[JOHNBMWM5]

Originally Posted by MaestroAl

You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [I]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

Simples

Explained in the "nicest way" but true, and torque is what I like.

[JOHNBMWM5]

Originally Posted by MaestroAl

Actually, I think I understand what you meant by "performance indicator". Inasmuch as a higher bhp figure is an indication that a car develops high torque at high rpm then yes, it is a good indicator of "performance".

But let's not forget that this is all in the context in which it was intended. The rate of acceleration is only ever governed by torque. Ever. The rate of acceleration is what makes a car feel quick to the driver, it is all we're aware of in terms of straight line performance as a driver. A car like the 30D will always feel quick in any gear whereas cars like the 335i and M3 will never "feel" as quick because they can never have the same amount of torque applied to the drivetrain. Thanks to gearing, they will be empirically quicker when driven in the higher rev ranges where they shine and as I've always said: they'd leave a 30D behind but again, nobody drives like that in the real world and they have to be driven like that to be as quick as a 30D - and will never feel as quick unless you're booting it at 7000rpm in third or something: an experience you can't match in a diesel.

So since these kind of cars require effort, revs and a lot of fuel to match the 30D's performance and even more to surpass it, in the real world of on-road driving, the 30D is the quicker car and torque is more important than horsepower.

QED

Agreed my E90 2010 M3 never felt fast till it's neck was being wrung and then I had to have one eye up my arse for the boys in blue.
It meant fastish driving and having a "Quick Squirt " when all was clear, this did get tiresome, I had much more fun in the F10 550i MSport as the torque was just immense.

[dopper99]

Blimey, didnt realise the 550i has soooo much torque. Best of both worlds - torque AND power....

550i
600Nm 442 lb-ft

(but 407bhp)


330d
560Nm 413 lb-ft


no-where near and economical though as 27mpg vs 57mpg

[TMP]

Originally Posted by MaestroAl

You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [I]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

Simples

I look at 0-60 time to be honest. As that is a result of both torque and power.

So, torque is what pushes yo back in the seat and power is how long that push lasts and at what multiple.

Dude, you have a great, probably the best all-round car , buts saying its going to beat an M3 even in top gear ain't going to happen.

Why, well if its an auto it would kick down or the guy driving it would change gear

[MaestroAl]

Not in an auto, obviously But yeah, 50mph in top gear ... the 30D would pull ahead. No doubt.

[TMP]

Originally Posted by MaestroAl

Not in an auto, obviously But yeah, 50mph in top gear ... the 30D would pull ahead. No doubt.

and is your car a manual

i think if i tried this in the M135i, it wold drop 6 cogs,
(altough in manual mode, it doesnt kick down thank god!)

[JOHNBMWM5]

Originally Posted by dopper99

Blimey, didnt realise the 550i has soooo much torque. Best of both worlds - torque AND power....

550i
600Nm 442 lb-ft

(but 407bhp)


330d
560Nm 413 lb-ft


no-where near and economical though as 27mpg vs 57mpg

Yep I got 27MPG out of mine.

[JOHNBMWM5]

Originally Posted by TMP

and is your car a manual

i think if i tried this in the M135i, it wold drop 6 cogs,
(altough in manual mode, it doesnt kick down thank god!)

TBH the 550i M Sport was almost as quick as the E90 M3 in a straight Line.

[MaestroAl]

there's no substitute for displacement

[NISFAN]

Originally Posted by MaestroAl

Actually, I think I understand what you meant by "performance indicator". Inasmuch as a higher bhp figure is an indication that a car develops high torque at high rpm then yes, it is a good indicator of "performance".

But let's not forget that this is all in the context in which it was intended. The rate of acceleration is only ever governed by torque. Ever. The rate of acceleration is what makes a car feel quick to the driver, it is all we're aware of in terms of straight line performance as a driver. A car like the 30D will always feel quick in any gear whereas cars like the 335i and M3 will never "feel" as quick because they can never have the same amount of torque applied to the drivetrain. Thanks to gearing, they will be empirically quicker when driven in the higher rev ranges where they shine and as I've always said: they'd leave a 30D behind but again, nobody drives like that in the real world and they have to be driven like that to be as quick as a 30D - and will never feel as quick unless you're booting it at 7000rpm in third or something: an experience you can't match in a diesel.

So since these kind of cars require effort, revs and a lot of fuel to match the 30D's performance and even more to surpass it, in the real world of on-road driving, the 30D is the quicker car and torque is more important than horsepower.

