No, I think you still have a fundamental misunderstanding, or perhaps we are talking at crossed purposes.

as I understand it you seem to be suggesting that torque is related to speed. Whist in a motor the torque does change with rotational speed this is not due to the speed per se but the efficiency with which the input energy is being utilised which varies with a large number of variables ONE of which is rotational speed. otherwise how can the example I gave, the RS4 V8, provide 300nm at 1200rpm, 430nm at 6000 rpm and 320 at 8000rpm yet the power increases almost linearly from 1200 to 8250 rpm?

To say the engine torque doesn't drive the wheels may be semantically possible to believe, but effectively the engine torque drives the gearbox input shaft which drives the final drive which turns the wheels through the drive shafts. Without engine torque there is no torque at the wheels nor power.

There can be a state where the engine is turning but no torque is transmitted to the wheels e.g when the clutch is depressed. The power being generated by the engine is being utilised merely to keep the engine turning and drive ancilliaries such as oil and water pumps, alternator etc. this requires torque at the crankshaft or it would not turn.

Power is rate at which work is done. Something has to be changing for power to exist.

Torque is turning force. Something does not have to be changing to be generate torque. A steam engine provides maximum torque when stationary.

As your equation shows, Power in a motor is the product of the torque times the angular velocity. So there can be no power without torque in a rotating engine. So it would be more accurate to say power is the result of the torque rather than torque is the result of power as you seem to be suggesting

Edited 2 October, 201510 yr by Bristolf2b

Credit Suisse estimates this will cost VW $23Bn to $87Bn in fines, compensation and lost sales, and that the fallout may last a decade. So far BP have spent £50Bn paying for the Gulf of Mexico spill. The VW mess could end up being of equal or larger size in terms of final costs.

 

Then again, what do Financial Services Experts know?

No, I think you still have a fundamental misunderstanding, or perhaps we are talking at crossed purposes.

as I understand it you seem to be suggesting that torque is related to speed. Whist in a motor the torque does change with rotational speed this is not due to the speed per se but the efficiency with which the input energy is being utilised which varies with a large number of variables ONE of which is rotational speed. otherwise how can the example I gave, the RS4 V8, provide 300nm at 1200rpm, 430nm at 6000 rpm and 320 at 8000rpm yet the power increases almost linearly from 1200 to 8250 rpm?

To say the engine torque doesn't drive the wheels may be semantically possible to believe, but effectively the engine torque drives the gearbox input shaft which drives the final drive which turns the wheels through the drive shafts. Without engine torque there is no torque at the wheels nor power.

There can be a state where the engine is turning but no torque is transmitted to the wheels e.g when the clutch is depressed. The power being generated by the engine is being utilised merely to keep the engine turning and drive ancilliaries such as oil and water pumps, alternator etc. this requires torque at the crankshaft or it would not turn.

Power is rate at which work is done. Something has to be changing for power to exist.

Torque is turning force. Something does not have to be changing to be generate torque. A steam engine provides maximum torque when stationary.

As your equation shows, Power in a motor is the product of the torque times the angular velocity. So there can be no power without torque in a rotating engine. So it would be more accurate to say power is the result of the torque rather than torque is the result of power as you seem to be suggesting

 

I agree I have taken some shortcuts. But this is all about physics.

The transmission is multiplying the engine torque in such way the maximum torque available at wheels is far higher than the one generated by the engine.

As an exemple, with the 1.4 TSI (250Nm), you have a max torque at wheels between 1900Nm and 500Nm in a speed range from 50 to 200km/h.

 

On the other hand, the energy is kept the same, as learnt from thermodynamics laws.

We estimate the transmission brings 85% of the power to the wheels as a standard value. The remaining is lost in friction and heat.

 

This is not that the torque at wheels is really depending on the speed.

This is that assuming you bring (85% of) the max power to the wheels, in order to benefit the highest possible force and then reach the max acceleration, then you have the relation between Power and torque at the wheel as I mentioned before: Torque (at wheel) = R . Power / Speed.

 

As such, the max acceleration of the car is only depending of the achievable power, and has nothing to do with the engine torque.

Having studied in details the gearbox and axle ratio of all Octavias, I can tell it is built so that whatever the speed you are, you always have a gearbox ratio available to allow the engine to provide its max power. 

