RE: PH Fleet: Porsche Panamera Diesel

[Kolbenkopp]

caraddict said:

Yes, I really think so. I always wanted a proper GT some day, and this so far the best car because:
- whenever I'm traveling, I often have the need to carry passengers with me.
- the boot is decent size.
- I like to drive more than filling up.
- the interior is lovely to my eyes.
- 250 hp is enough for me, I'm not spoiled with power.
- two extra doors are great for passengers getting in and out of.

It is going to cost more than 5k in depreciation a year -- if you keep it for a decade. And while it is most certainly a very very good car, I doubt that in the real world it will be much better than say a 530d.

7 to 10k running costs a year could be better spent IMVHO. Get your party on a plane, rent Panamera on arrival and have a cute au-pair to do the bookings. Going to be faster and cheaper and better to look at in the end .

[DonkeyApple]

JS100 said:

Were you bullied at school or something? There really are more ways to enjoy your life than trying to annoy people.

No, when I was at school I learned to read. Stroker.

[fluffnik]

Stuart said:

I asked by what objective measure it could be considered slow.

I'm not convinced, fuel stops included, that it could stay with a D5 (Touring) cross country...

...I'd love to check carefully though.

I'm available for trans-Alpine testing at short notice.

[JS100]

DonkeyApple said:

No, when I was at school I learned to read. Stroker.

Congratulations - your parents must have been proud of you Stroker.

[DonkeyApple]

JS100 said:

Congratulations - your parents must have been proud of you Stroker.

Hey ho. You seem annoyed. This is a good thing.

Learn to read and stop being such a fag.

[RenesisEvo]

E38Ross said:

Eg - diesel max rpm 5k,petrol 7k. Both have top gear going to 200mph say. Put foot down at 80mph (40% max rpm) in each car.

Diesel - (405x2k) / 5252 =154bhp
Petrol - (295x2800) / 5252 = 157bhp.

But oh, the diesel has more torque so must be quicker "in gear"

Its the torque that accelerates the car, not the horsepower (the power being simply the rate at which the torque is made). Torque = inertia x angular acceleration (then resolve at the contact patch using Newton's 2nd law). But I really think this is starting to circle and I don't see value in continuing.

What I will say, is that I struggle to comprehend how a car that is roughly a third heavier than mine own (which is not slow, but not really fast), but with nearly 100% more torque, can be described as slow.

[Johnboy Mac]

Stuart said:

There are plenty of things it is "not as fast as" but that by itself does not mean that it is slow.

^^^An 'interesting' use of words that seem rather meaningless. I'd expect better from someone who works for a motoring organ.

The facts are it's slow for the money, it's slow for a Porsche and the engine is not special enough either. As I said earlier it's laughable that a low power version of an Audi engine is employed (just because nothing else fits), after all it's not a humble 924 we're talking about. Forget about my opinion/view, just look at Car magazine's article for example, also their group test. I can't exactly recall the articles but it wasn't great and certainly nothing like Mr.Harris's glowing report.

Then again I suspect that you Mr.Stuart automatically feel that you have to support a colleague by virtue of the fact you both work for the same company, thus your comments, which could be viewed as biased in this thread.

Happily stand to be corrected on all counts.

[E38Ross]

RenesisEvo said:

Its the torque that accelerates the car, not the horsepower (the power being simply the rate at which the torque is made). Torque = inertia x angular acceleration (then resolve at the contact patch using Newton's 2nd law). But I really think this is starting to circle and I don't see value in continuing.

What I will say, is that I struggle to comprehend how a car that is roughly a third heavier than mine own (which is not slow, but not really fast), but with nearly 100% more torque, can be described as slow.

I thought it was power at the wheels that accelerates the car. If that's not the case, why is an E60 M5 much quicker than this? And why are petrol cars with more power but less torque quicker than diesels?

[RenesisEvo]

E38Ross said:

I thought it was power at the wheels that accelerates the car. If that's not the case, why is an E60 M5 much quicker than this?

