I meant earlier to remind people that James May adopts a bumbling persona for reasons of style, it should be taken with a grain of salt. He knows what torque is all right.
As for shearing a rusty old manifold stud, well, if you haven't done worse than that more than once my guess is you haven't attempted much with old machinery... He's probably in his thirties isn't he? He'll learn. We amateur enthusiast mechanics haven't got a hoary old pro looking over our shoulders and telling us to stop it all the time. We learn by tedious and sometimes bitter experience.
|
"James May adopts a bumbling persona for reasons of style"
One of the reasons I prefer him to Clarkson. May knows more than he lets on, while Clarkson pretends he knows more than he does... IMHO, of course.
|
|
|
|
Good to know that Jeff Daniels is still flourishing.
He certainly used to. He wrote a very informative and easily understood book on the Citroen SM several years ago.
Hawkeye
-----------------------------
Stranger in a strange land
|
Torque... how about
Power (bhp) = (Torque lb.ft x Angular Speed rpm) / 5252
Or rearrange for Torque = ...
|
|
|
|
Good to know that Jeff Daniels is still flourishing. He was once the technical editor of Autocar ...
And an actor by all accounts ;o)
www.imdb.com/name/nm0001099/
|
This is more the part for me...:-)
www.jackdaniels.com/
Jeff Daniels has been a very fine journalist for many, many years and, as already pointed out, has a style that makes often complex technical subjects interesting and fascinating.
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
Remember, torque costs lives....
Especially if you use too much at the wrong time....:-)
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
|
That's Careless Torque then Stuart :-))
|
>>That's Careless Torque then Stuart :-))>>
It was of me to miss it out of the sentence...:-(
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
|
|
|
Given that energy expended is force multiplied by distance, we can work out power by factoring in time.
10 joules of energy is equal to a force of 10 newtons acting over a distance of 1 meter.
For those wondering what this means, a force of 10 newtons equals 1 kg. Imagine that you are lifting 1kg bags of sugar up a distance of 1 meter, from the floor to a shelf in your larder say. Lifting these bags makes you feel hot and tired and so energy is expended (you need to eat more). Ingoring the energy effeciency of the body we can deduce that moving a greater weight upwards requires more energy (technically force and distance repectively).
using our interpretation of torque or rotation force we can deduce that in 1 rotation of a bar (or crank) using 10 newton meters of torque we have expended about 63 joules of energy. If we traced a circle of radius 1 meter around a point we would draw a line that was about 6.3 meters in length that makes a circle. Using a force of 10 newton meters for 1 rotation must be the equilivilant of moving 1 kg upwards by 6.3 meters. That works about to be 10 newtons mulitiplied by 6.3 meters, equaling 63 joules.
Everyone knows about the relationship between distance, time and speed. We are quite comfitable in the nation that at 60 MPH we travel 60 miles in an hour. The notion of power is just as simple as that of speed. Power measures the amount of joules we expened in a second, rather the amount of distance we cover in an hour. Our units of measurements for power are watts, not MPH as in speed. A power of 1 watt is the equivilant of producing 1 joule of energy per second, just like 1 MPH is the equivilant of traverling 1 mile in an hour.
In our above example where one revolution of a bar (crank) we produce 63 joules of energy. If we rotate the bar (or crank) with the same force (10 Newton meters) every second we will expend 63 joules of energy per second. In other words we are producing a power of 63 watts.
We have deduced that an engine produces 63 watts, if turning at 60 RPM will be applying a turning force of 10 Newton meters. A kilowatt is just 1000 watts so that is the engine produces 0.063KW
Cars produce horsepower, not watts you may be think. Watts and horsepower measure the same thing, like MPH and KPH are the same units of measurement. To get from watts to horsepower you multiply by 1.341. The engine about thus is producing 0.063*1.341 = 0.085 HP.
Car engines don't run at 60 RPM, don't produce less that a tenth of one HP and don't produce just 10 newton meters of force, but I hope that the above provideds some intuition of how a rotation force (however it is measured), time and RPM relate to the variable of power.
