Is torque really relevant?

[Welshbeef]

If say from 30mph to 60 or 70mph in 3rd gear in the 535d WOT let’s say existing a 30mph straight into a dual carriageway or (assuming speedo over reads 60mph by 10mph...) you’d need a very fast car following it to be able to overtake cleanly whilst keeping within the 70mph limit.

Very challenging.

A Tesla would might do it not sure what else could - maybe the following car would need to nip into 1st and flat out attack to achieve the challenge

[StuntmanMike]

otolith said:

cerb4.5lee said:

As a general rule I much prefer lots of torque and a turbo in a daily, but I'm happy enough with high revs and not much torque in a weekend fun car though.

For example I didn't like my E92 M3 as a daily, but I'd be very happy with it to use occasionally on nice clear roads though for sure.

Perceptions are interesting, though - the butt-dyno is unreliable!



(lower trace standard E92 M3)



(standard E92 320d)

The M3 chart is not in the least bit accurate and looks like it’s been manipulated to flatter the car!

If that was my M3 I would ask for my money back.

[otolith]

Welshbeef said:

The BMW 320d whilst clearly having less torque and BHP at normal road driving speeds with normal revs it will actually have MORE torque (I didn’t check the power) than the E92.

Torque at the crank at a given road speed is meaningless without knowing the gearing.

[otolith]

StuntmanMike said:

otolith said:

cerb4.5lee said:

As a general rule I much prefer lots of torque and a turbo in a daily, but I'm happy enough with high revs and not much torque in a weekend fun car though.

For example I didn't like my E92 M3 as a daily, but I'd be very happy with it to use occasionally on nice clear roads though for sure.

Perceptions are interesting, though - the butt-dyno is unreliable!



(lower trace standard E92 M3)



(standard E92 320d)

The M3 chart is not in the least bit accurate and looks like it’s been manipulated to flatter the car!

If that was my M3 I would ask for my money back.

All of the M3 graphs look similar.

[nomis36]

For those saying diesels have a very narrow power band I present to you my 330d. It pulls hard from 1500 to the red line.
https://youtu.be/NJ3RVOzIQ5g

[julian64]

nomis36 said:

For those saying diesels have a very narrow power band I present to you my 330d. It pulls hard from 1500 to the red line.
https://youtu.be/NJ3RVOzIQ5g

I also think its good the way BMW hides all the tinny clattery sound of that diesel engine with their augmented in cabin stereotainment.

[Fastdruid]

nomis36 said:

For those saying diesels have a very narrow power band I present to you my 330d. It pulls hard from 1500 to the red line.
https://youtu.be/NJ3RVOzIQ5g

No it doesn't because

a) It doesn't *get* to the red line (honestly people shouldn't post things that disprove their own arguments). It gets nearly there once.
b) The redline is only at 4800rpm anyway...which means by definition it's a narrow power band.

From that video

Redline is 4800

Change 1 - 4600
Change 2 - 4350
Change 3 - 4700

If you take my car (which makes a smidge less power and a lot less torque than the 330d) I've got ~5mph more in 1st, ~10mph in 2nd and ~15mph in 3rd. Theoretically I could do 0-100 with two gear changes but that's taking it deep into the red to the limiter (redline 6500, limiter is at 7k).

As a nice example of the difference and how/why diesels *DO* have a narrow power band this is a nice graph of a 320d vs a 328i



The 320d produces more _peak_ but the 328i produces a *MUCH* wider spread.

[MC Bodge]

Fastdruid said:

No it doesn't because

a) It doesn't *get* to the red line (honestly people shouldn't post things that disprove their own arguments). It gets nearly there once.
b) The redline is only at 4800rpm anyway...which means by definition it's a narrow power band.

From that video

Redline is 4800

Change 1 - 4600
Change 2 - 4350
Change 3 - 4700

If you take my car (which makes a smidge less power and a lot less torque than the 330d) I've got ~5mph more in 1st, ~10mph in 2nd and ~15mph in 3rd. Theoretically I could do 0-100 with two gear changes but that's taking it deep into the red to the limiter (redline 6500, limiter is at 7k).

