[teaston]

I assume 0-60 times only tell half the story of 330d vs 335d, due to the 330d only having one turbo which is running out of puff just as the 335d's big turbo is just getting started?

[Tengocity]

Originally Posted by teaston

I assume 0-60 times only tell half the story of 330d vs 335d, due to the 330d only having one turbo which is running out of puff just as the 335d's big turbo is just getting started?

I guess in that the higher the speed then bigger a difference will become apparent, due to it being purely about power and not much to do with traction/driver techique. In the same way that I expect that the real difference from my remap will become more readily apparant when I'm on the autobahn on Monday!

[dopper99]

Originally Posted by teaston

I assume 0-60 times only tell half the story of 330d vs 335d, due to the 330d only having one turbo which is running out of puff just as the 335d's big turbo is just getting started?

Yes the 0-100mph figure is quite different too. I think its something like 11.5s vs 14s+.

[dopper99]

Originally Posted by dopper99

Yes the 0-100mph figure is quite different too. I think its something like 11.5s vs 14s+.

Actually 14s+ might be for the sdrive, not sure about figures for the xdrive.


But I have found a few 0-1000m figures . Seems the 330d xdrive is not a lot behind the 335d and I found figures for a M135i xdrive (obviously not UK model) but was surprised how close the 335d is.
These are all figures from BMWs own data sheets.

[teaston]

Originally Posted by dopper99

Yes the 0-100mph figure is quite different too. I think its something like 11.5s vs 14s+.

So it's 2 seconds quicker 60-100, that's quite a difference & must make the 335d a fair bit better for a road overtaking!

[dopper99]

Originally Posted by teaston

So it's 2 seconds quicker 60-100, that's quite a difference & must make the 335d a fair bit better for a road overtaking!

As I say, that might be for the sdrive 330d not xdrive, but see my post above.

[teaston]

According to this site the 330d xdrive has same 0-60 and slower 0-100 than the sdrive!


335dx 330dx 330ds

[Tengocity]

This gives a good comparison across 335i sdrive/xdrive, 330d sdrive/xdrive and 335d

[Tengocity]

Teaston, I'm using same website, but can't work out how to copy the image of all the data comparing the 5 cars- how do you do it?

[Tengocity]

Originally Posted by Tengocity

This gives a good comparison across 335i sdrive/xdrive, 330d sdrive/xdrive and 335d

The impact of xdrive on performance is much greater at higher speeds irrespective of whether you have a 335 or 330d, and it doesn;t look like there is all that much benefit lower down, but these are theoretical data in a simulation and clearly don't take in to account things like rainy days of course!

Looking at these it's hard to argue that the 330d is fast enough!

[teaston]

Originally Posted by Tengocity

Teaston, I'm using same website, but can't work out how to copy the image of all the data comparing the 5 cars- how do you do it?

Are you adding each car to the comparison? That's all I did then take screen shot.

[Tengocity]

Originally Posted by teaston

Are you adding each car to the comparison? That's all I did then take screen shot.

Yes, I had all 5 cars on one comparison. Not sure how to do that on a MacBook!

[DieselRocket]

Originally Posted by NISFAN

Sorry Daveyc, but this is not correct.

Torque at the wheels determines acceleration. So for example on your 330d, it produces maximum torque at say 2800rpm, therefore it will be accelerating faster in any particular gear at 2800rpm than it will at 4000rpm.

Where a higher revving engine benefits (like a 335i), is that it can do a higher road speed in a given gear.

So if we put a 330d and a 335i next to each other fitted with the exact same gear ratios. Assuming car weights and everything else is equal, the 330d will absolutely pulverise the 335i in a roll on.....until the 330d runs out of revs. It will then need an upward gear change (to a lower ratio - less torque amplification), where it's extra torque will be reduced through the gearbox. The 335i starts gaining because even though it has less engine torque, it is running a higher torque amplification through the gearbox....until the 335i needs a gear change.

Of course in reality the 335i will have a more optimised set of gear ratios, maximising torque amplification to achieve a high torque at the wheels.

Hi NISFAN,

You're dead right - I was talking rubbish. Holding constant torque and doubling the rpm would double the power, not the force. Not quite sure how I managed to say something that daft :-(

Good clarification on gearing - makes it really clear.

[jusdorange]

Originally Posted by Tengocity

This gives a good comparison across 335i sdrive/xdrive, 330d sdrive/xdrive and 335d

You didn't take a screenshot

You linked to the php

Which means, if someone has never visited the site, it's blank

Or if you just used it like me, it shows my most recent search

[teaston]

Originally Posted by Tengocity

Yes, I had all 5 cars on one comparison. Not sure how to do that on a MacBook!

Like dis:

[NISFAN]

Originally Posted by teaston

According to this site the 330d xdrive has same 0-60 and slower 0-100 than the xdrive!


335dx 330dx 330ds

I imagine you meant sDrive, but that makes perfect sense to me. The power to weight ratio for all three are as follows:

335d xDrive 183.6 hp/Ton.............actual 183.6 hp/ton

330d xDrive 153.1 hp/Ton.............169.7 hp/ton

330d sDrive 159.1 hp/Ton.............177.1 hp/ton

So bar the few tenths lost getting to 20Mph for the sDrive, it has the upper hand for the rest of the race against it's same engined xDrive version.

A 335d sDrive would have a power to weight ratio of 190 hp/ton and would smoke them all.

[teaston]

Originally Posted by NISFAN

I imagine you meant sDrive, but that makes perfect sense to me. The power to weight ratio for all three are as follows:

335d xDrive 183.6 hp/Ton.............actual 183.6 hp/ton

330d xDrive 153.1 hp/Ton.............169.7 hp/ton

330d sDrive 159.1 hp/Ton.............177.1 hp/ton

So bar the few tenths lost getting to 20Mph for the sDrive, it has the upper hand for the rest of the race against it's same engined xDrive version.