As an aside I am sick to death by people going on about the extra torque diesels offers over petrol engines. Why on earth can't they just say look at how much power there is at low RPM! - For overtaking ability, power matters rather that torque. However low RPM may improve refinement.
Thanks Mfarrow, of couse you are right. It is just confusing how some car mags write Lb/ft, whereas it should be Lb*ft. To everone sorry about long post, if there are glaring errors say so. I just think that for the less technical the internet needs more posts like this one rather than misinformed ramblings.
|
That looks pretty clear to me.
BTW isn't your conversion from KILOwatts to HP...
|
Right you are, got my answer wrong by a factor of 1000. And I think I am intellegent.
Torque means nothing without RPM
|
|
|
|
And what about BMEP? That's what I want to know.
"> For overtaking ability, power matters rather that torque.<" Of course, but they are related for a normally aspirated engine. I've never understood the torque/power relationship with forced induction engines.
Higher BMEP at lower revs = higher available power at lower revs = torque at lower revs = immediate overtaking ability, which suits the lazy driver/rider.
However, expert overtakerists understand the need for an engine that revs quickly to max power and a gearchange that drops the revs back down to max torque on the upshift. A wide rev range between max torque and max power = flexible engine and fewer gear changes, a narrow rev range between max torque and max power = more gear changes required.
I can recall riding a 350 Yamaha many years ago that could bumble along at 30ish in 6th, open the throttle and "bwaauuggghhh", change down .. and again .. and again ... and again ... ah, that's where the powerband is. Keep throttle WFO and change up as and when necessary. So the inital impression is poor overtaking ability, but a little work produces expert overtaking ability. The impetuousness of youth. Happy days, except for the encounters with ditches, trees etc.
|
|
350 Yamaha - not an RD by any chance ?
|
">350 Yamaha - not an RD by any chance ?<"
Of course!! It had suffered molestation from Stan Stephens ... Banzai!!
Ring, ding, ding.
|
|
Yep, a lot of the kids I left school with went to their Maker on the back of one of these - probably only a couple but it seemed like a lot at the time. I have now had a flash back to Paris in 1981 and a pillion ride on one of these piloted by a very drunken Frenchman in a dress.......Christ !
|
">I have now had a flash back to Paris in 1981 and a pillion ride on one of these piloted by a very drunken Frenchman in a dress.......Christ !<"
Christ was drunken Frenchman in a dress? Possibly, I suppose. Did you get an autograph?
|
|
No it was an expletive based on the sudden memory jolt.......but I suppose it could have been. Thinking about me and bikes I've always ignored the most torquey ones until the GS. The nearest I came to this was the temproary stewardship of a Honda CX500, now that wasn't quick but power was available in every gear, the bnext nearest was a Kawasaki GT750 - very flat power delivery accorss the gears. This GS is something else and will pull in all three bottom gears without effort. It almost feels like a modern TurboDiesel in its power banding. This is genuine torque. The only thing I don't like is the occaisonal torque reaction rom the shaft.
|
|
So, PU, the torque stuff is all very interesting, but I'm sure we would all much rather hear in detail about your 1981 encounter with the drunken cross-dressing French Christ-lookalike on a RD350LC. Where you perhaps dressed in the style of the New Romantics? Any photos available?
|
|
Don't go there, I've just confessed one of my darkest secrets to the world....
|
">Don't go there, I've just confessed one of my darkest secrets to the world....<"
Perhaps in the style of the younger Ricky Gervais?
panopticist.com/graphics/seona_dancing.gif
Warning, this image may offend those of a delicate disposition.
|
|
">350 Yamaha - not an RD by any chance ?<" Of course!! It had suffered molestation from Stan Stephens ... Banzai!! Ring, ding, ding.
Was that RD watercooled?? I had a new RD 350 in 1975 and I swear that it was a 5 speed....but time and memory takes its toll...Please help!!