As a nice example of the difference and how/why diesels *DO* have a narrow power band this is a nice graph of a 320d vs a 328i



The 320d produces more _peak_ but the 328i produces a *MUCH* wider spread.

The D gearing is longer...

[Fastdruid]

MC Bodge said:

Fastdruid said:

No it doesn't because

a) It doesn't *get* to the red line (honestly people shouldn't post things that disprove their own arguments). It gets nearly there once.
b) The redline is only at 4800rpm anyway...which means by definition it's a narrow power band.

From that video

Redline is 4800

Change 1 - 4600
Change 2 - 4350
Change 3 - 4700

If you take my car (which makes a smidge less power and a lot less torque than the 330d) I've got ~5mph more in 1st, ~10mph in 2nd and ~15mph in 3rd. Theoretically I could do 0-100 with two gear changes but that's taking it deep into the red to the limiter (redline 6500, limiter is at 7k).

As a nice example of the difference and how/why diesels *DO* have a narrow power band this is a nice graph of a 320d vs a 328i



The 320d produces more _peak_ but the 328i produces a *MUCH* wider spread.

The D gearing is longer...

It has to be, because it has a narrower rev range

For any equivalent state of tune diesel vs petrol cars (which is very very rare in part due to BMW's tendency of grouping similar _power_ rather than similar state of tune into their monikers) it means that at any speed outside first the petrol can be in a lower gear giving more torque at the road.

Of course as ever everyone compares their 3l twin turbo diesel to a 2l NA petrol they drove 20 years ago or the hire car 1.6i...equally I'm as guilty of comparing 2.0T, 2.3T and 2.5T vs 2.0TDCI.

[V8RX7]

nomis36 said:

For those saying diesels have a very narrow power band I present to you my 330d. It pulls hard from 1500 to the red line.
https://youtu.be/NJ3RVOzIQ5g

1500 to 4500 in that vid so 3000rpm

You are joking ?

You understand that many petrols pull from 1500 - 7500 or more - which would be 6000rpm so double yours

Am I missing the whoosh ?

[LG9k]

I did a comparison a few years ago of a torque-less wonder Honda S2000, with a BMW 320 and an Audi A4 diesel. I took the power curve figures from rototest.com and put these charts together. I'm not entirely sur they make total sense, so happy to stand corrected...

First, the power and torque curves:




Now, plotting those same lines as a percentage of peak rpm, this gets us to somewhere near a comparison of "power bands":


I also calculated "gear adjusted torque" figures - what this does is assumes similar speeds in each gear. To explain this, I've looked at maximum rpms for each engine and created a ratio. As the S2000 has peak rpms of 8,815 in the data versus 4,407 for the A4, the ratio applied to the S2000 is 1, and 2 for the A4.
In other words, if travelling at, say 40mph in top gear, the S2000's engine will have twice as many rpms as the A4.
I think this is a representation of "Torque at the wheels"(?)



And now plotting those figures as a percentage of peak rpm:



Here's a table of some 3-series figures (also from a few years back):

Model	Price	PowerHP	TorqueNm	Weightkg	Power/Weight	Torque/Weight	0-62Secs	50-754thSecs
320i	26,305	170	210	1435	118	146	8.1	8.1
325i	29,205	218	270	1495	146	181	6.6	7.2
330i	32,435	272	320	1545	176	207	6	6.1
335i	34,430	306	400	1600	191	250	5.5	5.2
320d	28,530	177	350	1495	118	234	7.9	6.6
325d	30,430	197	400	1590	124	252	7.3	6.3
330d	33,025	245	520	1600	153	325	6	4.7
335d	36,495	286	580	1645	174	353	5.9	n/a
M3	50,935	420	400	1655	254	242	4.8	4.9

Here are the correlation co-efficients
Correlations
Power to weight vs 0-62 0.95
Power to weight vs 50-75 0.63
Torque to weight vs 0-62 0.55
Torque to weight vs 50-75 0.91

When looking at the measure of outright acceleration in the "optimum gears", we see a 95% correlation to Power-to-weight. For driving in the "wrong" gear, the torque-to-weight has an 91% correlation to the 50-75 time.