QED

Hmmmmm, it is a complicated issue this hp and torque thing. (To explain it I think of the following)

Whilst true that torque is the rotating dynamic that dictates ultimate force levels, it is horsepower that we are interested in. Torque is a rotational force and horsepower is the same force expressed in a linear form. Horsepower is easier to grasp if we imagine that there is a drum attached to the flywheel, and we use that drum to wind up a rope (linear movement). The torque determines the force of pull on the rope, horsepower determines the rate at which the end of the rope moves, the faster the drum, the faster the rope.

Now you can debate till the end of time which is more important, but remember that gearing determines the torque applied to the wheel, and that is the single most important factor, more important than the torque developed at the flywheel. We can trade low flywheel torque for high wheel torque and vice versa.

Now if we go back to an engine driving a drum with our rope. Imagine instead of laying the rope on the ground we hang it over a cliff and add a weight to the end of it. A 330D could pull a large diameter drum but at low revs (high torque/lowish power) versus a F1 engine which because it doesn't have much torque, would have to have a small diameter drum attached to it to pull the resistance in our rope, but because it can rotate the drum at very high speed, will win the race.

A torque/gearing chart comparing 335i vs 330D would be very interesting

[NISFAN]

Originally Posted by MaestroAl

there's no substitute for displacement

No no no.....there is no substitute for boost pressure

[MaestroAl]

Originally Posted by NISFAN

No no no.....there is no substitute for boost pressure

Noooo no no no - there is no substitute for heavily boosted displacement

[NISFAN]

Originally Posted by MaestroAl

Noooo no no no - there is no substitute for heavily boosted displacement

Deal

[MaestroAl]

AMG it is then

[HighlandPete]

This topic has moved on a bit ....

Here's a bit of comment I put together several years ago on this subject of torque and power. Kept it simple in the sense it uses two petrol NA engines, but in a way the variables get balanced out. Ignoring the dynamics of the chassis, in this instance we can just choose the engine we prefer, the more relaxed drive, or an engine we'd enjoy revving. Much the same as the diesel vs petrol choice we have.

To illustrate that torque can’t be seen in isolation from power, or even power to weight ratios and gearing.

Take two petrol cars, with totally different power deliveries. Both E39 touring models, one a 540i 4.4-litre auto, the other an Alpina B10 3.2-litre manual. So we have lots of variables.

Back to back (group) tested by AutoCar.

0 – 60 mph: both cars, 6.2sec
0 - 100 mph: both cars, 15.9sec
30 - 70 through the gears: 540i 5.6sec; Alpina 5.5sec
Standing ¼ mile: both cars, 14.8sec/97mph

Alpina: 260bhp/5,900rpm; 243lb/ft @ 4,300rpm
540i: 286/5700rpm; 310lb/ft @ 3900rpm

Alpina: Power to weight; 160bhp/tonne
540i: Power to weight; 160bhp/tonne

Alpina: Top speed: 157mph unrestricted
540i: Top speed; 155mph limited. I’ve read the 540i model tested tops out at 157/158mph unrestricted.

Alpina: Gearing: 25.7mph per 1,000rpm. Max speed @ 6,000rpm; 5th gear.
540i: Gearing: 33.5mph per 1,000rpm. Max speed (limited) 5,780rpm; 4th gear.

OK, the 330d and 335i won't fit that same model, but we still need the full rev range of each, to get maximum performance. But like our diesels, the 540i is the car that would feel 'stronger' in average day to day driving.

On a side note, big torque figures are fine in the diesels, but I wonder how far we can go before even the 'torque pulse' controls like the DPF, (now virtually the same technology included in the torque converter) will be either so heavy duty, or asking for even more advanced technology to give smoothness and longevity? We already have the torque values pushing the MT into the background, as the manual gearbox internals need to be so beefed up to carry the torque figures.

HighlandPete

[dopper99]

Originally Posted by TMP

....Dude, you have a great, probably the best all-round car , buts saying its going to beat an M3 even in top gear ain't going to happen.......

I wouldnt be so sure about that.

With regards to the figures I posted earlier in this thread that I copied from an old E90 brochure, I think there is a misprint and these should be 50 -75mph.

The reason being is that is on the next page in the brochure it says "50 to 75mph is equal to 80 to 120km/h" and refers back to the figures below. So I think they cocked up in the brochure. Also BMW only refer to 50 - 75mph on their website as well as other PDF's I have.