VBR....................................................MD.
|
">Was that RD watercooled?? I had a new RD 350 in 1975 and I swear that it was a 5 speed....but time and memory takes its toll...Please help!!<"
My RD was an LC (Liquid Cooled). If I recall correctly, the earlier air-cooled RD350A was a 5-speed and the RD350B was a 6-speed .... or was it the other way round? ;-)
|
|
|
|
|
|
>>So the inital impression is poor overtaking ability, but a little work produces expert overtaking ability. >>
Exactly the same technique with a diesel engine..:-)
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
|
Mops Brow - and the early 16v engines which were all promises and no delivery (especially in the power dept).
|
|
|
">Exactly the same technique with a diesel engine..:-)<"
Ah, but it's the long overtakes that become problematic with the infernal compression engine ;-) Things have improved over the years, but I can recall driving diesels with a powerband approx 2k rpm wide. I've ridden 125 two strokes with wider powerbands. But yes, the easy overtaking ability of diesels becomes more attractive as the years go by.
|
|
Especially bi turbo diesels.........
|
|
|
Ah, but it's the long overtakes that become problematic with the infernal compression engine ;-)
absolutely correct........ the initial 'get up and go' if you're in the power band is impressive...........but........
i really don't like the 'run out of steam' and quickly grab the next gear..... which doesn't happen with a petrol because you can rev it a bit more usually
|
>>which doesn't happen with a petrol because you can rev it a bit more usually>>
But you've already reached the speed needed in a diesel during in-gear performance, so it's not as frustrating as it might appear.....
My offspring has a Focus Zetec 1.8 TDCI which is the proverbial s--t off a shovel when pushed and has a slightly superior performance than the 2.0-litre petrol model. Great fun.
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
>>which doesn't happen with a petrol because you can rev it a bit more usually>> But you've already reached the speed needed in a diesel during in-gear performance, so it's not as frustrating as it might appear..... i didn't explain myself very well.........what i meant was when you are now overtaking the longest lorry in the world, because the chap coming the other way has rounded the corner at an absolute warp factor 5 and you'd really like to get your manouver over and done with pronto
|
>>i didn't explain myself very well..>>
You've got yourself in a bit of a tight spot as well....:-)
- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
|
|
">But you've already reached the speed needed in a diesel during in-gear performance,<"
Yes, for the short overtake, but not for the longer overtake.
|
|
Forget edit buttons. Certain elements could do with a torque button.
|
Another rev versus torque thred. Found comment about experiance with diesels as a good thing worth while. I have driven a diesel for about 2k miles, a pretrol for about 35k miles and for overtaking it has to be the petrol every time. However this is because I have had 1 near miss with a diesel. What I like is the low rev pull of the diesel, however it lacks power. The petrol engine car I drive is the renault 1.2 of 1996 max torque 2.5k rpm and max power 5k rpm. I am very confident driving this petrol car and I don't notice the revs since it has no tachnometer. I would say diesel and petrol cars are both great if you know the characteristics of the individual engine. I swear blind with petrol but that maybe because I learnt on a high rev, low torque engine and in the main drive one. For the diesel (doblo 1.9L, 105HP) I find it is good for overtaking if in the right gear and offers power higher up the in rev band.
Both diesel and petrol cars offer aceleration from 0-60 in about 12-13 seconds. Safe overtaking in both requires you to not think about torque but the aceleration offered by the engine and how acessable the power is in everyday driving. With both cars I find I need to change up a gear to overtake.
My mistakes when it come to the diesel engine are thinking that a band of torque at low revs will provide power, for me this essential condition does not hold. As for the petrol engine I find myself just wanting more power, but then I know this engine inside out.
For those who complain about the engine running out of power too early in the rev band, I know what you mean. The doblo's maximum power is at 4K RPM. The secret to safe overtaking is power+familiarity.
-----------------------------------------------
Torque means nothing without RPM
|
Torque means nothing without RPM
Hmmm, take two similar cars:
A 2.0 petrol geared to 25mph / 1000rpm in top will be doing 2000rpm at 50mph, some 1500rpm short of it's torque peak (iro 150lb ft). Putting your foot down will result in a rather lethargic response.
A 2.0TD geared to 30mph / 1000rpm will be doing about 1650rpm at 50mph, just building up to it's torque peak at around 1800rpm (iro 250lb ft). Put your foot down and it will stomp away.
