Is torque really relevant?
Discussion
Equus said:
RobM77 said:
Which model of 320d have you driven? My two E90s had pretty wide power bands for diesels.If you look at his posting history, his comments on almost every topic are extremely non-specific and look a lot like opinions that have been picked up by reading stuff on the internet.
Equus said:
RobM77 said:
I've found BMWs the most revvy by far.
I moved directly from AC43's favourite - a large petrol engine in the form of a 5.5 litre V8 Mercedes S-class - to a Jaguar 3.0 V6 diesel, and the delivery of the two engines is close enough not to be noticeably different in the real world.Certainly much closer than the big V8 petrol and a 'normal' (<2.0, 4 cylinder) petrol engine.
I think my lens gets a bit distorted by all the nasty manual 4 pot diesel hire cars I've had to endure on so many holidays.
Luckily, in the UK at least, they've been switching their fleets back to petrol for the smaller cars, anyway.
Although, because they're tiny capacity, that now means you now get turbo lag in them too...
'Powerband' (whatever people mean by that, as it could range in definition from the usable revs to the band of peak power), is relatively pointless comparator if the car has an automatic gearbox and sufficient ratios. A 320d will do similar speeds in similar gears to a 320i, the difference being the diesel has taller ratios, allowable by having greater torque.
The only practical differences are the amount of fuel they consume for any given horsepower (diesel wins here, as more efficient) and what they are like to drive (this will be down to personal preference). The petrol will be better for NVH at low rpm but this is offset by needing relatively high rpm to achieve peak power. The diesel will feel more effortless delivering peak power at low rpm, but the NVH will not be brilliant at low speed.
'Fun' is subjective, however there's an understandable theatre in using high revs and the aural pleasure that goes with it that petrols are great at delivering, whereas A road and motorway A to B journeys lend themselves better to low rev, high torque, in-gear behaviour, where diesels excel.
Torque is relevant only in so much as deciding whether you're happy with the power at lower revs (diesel) or higher revs (petrol).
The only practical differences are the amount of fuel they consume for any given horsepower (diesel wins here, as more efficient) and what they are like to drive (this will be down to personal preference). The petrol will be better for NVH at low rpm but this is offset by needing relatively high rpm to achieve peak power. The diesel will feel more effortless delivering peak power at low rpm, but the NVH will not be brilliant at low speed.
'Fun' is subjective, however there's an understandable theatre in using high revs and the aural pleasure that goes with it that petrols are great at delivering, whereas A road and motorway A to B journeys lend themselves better to low rev, high torque, in-gear behaviour, where diesels excel.
Torque is relevant only in so much as deciding whether you're happy with the power at lower revs (diesel) or higher revs (petrol).
ddom said:
If you had driven smaller engined modern diesel cars you’d be better placed to understand torque, and this topic.
Once again, you're making incorrect assumptions. Smallest (physically) diesel car I've driven was a Seat Ibiza FR (1.9TDI; manual... surprisingly good and flexible, particularly the in-gear acceleration in top on motorways).
I've also had a 1.4 TFSI Skoda Fabia vRS with DSG transmission (disappointingly gutless).
Still avoiding the question of your own experience, whilst incorrectly challenging everyone else's?
Equus said:
Damn right.
I'm having to tool round in a Citroen C3 courtesy car at the moment, 'cos my usual transport got caught in the garage by Covid.
f
king hateful little thing it is - 1.0 litre triple that you've got to thrash the nuts off and stir the gears on constantly to maintain any semblance of reasonable progress.
Bouncing off the rev limiter in stuff like a K-series Elise or Locaterfield is great fun in small doses, but when you need to do Norfolk to Exeter and back again in a day on a regular basis, it's absolute purgatory. Give me a nice, torquey diesel and a ZF 8-speed autobox, any day of the week.