 

As a consequence, the max acceleration is depending on the max power, air penetration, friction and weight.

As I said, the engine torque as no influence on the performances.

 

As a practical exemple, while having very different values for max torque (250 vs 380Nm), but similar max power (180 vs 184hp), the 1.8 TSI and the RS TDI O3 have very close performances.

The petrol with its lower torque, has even beter results in 80 to 120 km/h acceleration. 

 

I know this is not aligned with what is supposed to be common knowledge. But you'd better ask engineers rather than journalists on such topics.

What is the differenc in weight between the two?

But if the torque and power characteristics are matched to the transmission ratios as is clearly the case, it is the available torque x angular speed at the crankshaft that allows, via the drivetrain , what you call "achievable" power at the wheels. If you have less torque as measured at the crankshaft, as transmission losses are pretty universal, with 'optimal gearing' then you will have less torque at the wheel to provide the 'achievable power' acceleration.

Another real world example:

My partner had a 1.6 Normally aspirated petrol Polo. It's rated power was 105 ps 148nm torque at 4500 rpm and a kerb weight of 1056kg. Max hp at 5000rpm

0-62 10.6 sec

She replaced it with a 1.2 Tsi. Rated power 105ps, 175 nm torque at 1550 rpm kerb weight 1126kg

0-62 9.7 sec max hp also 5000rpm

Since they had a very similar weight, an almost identical shape, the same tyre dimensions etc. and the same rated power output what was the difference?

In terms of 'driveability' there was an even greater difference than the figures would suggest, as the 'achievable power' was available much lower in the rev range. In gear acceleration is greatly improved, rather than just the artificial 0-60 time.

Most people do not exceed 3000 rpm in gears during general driving so the LPT provides more torque at lower revs when the 'achievable power' is most needed.

Edited 2 October, 201510 yr by Bristolf2b

For the comparison, this is not surprising. On top of having more torque, a petrol engine essentially gets its max power far earlier in revs than  atmoshperic petrol, and for a longer range.

Meaning it will get power sooner and longer during a 0 to 100km/h exercise.Theoritically, the difference would not be so visible on a 80 to 120 km/h exercise.

VW have tuned the 1.2 Tsi gets its max torque earlier in the rev range AND more power higher in the rev range compared to a normally aspirated 1.2

The power output is identical, the torque is what is making the difference between the two vehicles.

As I said, the 80-120 time is considerably improved between the Polo's with the same power but more torque

I have just checked, the Octavia 184 Tdi is 140kg heavier than the 1.8 Tsi so you are not making a direct comparison

Edited 2 October, 201510 yr by Bristolf2b

The 1.8 TSI is around 10% faster than the RS TDI on the 80-120 because it has the same power and 10% less weight. In fact, it has also a slightly better air penetration coefficient.

The fact the TDI has 52% more torque does not help it a bit.

 

What you call the torque is making the difference, is in fact the following.

A higher max torque for the same max power means the max power will be available sooner (undertsand at lower revs). 

When comparing a diesel and a petrol, that does not give any indication.

When comparing a turbo petrol with an atmospheric petrol that have both around the same max revs, it means the turbo petrol has its max power earlier and for a longer range in revs.

Based on its better power curve shape, it will be easier to design the gearbox ratios to bring the power to the wheels in most conditions.

Some basics:

The acceleration is the force devided by the mass: a=f/m

The force is the power devided by the speed: f=P/v

The power is the engine power reduced by the transmission efficiency ratio: P=0.85Pe

The gearbox is designed so that a gear ratio allows the engine to work in its max power range.

So you have a direct link between the max acceleration and the max engine power.

What could be the link between the max acceleration and the max engine torque?

I wonder what a visitor from (insert name of place with wonderful air quality) would think of our pollution levels? Perhaps they would go home and describe it to their friends as 'awful'.