The petrol driver would have to change down to perhaps third gear, around 16mph/1000 to be doing 3000rpm at 50mph to acheive the same level of acceleration as the TD, OK third gear would take it to perhaps 100mph at 6000 rpm if the driver wished though the TD driver would already be in top gear and could accelerate quickly and smoothly all of the way up to the car's top speed without needing a change.
|
The trouble with using torque as a measure of how "tight" (not a very precisely defined engineering term) to do a nut is that it depends on the friction between the nut, bolt, and washer, not just the amount of stretch being applied to the bolt. That is why in really critical situations an angular movement is specified.
But anyone who shears off a small bolt by using a two foot spanner is an idiot. The danger with a torque wrench is that you lose all "feel" of what is happening, and just go blindly on tightening because the book says 50 foot pounds or whatever. Experience and a spanner of a length appropriate to the calibre of the nut will sense when to stop, and also realise when it is tightening up for the wrong reason, eg because the thread is binding.
|
Britain's best sports commentator, Martin Brundle, has a useful analogy to explain the difference between power (BHP) and Torque in non-technical, non-mathematical layman's terms :
"Torque is how hard an engine can punch, Power is how fast it can punch"
|
Is that really helpful?
So far as punches are concerned, the faster they are, the more they hurt, i.e. the harder they are.
I'm confused.
|
|
"Torque is cheap." - in a Bronx accent
|
Torque may equal the weight of the fist when thrown in martins example.
-----------------------------------------------
Torque means nothing without RPM
|
"So far as punches are concerned, the faster they are, the more they hurt, i.e. the harder they are."
Shall we try an experiment. I hit you as fast as I can (power) for 5 minutes and Mike Tyson (or any heavy weight boxer) hits you once. Which would you prefer and survive? I think one punch from a heavy weight boxer will "hurt" more.
|
I think one punch from a heavy weight boxer will"hurt" more.
tee hee rtj, my very thought.
|
Ah, good old chedd appears.
The overtake from 50mph is not a long overtake. A long overtake could be several (many) mimsers, caravan types, autofiends and HGVs, all travelling behind an elderly Fordson Major c/w muck spreader. The convoy proceeds at 26 mph on a NSL single carriageway. The expert overtakerist will evaluate the situation, the resultant risk assessment will indicate that maximum accel from 26mph to ***mph is required to ensure safe, efficient good progress. One gear and a wide powerband is the only answer.
Even my elderly Crapi had an effective range of 25 to ***mph in 3rd. S2000 VTECs must have a huge single gear speed range. I'm sure someone has posted that recent Kawahondayamukis can reach 70+ in first. Or was that 100+? Very silly.
|
|
Just read up on my 535d's torque. 413lb feet (whatever) 30 more than the equivelent M5, 95% of the torque is available at 1500rpm, at 2000 rpm all the engine's torque is available thanks to the second turbo kicking in. You need to drive it know how that feels - debates about long overtakes are a diversion, this is one seriously quick car, this car has never left me feeling insecure during an overtake, even the other morning on an uphill section of three laner when the driver of a new shape Vectra gsi thing floored his to stop me getting past.....totally awesome car. Wish it had the M5 howl though that would have blown the coffee from his cupholder.
|
">this is one seriously quick car,<"
I'm sure it's very nice Pug.
But more importantly, when will you expand upon your epic pillon ride with the dress-wearing LC-riding camembertist Messiah? Did you wear Spandau-type pantaloons and a dab of make-up? I think we should be told.
Back to the less important things. At what rpm does the 535 reach max bhp? Does the power curve dip sharply afterwards? All rather feeble compared to your escapades in the early 1980s of course.
|
So, in a car that produces 228lb/ft of torque at 1900rpm and 130bhp at 4000rpm, what is an expert overtaking strategy?
a. Starting the overtake at around 3000 revs and changing down when reaching 4000
b. Changing down to hit maximum torque at 1900 revs (sounds unlikely)
c. Giving up and making way for Pugugly's 535d?
Any advice gratefully received!
|
">changing down when reaching 4000<"
Yes! That's the spirit! More revs.
|
So, in a car that produces 228lb/ft of torque at 1900rpm and 130bhp at 4000rpm, what is an expert overtaking strategy?