However, there is a stronger correlation of power-to-weight against the 50-75 time than there is for the torque-to-weight 0-62 time.

What is also interesting is looking at where the "to-weight" figures are the same.

1) The 320i and 320d both have the same power-to-weight but the d is faster to 62, because it produces a greater percentage of its peak power throughout the rpm range.

2) The 335i and the 325d have near enough the same torque-to-weight figure but the 335i is much faster in terms of both measurements, because it has a far superior power-to-weight ratio. The M3 is similar in terms of torque-to weight as both of these, although slightly lower, but is again faster on both counts because of the power.

All interesting stuff.

Discuss (or tell me my thinking is totally flawed!

Edited by LG9k on Wednesday 8th July 16:39

[TheDrBrian]

Fastdruid said:

No it doesn't because

a) It doesn't *get* to the red line (honestly people shouldn't post things that disprove their own arguments). It gets nearly there once.

Only sith deal in absolutes. BMW owners like “abouts”

[Welshbeef]

V8RX7 said:

nomis36 said:

For those saying diesels have a very narrow power band I present to you my 330d. It pulls hard from 1500 to the red line.
https://youtu.be/NJ3RVOzIQ5g

1500 to 4500 in that vid so 3000rpm

You are joking ?

You understand that many petrols pull from 1500 - 7500 or more - which would be 6000rpm so double yours

Am I missing the whoosh ?

But the rate of acceleration in the 1,500 rpm petrol is very weak whereas it’s not in the derv. The diesel is punching 1.5-4.5k in the scenario you showed (the twin turbo and quad turbo 550d/X550dM pull into the 5,500rpm range.)


You could say diesel goes 900rpm to 5,000 rpm so a 4,100 rpm range and the petrol 750-7,000rpm so a range of 6,250rpm Now the question is of both rev ranges how much is usable on the public roads in gears above 1st. Secondly of that entire range where are they punching like for like and if it’s much harder in the diesel then they opt for a longer drive ratio essentially throttling back performance if you like but suitable ranges for U.K. roads.

In my C63 I cannot legally hit max revs or even max power in anything but 1 & 2nd. In my 535d I could do it in 3 years so yes only 1 more gear 4th was around the 100+mph. Fortunately for me I’ve got a lot of torque from my motor from very low revs but that’s not the case for the very vast majority of petrol cars - diesel on the other hand yep.

We’ve an S Max 140tdi and a family of 5. Our friends have the new shape S max family of 4 and a 140bhp petrol. We were following each other on a drive to stay in a rented house (holiday). Anyway motorway clearly speed limit no difference.
Up hills A and B roads - within speed limits he simply couldn’t keep up/despite using all the revs & they admitted having the car over 4K revs to 6k revs really wasn’t fun “buzzy” I think the word used. Instead I was 2-4K rpm in the stick shifting diesel.

So more weight same power add in hills no change.

[Fastdruid]

Welshbeef said:

But the rate of acceleration in the 1,500 rpm petrol is very weak whereas it’s not in the derv. The diesel is punching 1.5-4.5k in the scenario you showed (the twin turbo and quad turbo 550d/X550dM pull into the 5,500rpm range.)

Speak for yours. Mine makes peak torque from 1500rpm.

Welshbeef said:

You could say diesel goes 900rpm to 5,000 rpm so a 4,100 rpm range

Uh no. Just about every single diesel I've driven has been a gutless turd at 900rpm.