It is, but what is power? Mechanically speaking, it is work being done over a finite time period. In this case, the work being done is the torque being applied (Power = Torque * angular velocity, as you stated), and it's the torque that causes the drivetrain to be rotated, which causes the wheels to turn. The gear ratios multiply or divide the torque as a trade-off with angular velocity. This applies a force at the contact patch (since torque is the product of force and radius) which acts to accelerate the car against its mass and rolling resistance (and at higher speeds aero drag). So even with the same torque/power on paper, you can have quite a different resultant force being applied at the contact patch. The E60 M5 is probably a fair bit lighter than a Panamera, but I haven't got any stats to hand.

E38Ross said:

And why are petrol cars with more power but less torque quicker than diesels?

Gearing is the biggest reason - both gearbox and final drive ratios. This is why traditionally revvy, 'torque-less' Honda VTEC-powered cars are still actually quite quick. If you don't have the torque, you chose a shorter gear ratio overall (from engine to tyre rotation), which is fine because a diesel typically gives up by 4000rpm (due to the limitation of the speed of the flame front when burning diesel), a petrol can keep going for at least another 2000, much more usually. Secondly - inertia. For example, diesel engines typically have heavier components, these have more inertia, so are less responsive to changes in rotational speed - e.g. blip the throttle on a diesel and it's generally is much less responsive. The other problem is we only ever quote peak values, not the ranges over which those figures are available, which makes a big difference to the choice of gearing and how the car accelerates in-gear. There's a lot more to consider - there's so many variables to account for.[/footnote]

Edited by RenesisEvo on Wednesday 22 August 23:12

[Robb F]

RenesisEvo said:

Its the torque that accelerates the car, not the horsepower (the power being simply the rate at which the torque is made).

Yeah that's why traction engines are so fast.

[RenesisEvo]

Robb F said:

Yeah that's why traction engines are so fast.

Not sure I understand you. And again, gearing.

[fluffnik]

RenesisEvo said:

Its the torque that accelerates the car, not the horsepower (the power being simply the rate at which the torque is made). Torque = inertia x angular acceleration (then resolve at the contact patch using Newton's 2nd law). But I really think this is starting to circle and I don't see value in continuing.

It's the torque at the wheel, as resolved, that counts, not at the flywheel...

RenesisEvo said:

What I will say, is that I struggle to comprehend how a car that is roughly a third heavier than mine own (which is not slow, but not really fast), but with nearly 100% more torque, can be described as slow.

The force available at the contact patch at any given speed will vary with (geared) RPM; it's the area under the part of the curve where the gearbox lets you live that counts.

Try a CVT Micra some day...

Edited by fluffnik on Wednesday 22 August 23:41

[fluffnik]

RenesisEvo said:

And again, gearing.

...in other words, POWER.

I drive a moderately revvy non stump-plugging V8 and I entirely compensate for its lack of low end torque by revving it out in intermediate gears and pre-emptively changing down in anticipation of high power requirements.

I fully intend to replace it at some point with an eight-speed D5 whose gearbox will entirely compensate for any narrowing of power bands by staying in the sweet spot always...

Neither peak torque nor peak power count for much, it's the area under the curve and the gearbox's ability to keep you in a fat bit that matters.

[E38Ross]

RenesisEvo said:

E38Ross said:

I thought it was power at the wheels that accelerates the car. If that's not the case, why is an E60 M5 much quicker than this?

It is, but what is power? Mechanically speaking, it is work being done over a finite time period. In this case, the work being done is the torque being applied (Power = Torque * angular velocity, as you stated), and it's the torque that causes the drivetrain to be rotated, which causes the wheels to turn. The gear ratios multiply or divide the torque as a trade-off with angular velocity. This applies a force at the contact patch (since torque is the product of force and radius) which acts to accelerate the car against its mass and rolling resistance (and at higher speeds aero drag). So even with the same torque/power on paper, you can have quite a different resultant force being applied at the contact patch. The E60 M5 is probably a fair bit lighter than a Panamera, but I haven't got any stats to hand.

