Torque vs kW

[Debeer165]

Not likely.. If he had the 3.0 TDI then perhaps, but sadly the spread seems too wide for me. Especially considering the petrol / diesel situation

 

[Sinbad]

Not likely.. If he had the 3.0 TDI then perhaps, but sadly the spread seems too wide for me. Especially considering the petrol / diesel situation

And the FWD/RWD bit too...

 

[Colin62]

Nah, the small diesel doesn't stand a chance.

The thing with a Tdi is that because the power band is so wide, it pulls all the way through the revs fairly consistently and feels subjectively quicker than it actually is, cos it just keeps pushing, but when it's against the clock or against a powerful petrol, reality kicks in.

 

[Paul_S]

He keep arguing that he will ace me in a quarter mile because of the audi's torque. I am driving now with X5 19inch wheels which is heavy 16.5 kg without tyres. so i told him to wait till i replace my current wheels with the normal 17's the car came out then we can get a go to see who is the fastest. i am really curious to see if the audi can do it.

what do you guys think.

Torque means nothing if the engine isn't spinning fast enough to make enough kW.
The TDI doesn't have a chance unless you launch poorly or decide to drag race at 15000 feet above sea level.
Postmasburg is 4228 feet above sea level.

Sea level figures:
2012 Audi 2.0 TDI 0-100 km/h = 8.3 seconds
BMW E46 330i 0-100km/h = 6.5 seconds

 

[Rusty0]

Old but Interesting thread.

I have a 2001 Bmw E46 330i (170kw 300nm )and my friend a 2012 Audi 2.0 Tdi. that is (130kw 350nm).

He keep arguing that he will ace me in a quarter mile because of the audi's torque. I am driving now with X5 19inch wheels which is heavy 16.5 kg without tyres. so i told him to wait till i replace my current wheels with the normal 17's the car came out then we can get a go to see who is the fastest. i am really curious to see if the audi can do it.

what do you guys think.

Lol excuses...
If the TDi has software he will beat you...

I call TDi

 

[Pox]

Yeah a 3litre TDI might give you a run on a drag race, but not a 2litre. Torque and power are basically the same thing, how much energy the engine can deliver to the wheels.
The TDI will have more torque across the rev range, and torque is what makes you accelerate faster, gearing comes into play. The beemer can rev to 6000+ rpm, while the Audi is probably only around 4500. That means the audi gearing has to be a lot longer because of the shorter rev range. Longer gearing means slower acceleration.

 

[Paul_S]

Torque and power are basically the same thing, how much energy the engine can deliver to the wheels.

They are not the same thing.
Engine power (kW) is a function of torque at a given RPM.

Comparison:

Engine 1
Torque : 1000 Nm @ 0 to 1000 RPM
Max RPM : 1000 RPM
Max power at 1000 RPM = 104kW

Engine 2
Torque : 500 Nm @ 0 to 6000 RPM
Max RPM : 6000 RPM
Max power at 6000 RPM = 314kW

Which engine will drive a vehicle quicker given that the gearboxes are designed to match the engines?

I'll give you a hint:
The engine that revs lower will require a lower gearing to get the wheels to spin at a sufficient speed.
Lower gearing = less torque transmitted to the wheels.
Higher gearing = more torque transmitted to the wheels.

 

[Pox]

snip.

So basically what I said

Power is torque at a rev speed. The two are directly linked and are measured by how hard the engine can twist the drive shaft.

Similar power and torque - all down to gearing and weight. Diesels will always have longer gearing because of the lower rev range. Therefore they will have less acceleration for the same torque as a petrol.

 

[Drifter]

Killowatts sell cars, torque wins races.

 

[Drifter]

It's true for both normally aspirated and force induction engines.
The colder the air the more dense it is which means more air is induced and hence more fuel is added to the combustion process.
Hence the reason for inter-coolers on forced induction engines (although that is primarily to lower the air temperature which has been heated up due to the compression process).

Yesm but forced induction engines only lose about 5% at altitude vs the 17% of a N/A engine.

 

[Masataka]

Diesels are epic for that day-to-day driving as that low-down torque keeps the car alive without having to rev the hell out of it, but in the above situation, the 330i will kill the 2.0TDi as it's the power that makes the real difference.

 

[SauRoNZA]

An interesting question I've been pondering.

At present my wife drives 15km or so to work and back. This obviously means the fuel economy is sky high as the car never warms up properly to balance things out and I'm also thinking the Turbo probably isn't liking it very much (2.0T Petrol).

Now I'm wondering if we were to switch to a 1.9TDI for instance and maintain the same distances would the fuel economy be any better on a diesel with the short trips? Logic says they are better on average, but I have no personal experience on a short trip basis like this.

Also which one would be taking a harder knock with the short trips? Petrol or Diesel? Or does it amount to a paper value with no real world difference?

 

[Sinbad]

An interesting question I've been pondering.

At present my wife drives 15km or so to work and back. This obviously means the fuel economy is sky high as the car never warms up properly to balance things out and I'm also thinking the Turbo probably isn't liking it very much (2.0T Petrol).

