best way to tell is to test drive the cars.

Edited May 15, 2015 by Watwheels

[Lowrider]

Simply put, car with lower RPM to reach the same torque would accelerate faster.

[Enye]

  On 5/15/2015 at 3:57 AM, mogoloop said:

Assume 2 different cars with same 200nm of torque. One car weighs twice as much as the other. Does this mean the lighter car will accelerate faster than the heavier?

Just wondering how to compare the torque figures in the sales brochures.

 

yes provided the torque curves are similar

 

power to weight is a better measure

Edited May 15, 2015 by Enye

[mogoloop]

  On 5/15/2015 at 9:16 AM, Enye said:

 

yes provided the torque curves are similar

 

power to weight is a better measure

Thank you.

[Zyklon]

Many people confused by diesel torque and what not...all from marketing bulls**t or confused individuals spreading the wrong idea...or was it topgear that said something along of the fastest you can reach and how fast you can reach the fastest.

 

You CANNOT use torque as the sole indicator of acceleration. You need to use power which is the function of torque and rpm. This means that assuming both cars are at full throttle and both are equally aerodynamic...

 

Car A: 200Nm torque, weighs 1000kg, engine running at 2000rpm

Car B: 200Nm torque, weighs 2000kg, engine running at 4000rpm

 

Layman will tell you that Car A is faster. Of course ma, at 2000rpm already 200Nm torque. Some more car A is lighter leh. WRONG.

 

Actually both car A and car B will have same acceleration at this moment.

 

In the similar manner, if Car A is a diesel hatch making 200Nm from 1500-4000rpm and weighs 1000kg. Car B is a 2000kg limo with a high reving petrol engine, making 200Nm from 3000-8000rpm. Both will actually be equally fast in acceleration if drag and drivetrain lost are the same. The difference is in their power and top speed will definitely differ.

 

Don't believe me? Draw out the free-body diagram and write their equation of motion.

Edited May 15, 2015 by Zyklon

[Jjchsg]

The easiest way is to look at power to weight ratio. Yes, power, not torque. Power to weight is a primary deciding factor assuming that there is no significant difference on the gearbox. Have you ever hear people quoting torque to weight ratio?

[Xers007]

  On 5/15/2015 at 2:28 PM, Zyklon said:

Many people confused by diesel torque and what not...all from marketing bulls**t or confused individuals spreading the wrong idea...or was it topgear that said something along of the fastest you can reach and how fast you can reach the fastest.

 

You CANNOT use torque as the sole indicator of acceleration. You need to use power which is the function of torque and rpm. This means that assuming both cars are at full throttle and both are equally aerodynamic...

 

Car A: 200Nm torque, weighs 1000kg, engine running at 2000rpm

Car B: 200Nm torque, weighs 2000kg, engine running at 4000rpm

 

Layman will tell you that Car A is faster. Of course ma, at 2000rpm already 200Nm torque. Some more car A is lighter leh. WRONG.

 

Actually both car A and car B will have same acceleration at this moment.

 

In the similar manner, if Car A is a diesel hatch making 200Nm from 1500-4000rpm and weighs 1000kg. Car B is a 2000kg limo with a high reving petrol engine, making 200Nm from 3000-8000rpm. Both will actually be equally fast in acceleration if drag and drivetrain lost are the same. The difference is in their power and top speed will definitely differ.

 

Don't believe me? Draw out the free-body diagram and write their equation of motion.

 

i am not a physics guy ... may i ask so what is the power to weight ratio for??

 

[Ezfaun]

A very simple analogy is that torque is what catapults you forward from a stop and hp is what pulls you further and further away.

Torque is good for immediate response down low while hp is good for revability higher up the range.

 

Different driver will have different preference so always test with your heart before you decide.

[Zyklon]

  On 5/15/2015 at 4:12 PM, Xers007 said:

 

i am not a physics guy ... may i ask so what is the power to weight ratio for??

 

Power to weight ratio only tells you the acceleration.

 

In my example...both cars have the same power to weight ratio.

 

What power to weight does not tell you is the higher speed acceleration and top speed. Same power to weight, but higher total power will usually be way faster once you reach 200+km/hr.

 

In layman terms:

 

Power to weight is the same as

Pushing energy per unit mass per unit time, which is the same as

Pushing force per unit distance per unit mass per unit time

 

Therefore higher power to weight means 1kg of mass will have more pushing force.