Start the overtake at around 1,900 RPM for decent shove, and give yourself a good 2,000 RPM of useful extra work to play with without needing another gear (most diesels tail off sharply past 4,000 RPM and need a swift upshift).
With the revs much lower the engine won't pull effectively, and with the revs much higher you'll be needing another gear almost immediately which although OK, isn't the smoothest technique for a swift overtake.
|
272 bhp @ 4000 rpm according to the book.
Is this an interview under caution ?
|
So, is it all over by 4500?
">Is this an interview under caution?<" Only if your answers confirm my suspicions regarding your nefarious pantaloon-wearing past. I have this recurring image of the Newly-Romantic PU hurtling around the Arc de Triomphe on the back of a furiously-ridden LC.
|
|
Done some digging plus a phone call to the guy that accompanied me (who is a Rosbief ) it was in a town south of Paris called Montereau. I feel a trip on the bike coming on.
|
Done some digging plus a phone call to the guy that accompanied me (who is a Rosbief ) it was in a town south of Paris called Montereau. I feel a trip on the bike coming on.
Surely PU you were the Rosbief, he was the Frenchman?
|
|
We both are/were. The Frenchman was French.
|
We both are/were. The Frenchman was French.
Je ne comprehend pas!
The Frenchman was French so not a Rosbief, that is a French name for an Anglais, so you were the Rosbief unless of course you are French too PU?
|
|
Sorry panic in the light of this exposure to the backroom. We were deux garçon Anglais on holiday in France (Rosbief x deux) when we met un garcon Francais who was dressed dans la habillement. After the shock memory I telephoned mon ami Anglais who confirmed the detail of my moment de madness.
|
Ah, good old chedd appears.
Please dont patronise!
The overtake from 50mph is not a long overtake.
That is not the point I was making.
|
">Please dont patronise!<"
Not at all, I admire your tenacity in supporting a lost cause etc ;-)
">That is not the point I was making.<"
Ah, but it was the point that I was making!
|
OK for Mciky's sake to expand on my previous point:
A 2.0 petrol geared to 25mph / 1000rpm in top will be doing 2000rpm at 50mph, the driver would have to change down to perhaps third gear, around 16mph/1000 to be doing 3000rpm at 50mph to acheive the same level of acceleration as the TD, third gear would take him to perhaps 100mph at 6000 rpm before he had to change gear. A useful range of 50 mph in that gear.
A 2.0TD geared to 30mph / 1000rpm will be doing about 1650rpm at 50mph, if the driver puts his foot down and it will stomp away all of the way up to it's max speed of around 130mph. A useful range of around 80mph in that gear.
If you do the comparison at lower speeds and lower gears the result is similar.
2.0 petrol geared to 16mph / 1000rpm in third will be doing 2000rpm at 30mph, the driver would have to change down to second gear, around 10mph/1000 to be doing 3000rpm at 30mph to acheive the same level of acceleration as the TD, second gear would take him to perhaps 60mph at 6000 rpm before he had to change gear. A useful range of 30 mph in that gear.
A 2.0TD geared to 20mph / 1000rpm in third will be doing about 1500rpm at 30mph, if the driver puts his foot down it will stomp away, third gear would take him to at least 80mph at 4000 rpm before he had to change gear. A useful range of 50 mph in that gear.
|
A 2.0 petrol geared to 25mph / 1000rpm in top .................. A useful range of 50 mph in that gear. A 2.0TD geared to 30mph / 1000rpm ..................... A useful range of around 80mph in that gear.
My Focus handbook states speed ranges in top of 31-126 mph (i.e. a 95 mph range) for a 2.0 petrol and 46-123 mph (i.e. an 85 mph range) for a 1.8 TDCi which is the nearest equivalent to the 2.0 petrol. Where did you get your data from?
--
L\'escargot.
|
My Focus handbook states speed ranges in top of 31-126 mph (i.e. a 95 mph range) for a 2.0 petrol and 46-123 mph (i.e. an 85 mph range) for a 1.8 TDCi which is the nearest equivalent to the 2.0 petrol. Where did you get your data from? -- L\'escargot.