Now I'm wondering if we were to switch to a 1.9TDI for instance and maintain the same distances would the fuel economy be any better on a diesel with the short trips? Logic says they are better on average, but I have no personal experience on a short trip basis like this.

Also which one would be taking a harder knock with the short trips? Petrol or Diesel? Or does it amount to a paper value with no real world difference?

wut?
My car is up to temp within 3km
Also, TDIs do warm up slower than petrol engines, but the economy will be much better. Guaranteed.

 

[Rusty0]

An interesting question I've been pondering.

At present my wife drives 15km or so to work and back. This obviously means the fuel economy is sky high as the car never warms up properly to balance things out and I'm also thinking the Turbo probably isn't liking it very much (2.0T Petrol).

Now I'm wondering if we were to switch to a 1.9TDI for instance and maintain the same distances would the fuel economy be any better on a diesel with the short trips? Logic says they are better on average, but I have no personal experience on a short trip basis like this.

Also which one would be taking a harder knock with the short trips? Petrol or Diesel? Or does it amount to a paper value with no real world difference?

15Km fuel saving per day, thats just being cheap

 

[Gaz{M}]

If we go back to basic physics then it makes sense:

An object that is accelerated needs to gain energy. Energy is measures in kw.

Given an infinitely long road, the engine with higher power will accelerate the car to the higher speed (if mass and drag are equal for both cars). This is only logical, because the engine with the lower energy output in kw can't possibly add more energy to the car than the engine that produces more kw.

Now to go a step further: speed results from the integral (or "sum) of all the energy added over time to a car.

The typical diesel engine has more torque than a petrol engine. But it can only add energy in small "bursts" in a rev range of 1500rpm to 4000 rpm and then a gear change is required, where no additional energy is delivered. Also, once a gear is changed, then diesel is at lower rpm and must build up revs to make more power (since power = revs x torque).

The petrol engine, on the other hand, can add energy over a much wider rpm band from 1000 to even 7000rpm. And when the gears are changed, then engine rpm drops to 4000 or 5000rpm maybe, which produces a lot more power than the diesel at 1500rpm.

These are just examples. But basically to sum it all up: The diesel adds energy in strong bursts or "lumps" to the car. The gives you that "thrust" in your back feeling. But the petrol car adds energy in a gradually increasing, consistent slope. This gives less of a push in the back feeling, but ultimately the amount of energy the petrol car adds to the car is higher when summed up.

This is why a car with more kw will ultimately win the race. It has to, all else being equal. But over shorted distances, the car with more torque might "feel" faster and win up to a point, until the energy needed to accelerate the diesel, cant beat the energy added to the petrol car.

 

[SauRoNZA]

wut?
My car is up to temp within 3km
Also, TDIs do warm up slower than petrol engines, but the economy will be much better. Guaranteed.

Yes the temp goes up but the losses in initial fuel economy from cold are massive. My 15km the GTI has barely settled below 15l/100. While if you do a longer trip of 30km for instance it will get to <10l/100km.

So at the moment the average on a tank is more like 11-12l/100 whereas before it was 8-10 l/100.

Do you think the Diesel will be better in the same conditions still?

15Km fuel saving per day, thats just being cheap

Huh?

 

[Quantum Theory]

Here is a real world example. Me and colleague. He kept boasting about power. I told him that torque and power band is more important.

118kW @ 5000-6200rpm and 250Nm @ 1500-4200rpm

vs

140kW @ 5900rpm and 230Nm @ 3500rpm


The 118kW is 0.2 seconds faster to 100km/h and above a 100km/h acceleration is also faster. Dual clutch vs standard auto obviously also helps.

 

[kripstoe]

Yes the temp goes up but the losses in initial fuel economy from cold are massive. My 15km the GTI has barely settled below 15l/100. While if you do a longer trip of 30km for instance it will get to <10l/100km.

So at the moment the average on a tank is more like 11-12l/100 whereas before it was 8-10 l/100.

Do you think the Diesel will be better in the same conditions still?

Huh?

Depends on driving style and traffic I suppose, but the diesel will still be better. Real world example. With my current client, I drive 16km to work, and 16km back to home. Durbanville to Bellville and back. At present I average 5l/100km in the 2.0 TDI. In the morning it's about 4.4-4.5. In the afternoons is about 5.5-5.6.

 

[SauRoNZA]

Depends on driving style and traffic I suppose, but the diesel will still be better. Real world example. With my current client, I drive 16km to work, and 16km back to home. Durbanville to Bellville and back. At present I average 5l/100km in the 2.0 TDI. In the morning it's about 4.4-4.5. In the afternoons is about 5.5-5.6.

Aaah okay. So it is still much better.

She drives half of the same roads oddly enough.

 

[Bmw.wp]

Lol excuses...
If the TDi has software he will beat you...

I call TDi

You will lol, you have my friends name.

what about the Gearbox and sport button option on the Audi (Auto).? Bmw are Manual.

i wonder if i must challenge him with the 19's wheels.? although i think i will be at a disadvantage then.lol.

and No both cars are standard, mine just decat.

Thanks guys.