Question about Torque

[MQX87511]

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.

Before you get answer, you have to answer what is the significance of accelerate faster?

[Volvobrick]

I think many are still confused...

 

Torque and Power are directly related:

 

Power = Torque X RPM

 

The feel of the car is related to at what RPM the Torque or Power peaks.

 

Diesel engines have much higher torque at lower RPM but runs out of puff by about 4-4500 rpm, leading to lower HP. Petrol engines typically have lower peak torque but they rev much higher to 6-8000, thus leading to higher PEAK power. Of course turbo/supercharging will increase the torque across all rpm, for all engines.

 

In start-stop city traffic, when we have to accelerate from stop or very low speed, higher torque at lower rpm like diesels will have an advantage since the engine might not go beyond 3000 rpm before having to ease off the peddle. If the road is clear then a petrol engine (of similar capacity) will eventually catch up and overtake. A diesel taxi will out accelerate a WRX in the first 10-20 metres if both start from the normal engine idling speed.

 

If you don't rev your engine beyond 3-4000 (some don't rev beyond 2500!), then consider a car with higher torque at lower rpm even if the HP is lower (diesel is a perfect example), all other things being equal. You have to forgo any bragging rights of course!

[Silverkris]

I think in simple terms will be torque will greatly affect 0-100km/h timing. High Torque = Faster Timing provided the weight of the car is constant.

 

Power bhp will determine how much more faster your car can reach beyond 120km/h and stay there and beyond.

 

This is especially true for the modern cars who uses turbo chargers to achieve high torque using a smaller cc power engine.

 

I compared with my previous cars: Japanese 2.0NA (160bhp 180Nm) vs Continental 1.6 (123bhp 200Nm).

 

The continental definitely has better 0-100 timing but once it reaches highway speed, you will need careful planning before overtaking car in front as it runs out of power towards higher speed. The Japanese takes slightly longer time to reach highway speed but it can always overtakes with more ease.

 

That spoken, if you got a car with high power (above 200bhp) and torque (above 350Nm) you can do driving at ease, except having to brake unlimited time to avoid hitting the car in front.

[Nissan833]

3 cars for comparison,

 

Hyundai Sonata Taxi 2.0 CRDi (Turbo Diesel)

148 Bhp

Torque 305NM

0-100 @ 10.7sec.

Weight 1,660kg

 

Hyundai Santa Fe 2.4 GDI (NA Petrol)

189Bhp

Torque 242NM

0-100 @ 10.9sec.

Weight 1,694kg

 

BMW 520i 2.0 (Turbo Petrol)

181Bhp

Torque 270NM

0-100 @ 7.9sec.

Weight 1,725kg

 

Hmm.. very confused the heaviest is the fastest. The highest Bhp and power to weight has the lowest torque and is the slowest. The weakest Bhp and power to weight has the most torque and still slightly faster than the most powerful... So it's not the torque, not the Bhp and not power to weight??? Please enlighten me

 

Gearbox.

 

You compare Peugeot recent turbo petrol engines with VW ones of the same capacity and car segment, but VW usually will be faster by at least 1sec even though the BHP and torque figures are the same or with Peugeot slightly higher due to higher cc (1.5T Peugeot vs 1.4TSI VW).

[MQX87511]

 

Gearbox.

 

You compare Peugeot recent turbo petrol engines with VW ones of the same capacity and car segment, but VW usually will be faster by at least 1sec even though the BHP and torque figures are the same or with Peugeot slightly higher due to higher cc (1.5T Peugeot vs 1.4TSI VW).

agree, in same condition,

DCT/DSG > MT >CVT >AT

[chuanyan128]

acceleration speed is a combination of so many factors, not so straight forward.

 

but the most important are :

 

1. weight

2. horse power

2. torque

4. powerband

5. gear ratios (to match the above)

6. traction

7. aerodynamics (at higher speed)

 

Also driver and mistress weight

[Koko]

From this topic... can find out that many are not studying mechanical engineering...

 

 

[Piyopico]

From this topic... can find out that many are not studying mechanical engineering...

 

 

My fren. The money is in business, finance and banking.........

 

😁

[Mr_b20]

 

Gearbox.

 

You compare Peugeot recent turbo petrol engines with VW ones of the same capacity and car segment, but VW usually will be faster by at least 1sec even though the BHP and torque figures are the same or with Peugeot slightly higher due to higher cc (1.5T Peugeot vs 1.4TSI VW).

 

faster piang also