Originally Posted by dopper99

E90 Manual 330d LCI 245bhp
55-75mph in 4th: 4.8
55-75mph in 5th: 6.1

E90 Manual 335i
55-75mph in 4th: 5.3
55-75mph in 5th: 6.3

Why do I mention this? Well take a look at the 50-75mph for an M3 coupe:

http://www.bmw.co.uk/bmwuk/pricesand...calSpec&isPGA=

50-75 in 4th: 4.9

So slower than an E90 330d like-for-like manual in 4th gear. Backs up what MaestroAl has been saying. Enough said.


Edit: in fact the data for the old 330d coupe is on the website:

http://www.bmw.co.uk/bmwuk/pricesand...calSpec&isPGA=

330d coupe 50-75 in 4th: 4.7 (coupe is usually a fraction quicker - but compares to the above M3 coupe ).

[JOHNBMWM5]

I think for the "Layman" my next statement should simplify the comparison.
High torque = "unstressed" driving
Low torque = "Stressed".

[HighlandPete]

Originally Posted by dopper99

So slower than an E90 330d like-for-like manual in 4th gear. Backs up what MaestroAl has been saying. Enough said.

We certainly can't deny the figures. Most diesels are by nature going to return better incremental times in the higher gears. For the bigger picture we get back to gearing, don't we, and the arbitrary incremental times. To be fair most M3 drivers won't have any aversion to snatching a lower gear. In fact that is the bit they likely love best, the chance to open it up a bit in day to day driving.

It reminds me of the car that does 0 - 60 in a time faster than its competitor, so the feeling it is the faster car. But it may be as simple as one car gets to 60mph with one gear change, the other needs two changes. Change the goal posts to 0 - 70, and the competitor could be the faster.

To be honest the feel of an engine's delivery, the flexibility, the way it's geared can make it a car of choice, as much as outright performance and headline figures. Hence why many will really enjoy the 330d diesel.

I was in a position where I had the choice of a 530d or 535i, neither purchase or running costs is the issue. I just preferred the 535i as a car, as a package, and how it will be used, rather than the 530d. How I drive, the 535i does not lack one little bit over the diesel.

If my driving conditions were different I'd most likely be in the diesel. A lot of my trips are about 12 miles, most of it cruising. I have two accelerations to 60mph in 11 miles. If I was contending with constant variables, that would swing the type of engine I would prefer. Each to his own, isn't it.

HighlandPete

[dopper99]

Originally Posted by HighlandPete

.... Each to his own, isn't it....

That sums things up well.
There is nothing wrong with pretty much any engine from BMW. Both their petrol and diesels are awesome - in their different ways and there is no "right" or "wrong" engine. Its all down to personal preference really and other factors such as people's mileage etc....

It's nice to be on a forum and not end up in the usual slanging match of petrol vs diesel, unlike other forums.

[MaestroAl]

Indeed. Try having the same conversation in the main forum though

[TMP]

Originally Posted by dopper99

I wouldnt be so sure about that.

With regards to the figures I posted earlier in this thread that I copied from an old E90 brochure, I think there is a misprint and these should be 50 -75mph.

The reason being is that is on the next page in the brochure it says "50 to 75mph is equal to 80 to 120km/h" and refers back to the figures below. So I think they cocked up in the brochure. Also BMW only refer to 50 - 75mph on their website as well as other PDF's I have.



Why do I mention this? Well take a look at the 50-75mph for an M3 coupe:

http://www.bmw.co.uk/bmwuk/pricesand...calSpec&isPGA=

50-75 in 4th: 4.9

So slower than an E90 330d like-for-like manual in 4th gear. Backs up what MaestroAl has been saying. Enough said.


Edit: in fact the data for the old 330d coupe is on the website:

http://www.bmw.co.uk/bmwuk/pricesand...calSpec&isPGA=

330d coupe 50-75 in 4th: 4.7 (coupe is usually a fraction quicker - but compares to the above M3 coupe ).

But as Highland Pete said, you cant assume 4th gear is the same in both cars (and it is not).

Plus, as I said early do we really think a 8k rev loving petrol driver is going to stay in 4th gear....nope
(And having been on a track in my 330d vs a M3, i can personally vouch to the above!)

Finally, as you said - each to there own

[MaestroAl]

Don't forget that nobody is saying that a 30D is as fast as an M3 (or even a 35i) on full reheat, going through the gears. Just that in "normal" driving, when you're not wringing its neck, it's quicker in real terms because of the engine characteristics and where the torque is.