This ! driving isnt for most of the time a racetrack or a competition, its 630 in the morning in the rain, with a meeting 200 miles away in a few hours, no between the hedges sunny august evening with the roof down. at lesat 90% of the population is seeing a car as a tool to do a task of conveyence.I'm having to tool round in a Citroen C3 courtesy car at the moment, 'cos my usual transport got caught in the garage by Covid.
f
king hateful little thing it is - 1.0 litre triple that you've got to thrash the nuts off and stir the gears on constantly to maintain any semblance of reasonable progress. Bouncing off the rev limiter in stuff like a K-series Elise or Locaterfield is great fun in small doses, but when you need to do Norfolk to Exeter and back again in a day on a regular basis, it's absolute purgatory. Give me a nice, torquey diesel and a ZF 8-speed autobox, any day of the week.
the debate about milage and petrol diesel economies ? it forgets the actual driver experiance. A petrol turbo low capacity engine its all about revs and being in the power band. its even been shown that those economy claims are pointless realworld as no one ever drives off boost... if ever an engine was designed around trumping the fuel economy tests then that was an engine to do it. I converted to diesel a few years ago now bar a couple of petrols but hands down diesel will always excel in driving.
an A6 with quattro, 5 seats 0-60 in 5ish and 155 top end, oh and mid forties and up on a run ? yup diesel six. thats the sweet spot until electric comes of age, and that wont be for a while.... electric wont until they can get a decent range and a short charge time. I have a car sat on the drive, it will do upwards of 500 miles on a tank, I could have arrived home parked up after a 400 mile run and 2 seconds later be out and going on another 500 mile run, yup ill need to recharge the fuel tank at some point but that would be a 500 mile charge in less than 5 minutes. That is what is holding electric cars back, if they could get a decent charge in a few minutes and the cost be comparable then we would not be using petrol or diesel cars.
back to the question, torque isnt relevant in its own right, however with other variables it forms the experiance. too low a torque and too heavy a car its a poor driving experiance, the torque curve not right you get a driving experiance that is woeful full torque off the line makes for snappy get aways but up in the rev range a low torque would make progress and overtaking hard work. this is something that electric motors suffer with high torque at low revs that fall as the revs increase. This is through how an electric motor works, Torque is a product of the amperage through a motor, and at zero revs there is no back emf being generated by the motor. so when you move off the line with an electric car it is pretty darn impressive. but as your revs increase the back emf from the motor increases and the current through the motor will drop. so the torque drops. They have done alot with motor drives to control this and provide the required torque control, however you got to see this in early electric vehicles as the torque did drop as speed rose.
Torque is important. but in the right aspect.
if it were me, Id be looking to have a good amount of torque and keep the relaxed driving experiance.
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!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.
(lower trace standard E92 M3)
(standard E92 320d)
Equus said:
Gary C said:
But slightly seriously, people do tend to thing cars with a turbo torque surge lower down do tend to feel the car is faster than when working an engine uptowards its rev limit, where actually, they are delivering similar torque to the hub...
But they're not.The peak torque to the hub may be the same, but the total through the range of revs as the car accelerates in gear (ie. the area under the curve if you plot a graph of the torque) is greater.
Just because one car has a flat torque curve, doesn't mean that the other car must have such a peaky output that its not delivering that torque over the range of the appropriate gear and thus be slower.
Thing is why are we talking about this, two main reasons spring to mind, driveability and performance, both interlinked, both more or less important, both have slightly different demands.
Two identical cars except for engine and gearing
Car A 500Nm peak
Car B 200Nm peak
Which has better drivability ? probably Car A
Which is faster, it is impossible to tell.
So refine it a bit more
Car A, 500Nm from 1500 to 4000 rpm (probably a diesel)
Car B, 300Nm 7000 to 8000 rpm (BDA ?
)Car A has a power of ~78 to 210 KW in that band
Car B has a power of ~220 to 250 kW in that band
So which is faster, again impossible to tell without knowing the gearing but if we assume Car A & B have ideal gearing for their respective engines, then Car B should be faster but you would have to work hard to keep it in the 6000 to 7000 rpm range and outside that range, often such an engine would drop off dramatically, making its drivability 'poor' (or nice depending how you look at it). It might even be 'slower' 0-60 if the gear changes take so much time, but 'faster' on a track once off the line.