Welshbeef said:

We’ve an S Max 140tdi and a family of 5. Our friends have the new shape S max family of 4 and a 140bhp petrol. We were following each other on a drive to stay in a rented house (holiday). Anyway motorway clearly speed limit no difference.
Up hills A and B roads - within speed limits he simply couldn’t keep up/despite using all the revs & they admitted having the car over 4K revs to 6k revs really wasn’t fun “buzzy” I think the word used. Instead I was 2-4K rpm in the stick shifting diesel.

So more weight same power add in hills no change.

Apples with oranges try against someone in an SMax 2.5T and see how well you can keep up.

[nomis36]

V8RX7 said:

1500 to 4500 in that vid so 3000rpm

You are joking ?

You understand that many petrols pull from 1500 - 7500 or more - which would be 6000rpm so double yours

Am I missing the whoosh ?

I think what I should have said was relatively. I assumed people were saying diesels had a lot of punch for about a thousand rpm which some do but not all. Don’t get me wrong, I bought this car when my E36 M3 got stolen as a stop gap to getting another M3. So, I am a big fan of petrols but it has to be said, the instant shove of the diesel is very satisfying. My video I hope shows that not all diesels are sluggish noisy things, around 12 seconds to 100 and 5.5 to 60 is not slow especially considering it’s 14 years old and over 150,000 miles. I’m not pushing diesel over petrol because I like both. As for the “you didn’t red line it”......no maybe I didn’t but it will hit the limiter hard if I didn’t have some mechanical sympathy.

[Welshbeef]

Fastdruid said:

Apples with oranges try against someone in an SMax 2.5T and see how well you can keep up.

So you shouldn’t compare the exact same car with the exact same max power but one is turbo petrol the other is turbo diesel

You like to compare a 240bhp petrol Smax vs a 140bhp diesel?
Why not compare the top of the range diesel against the petrol so that’s 220bhp v 240bhp, naturally the 240bhp should win (don’t know if it does or doesn’t)

[Fastdruid]

Welshbeef said:

Fastdruid said:

Apples with oranges try against someone in an SMax 2.5T and see how well you can keep up.

So you shouldn’t compare the exact same car with the exact same max power but one is turbo petrol the other is turbo diesel

You like to compare a 240bhp petrol Smax vs a 140bhp diesel?
Why not compare the top of the range diesel against the petrol so that’s 220bhp v 240bhp, naturally the 240bhp should win (don’t know if it does or doesn’t)

The TDCI140 and the 2.5T make the same torque no? So exactly the same kind of comparison.

You've picked equal _power_ because it suits you. So why not pick equal torque instead and see where that gets you?

[Welshbeef]

Fastdruid said:

The TDCI140 and the 2.5T make the same torque no? So exactly the same kind of comparison.

You've picked equal _power_ because it suits you. So why not pick equal torque instead and see where that gets you?

No I didn’t “pick it” it’s simply one car we have and the other car is friends of ours and we happened To be driving in convoy - interesting given the same power output.

Not sure I’ve ever considered cloning up cars with the same max torque in which case you might see a bus against a Veyron.

[Fastdruid]

Welshbeef said:

Fastdruid said:

The TDCI140 and the 2.5T make the same torque no? So exactly the same kind of comparison.

You've picked equal _power_ because it suits you. So why not pick equal torque instead and see where that gets you?

No I didn’t “pick it” it’s simply one car we have and the other car is friends of ours and we happened To be driving in convoy - interesting given the same power output.

Not sure I’ve ever considered cloning up cars with the same max torque in which case you might see a bus against a Veyron.

You picked it to compare though.

If your friend had one that left you for dead would you have brought it up?

[fido]

Turbo petrols are a better match for diesels but they still lack grunt / throttle response at the low-end due to a lower compression ratio and less efficient combustion that diesels. Electrically-assisted hybrid turbos that fill in at low revs and new combustion technologies (Mazda SPCCI and Ferrrari/Maserati's pre-combustion tech) will make diesels even less attractive.