A 335d sDrive would have a power to weight ratio of 190 hp/ton and would smoke them all.

Yes i did mean the xdrive is slower than sdrive.

So is it just the weight that makes the difference, or are their greater power losses in the xdrive drivetrain as well?

[Tengocity]

Ok thanks, here goes again!

Left to right on the columns it is:

335i sdrive 335i xdrive 330d xdrive 335d xdrive 330d sdrive

[Tengocity]

Out of interest, whilst we can't see what a hypothetical 335d sdrive would do, we can see what the Alpina D3 estate would do, in both RWD and AWD formats, and to really show what petrol power can do I've chucked in the B4 in both formats:

[NISFAN]

Originally Posted by teaston

Yes i did mean the xdrive is slower than sdrive.

So is it just the weight that makes the difference, or are their greater power losses in the xdrive drivetrain as well?

Yes there are power losses in the xDrive, about 4 % is typical for a diff and drive shafts.

[bwrlane]

Originally Posted by NISFAN

Sorry Daveyc, but this is not correct.

Torque at the wheels determines acceleration. So for example on your 330d, it produces maximum torque at say 2800rpm, therefore it will be accelerating faster in any particular gear at 2800rpm than it will at 4000rpm.

Where a higher revving engine benefits (like a 335i), is that it can do a higher road speed in a given gear.

So if we put a 330d and a 335i next to each other fitted with the exact same gear ratios. Assuming car weights and everything else is equal, the 330d will absolutely pulverise the 335i in a roll on.....until the 330d runs out of revs. It will then need an upward gear change (to a lower ratio - less torque amplification), where it's extra torque will be reduced through the gearbox. The 335i starts gaining because even though it has less engine torque, it is running a higher torque amplification through the gearbox....until the 335i needs a gear change.

Of course in reality the 335i will have a more optimised set of gear ratios, maximising torque amplification to achieve a high torque at the wheels.

NISFAN, despite having reasonable background in physics, I struggle to understand the relationship between torque, gearing acceleration, speed and power in cars. A bit geeky but I'd be interested to see if anyone has set out the actual equations setting out how they interrelate.

Consider two engine speeds, 2000 and 4000rpm. Assume the torque is the same but at 4000rpm there is double the power. And double the speed in the same gear. According to your comment, the acceleration is the same (because torque at the wheels is the same). How can the acceleration be the same when at 4000rpm the power is double? What does double power actually mean if acceleration is the same?

I always thought a cycling analogy is helpful. The prop forward on a bike generates a lot of torque because of his strong legs. But not being the lithest specimen, his power is limited due to his low pedal speed.

[NISFAN]

Originally Posted by bwrlane

NISFAN, despite having reasonable background in physics, I struggle to understand the relationship between torque, gearing acceleration, speed and power in cars. A bit geeky but I'd be interested to see if anyone has set out the actual equations setting out how they interrelate.

Consider two engine speeds, 2000 and 4000rpm. Assume the torque is the same but at 4000rpm there is double the power. And double the speed in the same gear. According to your comment, the acceleration is the same (because torque at the wheels is the same). How can the acceleration be the same when at 4000rpm the power is double? What does double power actually mean if acceleration is the same?

I always thought a cycling analogy is helpful. The prop forward on a bike generates a lot of torque because of his strong legs. But not being the lithest specimen, his power is limited due to his low pedal speed.

It is an interesting topic.

The basic equation is of course Newton's own: Force = Mass x Acceleration

Force being the driving force at the wheel, specifically at the contact point of the tyre with the road.

With this in mind, regardless of how important I made engine torque sound, it is largely irrelevant. That is why engine power is a more meaningful metric.

If you build the picture, the engine applies it's torque to a gearbox, which in the first few gears at least amplifies the torque.

Lets take a hypothetical 500lb.ft engine.

First gear might typically have a ratio of 3:1 which amplifies the 500lb.ft to 1500lb.ft. Ignoring any losses of course in this whole example.

This 1500lb.ft then goes through the rear diff and might see another amplification in the order of 3:1. So now we have 4500lb.ft travelling towards the wheels.

The wheels then reduce the torque, due to the diameter difference between the drive shaft and the outer circumference of the tyre. Quite massively as you might imagine as there is something like a 26:1 difference.

The equation to arrive at what actually moves the car forward is a fairly simple one, albeit long as it has many equations to get from engine to forward movement.

The real clue about power being more important comes when we consider what it actually means on a practical level. As you know torque and power are mathematically linked with this equation: HP = Torque x RPM / 5252. So a higher horsepower engine basically means it has the ability to do more work.

Note that with gears we can trade torque for revs and vice versa. And that is how a 300lb.ft Petrol engine can out accelerate a 500lb.ft Diesel (assuming the petrol has a higher peak horsepower figure). In effect the gearing nullifies the actual crank torque figure, making horsepower a more meaningful parameter.

In your example of an engine making the same torque at double the revs, if torque was a completely flat parameter, so 500lb.ft all the way through the rev range, both your examples could run the same first gear ratio, and acceleration would be exactly the same. Of course the one that stops at 2000rpm will require a gear change at half the road speed, where it will drop into a 'less amplified torque' gear ratio, meaning it's rate of acceleration drops, whilst the high revver continues at 1st gear torque amplification gearing. When it gets to needing a second gear, that could be a much 'closer ratio' than on the low revver, meaning it gains an advantage with every gear change.

Hope that makes sense.