Torque is what accelerates a car (actually the force generated at the tyre periphery as pointed out, but hub torque is simpler to use) but using the crank figure ignores the gearing
at 30mph, both cars in an ideal gear A at about 1500 rpm, B at 7000 rpm,
Car A is using a ratio of about (given an overall diameter of wheel of about 635mm) 3.72:1
Car B is using a ratio of about 17.36:1 !!!!!
Both floor the throttle
Car A delivers 1860Nm to its hub
Car B delivers 5208Nm to its hub
Car B accelerates much faster, but runs into a gearchange almost instantly whereas car A can keep accelerating, car B looses a lot of torque at the hub on the next ratio change whereas car A is accelerating at the same rate (discounting wind etc)
Which is faster, maybe Car A because Car B's engine & gearing is a bit extreme just to push the example, but maybe on a track, Car B is often faster given the smaller range of speed changes.
In the real world, just make sure you know your engine characteristics and use it properly.
julian64 said:
Can we discuss all the people saying diesels have a narrow powerband? Because the opposite is my experience.
I've always personally felt that diesels have a narrow powerband. The current 3 litre V6 diesel I have redlines at 5000rpm, whereas the petrol V8 M3 I had redlined at 8400rpm.You don't get much flexibility for me with a diesel engine, but they do feel effortless to use which I find that suits a daily. I don't really want to have to rev the arse off an engine to get the performance...like you have to in the N/A M3 for example on my commute. Others will enjoy doing that though I'd imagine, but I want effortless in a daily.
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!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.
(lower trace standard E92 M3)
(standard E92 320d)
Equus said:
Once again, you're making incorrect assumptions.
Smallest (physically) diesel car I've driven was a Seat Ibiza FR (1.9TDI; manual... surprisingly good and flexible, particularly the in-gear acceleration in top on motorways).
I've also had a 1.4 TFSI Skoda Fabia vRS with DSG transmission (disappointingly gutless).
Still avoiding the question of your own experience, whilst incorrectly challenging everyone else's?
It’s not incorrect at all, all you have to do is look at any dyno plot of any modern diesel to answer the question. You’re just making things up to justify why you prefer something over another to be honest. I get you prefer an automatic diesel, which is fine. Smallest (physically) diesel car I've driven was a Seat Ibiza FR (1.9TDI; manual... surprisingly good and flexible, particularly the in-gear acceleration in top on motorways).
I've also had a 1.4 TFSI Skoda Fabia vRS with DSG transmission (disappointingly gutless).
Still avoiding the question of your own experience, whilst incorrectly challenging everyone else's?
cerb4.5lee said:
Yes and the E92 M3 isn't really torque light but it can feel it though for me. A nice torquey diesel(not a 320d though!) always feels gutsy and effortless, although perhaps in reality they aren't actually all that quick...but they do feel it though for me.
I think the issue with the M3 is that people expected a traditional V8 experience, which with the rev range of the S65 isn’t going to happen. The complaint that they are gutless down the bottom end is just not an issue. They’ll easily get dropped if in the wrong gear by all manner of things though. But, that’s a case of driving them to their strengths. Depends if you enjoy a wonderful noise and linear power, or if you just want the easiest thing to do a job. Quite why any enthusiastic driver would say the latter for pure enjoyment is a mystery. But, there are many reasons with a daily car. Glad I don’t have to compromise tbh. cerb4.5lee said:
Yes and the E92 M3 isn't really torque light but it can feel it though for me. A nice torquey diesel(not a 320d though!) always feels gutsy and effortless, although perhaps in reality they aren't actually all that quick...but they do feel it though for me.
I think people recalibrate against the top end - so an EP3 Civic Type-R and a Focus ST-170 had similar torque curves up to the point where the Honda shifts cam profile and the Ford runs out of revs, but it's the Civic people think is lacking at low revs.ddom said:
cerb4.5lee said:
Yes and the E92 M3 isn't really torque light but it can feel it though for me. A nice torquey diesel(not a 320d though!) always feels gutsy and effortless, although perhaps in reality they aren't actually all that quick...but they do feel it though for me.