E38Ross said:

And why are petrol cars with more power but less torque quicker than diesels?

Gearing is the biggest reason - both gearbox and final drive ratios. This is why traditionally revvy, 'torque-less' Honda VTEC-powered cars are still actually quite quick. If you don't have the torque, you chose a shorter gear ratio overall (from engine to tyre rotation), which is fine because a diesel typically gives up by 4000rpm (due to the limitation of the speed of the flame front when burning diesel), a petrol can keep going for at least another 2000, much more usually. Secondly - inertia. For example, diesel engines typically have heavier components, these ve more inertia, so are less responsive to changes in rotational speed - e.g. blip the throttle on a diesel and it's generally is much less responsive. The other problem is we only ever quote peak values, not the ranges over which those figures are available, which makes a big difference to the choice of gearing and how the car accelerates in-gear. There's a lot more to consider - there's so many variables to account for.[/footnote]

Edited by RenesisEvo on Wednesday 22 August 23:12

What you've just explained, about gearing etc, proves my point, not yours. You seemingly were getting confused with torque at the flywheel not at the wheels.

An M5 weighs similar to the panamera, not lighter to make is so much faster.

[E38Ross]

fluffnik said:

RenesisEvo said:

And again, gearing.

...in other words, POWER.

Thank you. Why does it seem so many on PH Think diesels are so fast because of peak torque, totally ignoring gearing and rpm and the fact they don't rev as high. People seen to get confused about the characteristics of diesel vs petrol, and turbo charged engines. It's not diesels that give the flat torque curves, it's the turbo charger. Look at turbo charged petrol, they have similar curves to the diesel.... Just less torque but over a much wider band.

[DonkeyApple]

[redacted]

[MGJohn]

[redacted]

[ewenm]

It's the "area under the curve" rather than "maximum point on the curve" difference.

It doesn't really matter how high the peak is if the area under the curve is tiny (so a very peaky engine). Torque/Power spread is more important than peak torque/power in most driving.

[GuyS.]

Let me throw my 2 bob into the 'is the diesel Panamera slow' debate; I'm now in my 3rd year of owning a Panamera Turbo and I'm still very happy with the car, thanks for asking. Back in January when my car was in for its first 2yr/20k service I was lent a Panamera diesel as a courtesy car for the two days it took the OPC to change the oil in mine. Sure, the diesel lacks the frankly silly acceleration the turbo has, but at no point did I think it felt 'slow', the mid range punch was impressive. Whether that is down to torque or power you'll have to excuse my ignorance here, during my O level physics classes I used to sit next to a girl with wonderful charlies and generally my mind was on other things.

One more thing I will add, I actually preferred the ride of the diesel which was on 19" rims and standard springs compared with my turbo which has 20" wheels and clever self levelling air suspension etc.

[Cobnapint]

carnut360 said:

well its a car that certainly has grown on my still not sure about the rear but then again didn't much like the 928..BUT..why not choose the Cayenne Diesel, i bought mine fully speced and only paid 55k it does around 40 mpg on uk journeys or when i drive to switzerland does 36mpg...i even towed my caterham to brands hatch and back on a trailer and it did 31 mpg.

Its so comfortable great long distance cruiser and pretty nippy to overall i would definatly recomend the cayenne diesel over the panamera as its also 4wd.

buy one and you will be hooked!

Agreed. I've just travelled up from the East Mids to Northumberland in mine and I cannot think of any of my previously owned cars that I would rather have done the journey in. Smooth, quick, quiet, and yes - torquey.

I was never a fan of the Cayenne until I actually borrowed one, so I can see where Chris is coming from in his excellent Panamera review. And I feel sorry for those that haven't quite grasped the 'torque' thing yet. I've owned cars that have had high power figures with relatively low torque figures, and it does mean that you have to rev the nuts of the things to feel like you're getting somewhere. Fine on a track, but with one of the latest diesels, real world driving is a far better place to be.
Years ago I would never have considered a diesel, but now I'm a convert.