 

 

 

Whenever I visit the UK, I always seem to leave with a blocked nose and a feeling of phlegm in the back of the throat and sometimes in the chest. It always clears up after a few days back home. I don't tell my friends it's awful though, it's just "different" to what we're used to, in a similar way to carpets in bathrooms and separate hot and cold taps on opposite sides of the sink *

 

( * just what is the secret to efficiently washing your hands with this system? Without having to find a plug and fill up the sink with water and then risk that any dirty particles you've washed off your hands can easily get picked up again as you remove hands from water. Honestly, it's a real puzzle for foreigners    )

UK pollution isnt that bad on the most part....the only time I ever really notice it is when I (v rarely) go to London....upon getting home I blow the hooter and all sorts of ****e comes out....all sooty, gritty and horrible.....whilst I love our capital because its steeped in history and its great to visit....I adamantly would never want to live there....I think working there would be bad enough.

I lived in Oxfordshire for many years until recently...was lovely other than my house was surrounded by rapeseed fields and I have severe Hayfever...suffered terribly every harvest.

Live on the south coast now....can see the sea from my house and havent experienced better air quality ever really. Nothing like a sea breeze.

I have just checked, the Octavia 184 Tdi is 140kg heavier than the 1.8 Tsi so you are not making a direct comparison

But the 1.8 TSI 4x4 has more or less the same performance as the 1.8 Fwd, with the added weight.

In the initial pickup from standstill, 4wd and Lower gearing allows the matching of performance in the artificial world of 0-60 times. The 4x4 will use more fuel.

Edited 3 October, 201510 yr by Bristolf2b

In fact, the 4x4 1.8 TSI gearbox provides longer gears (higher gear ratios) than the 1.8 TSI Fwd. 1st gear, especially,  is even longer than the one of the RS TDI!

The 4wd transmission will also result in more power loss due to more friction.

 

The reason why it matches the 1.8 TSI Fwd 0-100km/h acceleration is because of less slipping of the wheels (because of the 4 driving wheels iso 2) and thus reducing the rolling resistance coefficient at low speeds.

 

Note: I'm not talking of any slipping you can actually feel. There is always some slipping of a driving wheel. This is depending on the torque at wheel. With a 4WD, the engine power will be transmitted to 4 wheels instead of 2, so that the torque at each wheel could be reduced by a factor up to 2.

Consequently the slipping of the wheel is reduced. This slipping of the wheel is significantly impacting the rolling resistance coefficient and as such the friction.

Edited 3 October, 201510 yr by JPH0091

And it has slighty more torque, 280nm vs 250nm.

Feel this is getting more and more off topic with each post :/

And it has slighty more torque, 280nm vs 250nm.

Yes. Thus, the max power available from 4500 rpm to 6200 insta=e

And it has slighty more torque, 280nm vs 250nm.

 

Yes. Thus the max power is available from 4500 rpm to 6200 instead of from 5100 rpm to 6200 on the FWD.

With the 4x4, the 1.8 TSI provides a better power curve. It is not limited to the 250Nm engine torque due to the DSG7.

Feel this is getting more and more off topic with each post :/

 

Oh I don't know. I had a stab at striking up a plumbing-related conversation, and failed :p

This was noticed.

So back to the topic. In France and Belgium (at least) VAG has opened web sites where you can check if your car needs to be recalled or not, based on the VIN.

 

Apparently no O3 are impacted.

Aligned with the fact that EA189 diesel engine type was not installed on the O3.

Oh I don't know. I had a stab at striking up a plumbing-related conversation, and failed :p

Have you got any 22mm elbows I could borrow anyways glad I have a vrs tsi on order

Think we can safely assume all EU5 diesel EA288 Mk3 Octavias are safe from the scandal....it will affect a few Mk2's though no doubt.

...In a similar way to carpets in bathrooms and separate hot and cold taps on opposite sides of the sink. just what is the secret to efficiently washing your hands with this system? Without having to find a plug and fill up the sink with water and then risk that any dirty particles you've washed off your hands can easily get picked up again as you remove hands from water. Honestly, it's a real puzzle for foreigners   

To continue this deviation from the thread, I believe it stems from the fact that in the UK, low pressure hot water systems used to be the norm. Since it is not practical to blend mains pressure cold and low pressure hot, taps were traditionally separate. It's also cheaper that way, which might also have something to do with it. ;-)

Totally has

So sorry if I missed a thread, but have we had proper confirmation yet that our mk3's are not affected (diesel vrs)

Thanks!