It is a matter of what is theoretically possible and what is effective in use, the 1.8 TDCi will stomp away at 46mph in top, although in theory the 2.0 might pull 26mph in top (1000rpm ish) though even at 46mph it will need a change down to fourth or even third to keep up with the TDCi so accordingly will need a change or two up again before it reaches its max speed.
|
It is a matter of what is theoretically possible and what is effective in use, the 1.8 TDCi will stomp away at 46mph in top, although in theory the 2.0 might pull 26mph in top (1000rpm ish) though even at 46mph it will need a change down to fourth or even third to keep up with the TDCi so accordingly will need a change or two up again before it reaches its max speed.
My Focus brochure states acceleration times for 0-62 mph and 31-62 mph of 9.3 and 9.6 seconds respectively for the 2.0 petrol and 10.7 and 9.5 seconds respectively for the 1.8 TDCi. You keep setting them up and I'll keep knocking them down! ;-)
--
L\'escargot.
|
My Focus brochure states acceleration times for 0-62 mph and 31-62 mph of 9.3 and 9.6 seconds respectively for the 2.0 petrol and 10.7 and 9.5 seconds respectively for the 1.8 TDCi. You keep setting them up and I'll keep knocking them down! ;-) -- L\'escargot.
You are missing the point, I am talking top gear flexibility so 0-60 is irrelevant as is 31-62 in fourth. However note that the TDCi is marginally faster 31-62 in fourth even though it is higher geared.
|
I'm pleased you said "marginally"!
But being marginally quicker 31-62 doesn't necessarily mean that the car has travelled a greater distance by that time it reaches that time from a standing start. And don't forget that I'm already in front by the time I reach 31 mph. And I don't think that that 0.1 second advantage 31-62 will have enabled you to get past me on a single carriageway road. A better parameter for comparison is the time for a standing start quarter mile , or whatever the equivalent metric distance is. My next quest is to find a reputable source for that information.
--
L\'escargot.
|
">
2.0 petrol geared to 16mph / 1000rpm in third will be doing 2000rpm at 30mph, the driver would have to change down to second gear, around 10mph/1000 to be doing 3000rpm at 30mph to acheive the same level of acceleration as the TD, second gear would take him to perhaps 60mph at 6000 rpm before he had to change gear. A useful range of 30 mph in that gear.
A 2.0TD geared to 20mph / 1000rpm in third will be doing about 1500rpm at 30mph, if the driver puts his foot down it will stomp away, third gear would take him to at least 80mph at 4000 rpm before he had to change gear. A useful range of 50 mph in that gear.
<"
Which TD and which petrol? I'll select the 2.0 petrol for you: Honda VTEC, so your petrol rev range needs adjusting somewhat.
|
|
>> My offspring has a Focus Zetec 1.8 TDCI ............. has a slightlysuperior performance than the 2.0-litre petrol model.
But noisy and smelly with it. I'll stick with my 2.0 petrol.
--
L\'escargot.
|
>>Britain's best sports commentator, Martin Brundle, has a useful analogy to explain the difference between power (BHP) and Torque in non-technical, non-mathematical layman's terms :
"Torque is how hard an engine can punch, Power is how fast it can punch">>
That is a reasonable analogy it a bit simplistic, a boxer max be able to hit hardest at one punch a minute, alternatively he could hit at two punches a minute or more though each individual punch would be less strong. Re an engine max torque revs are where each cycle of each cylinder produces it's max effort, where the punches are strongest so if max torque is at 2000rpm then yes of course more power will be produced at 4000rpm because there are twice as many cycles (punches) though it wont be twice the power because each cycle (punch) is not as strong.
|
"That is a reasonable analogy it a bit simplistic"
Yes, of course it's simplistic, that's the whole point.
It's very easy to 'explain' technical concepts to the non-technically minded in such a way that the only result is complete confusion. Technical people are generally very good at this.
It is much more difficult to distill an idea down to its fundamentals, and use a simple analogy which anyone can grasp. That's why Brundle's analogy is so useful.
|
|
|
|
|
|
|
Given that energy expended is force multiplied by distance, we can work out power by factoring in time. 10 joules of energy is equal to a force of 10 newtons acting over a distance of 1 meter.
METER??
|
|
|
|
|
|