I think the issue with the M3 is that people expected a traditional V8 experience, which with the rev range of the S65 isn’t going to happen. The complaint that they are gutless down the bottom end is just not an issue. They’ll easily get dropped if in the wrong gear by all manner of things though. But, that’s a case of driving them to their strengths. Depends if you enjoy a wonderful noise and linear power, or if you just want the easiest thing to do a job. Quite why any enthusiastic driver would say the latter for pure enjoyment is a mystery. But, there are many reasons with a daily car. Glad I don’t have to compromise tbh. For a car that I only use for enjoyment(my 370Z) I don't mind that it hasn't got much torque(although for a N/A engine it does feel quite torquey). I really just enjoy using the revs more in that and I'm happy to stretch it right out for pleasure.
Torque is not really relevant if you are after performance. It just depends on your driving style. If you want to be lazy and stay in one gear then yes the diesel torque will give you more acceleration. If you are happy to adapt your driving to suit the engine then it doesn't matter either way.
We have two cars, one with 300 lb ft of torque, one with 130 lb ft torque, guess which one is much much faster than the other one..
We have two cars, one with 300 lb ft of torque, one with 130 lb ft torque, guess which one is much much faster than the other one..
otolith said:
cerb4.5lee said:
Yes and the E92 M3 isn't really torque light but it can feel it though for me. A nice torquey diesel(not a 320d though!) always feels gutsy and effortless, although perhaps in reality they aren't actually all that quick...but they do feel it though for me.
I think people recalibrate against the top end - so an EP3 Civic Type-R and a Focus ST-170 had similar torque curves up to the point where the Honda shifts cam profile and the Ford runs out of revs, but it's the Civic people think is lacking at low revs.cerb4.5lee said:
I haven't driven an EP3 Type-R but my perception of it is that it would be lacking at low revs. As is being discussed in the thread though-you can drive around it if you really want to. It is the same with the M3, and if you are prepared to drop several cogs and keep the revs up it will soon get a move on.
Lacking compared to a turbocharged engine or a higher displacement engine producing similar power for sure, but not really lacking for a 2L normally aspirated engine. The exceptional (for a production NA engine) performance at high RPM provides a contrast that can make it feel like it's lacking though.LimSlip said:
cerb4.5lee said:
I haven't driven an EP3 Type-R but my perception of it is that it would be lacking at low revs. As is being discussed in the thread though-you can drive around it if you really want to. It is the same with the M3, and if you are prepared to drop several cogs and keep the revs up it will soon get a move on.
Lacking compared to a turbocharged engine or a higher displacement engine producing similar power for sure, but not really lacking for a 2L normally aspirated engine. The exceptional (for a production NA engine) performance at high RPM provides a contrast that can make it feel like it's lacking though.I once owned a 2.2 Prelude VTEC and a BMW 328 - the BMW was for when I just wanted to get somewhere the Prelude was for when I wanted a fun drive
This was a rare moment when a unusually good FWD car was more fun than a good RWD car
(although my supercharged MX5 was better but sometimes 2 seats aren't enough)
cerb4.5lee said:
otolith said:
cerb4.5lee said:
Yes and the E92 M3 isn't really torque light but it can feel it though for me. A nice torquey diesel(not a 320d though!) always feels gutsy and effortless, although perhaps in reality they aren't actually all that quick...but they do feel it though for me.
I think people recalibrate against the top end - so an EP3 Civic Type-R and a Focus ST-170 had similar torque curves up to the point where the Honda shifts cam profile and the Ford runs out of revs, but it's the Civic people think is lacking at low revs.otolith said:
Perceptions are interesting, though - the butt-dyno is unreliable!
(lower trace standard E92 M3)
(standard E92 320d)
The thing is look at the RPM of both cars not just the curve. (lower trace standard E92 M3)
(standard E92 320d)
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.
If of course e92 M3 owners are constantly over 3k rpms all the time then it’s different - but I doubt they are else Mr She’ll or Mr BP will see them so often that dagadaga 320d will be long at the end location
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