Torque VS Horsepower or Torque AND Horsepower?
Tue, 07/04/2009 - 05:15
So the answer to this question is perhaps longer than can be placed here, but I've always wondered how horsepower and torque play together. What got me thinking is that I noticed the new Bonneville has 67 ponies and that's only 7 down from the old and fantastic Guzzi 1100 I used to have. I would have thought the Guzzi pulled greatly more than the Bonnie and maybe it does when you factor in torque(Bonnie has 51 ft-lb of torque whereas Guzzi has 70 lb·ft)? Maybe these bikes are actually closer than I would have imagined. Indeed, I would have thought the Bonnie would have struggled a bit 2-up with luggage but my old Guzzi was fairly effortless at 80mph 2-up even. I'm going to try and get a ride on a Bonnie but I figure too that the Guzzis less effort is due also to torque numbers? I probably don't understand this relationship properly either :)
Tue, 07/04/2009 - 10:05
#2
BP
A good way to think of
BP
A good way to think of this is as follows (This is how it was explained to me a long time ago and it's stuck):
Take a man lifting a 10Kg weight up, say, 10 steps. Say also that he can carry it up to the top in 10 seconds.
Now, say he can carry 20Kg up the same steps in the same amount of time. He exerts twice the torque (But still the same power).
If he carries the 10Kg up the stairs in half the original time (5 Sec) then he makes twice the power but still the same torque.
So, torque is the size of punch/power he can exert. Power is how fast that punch/power can be exerted.
The torque curve is the other big factor here. The Bonneville engine has a remarkably flat curve (Something like 90% of the torque is available from 2500 Rpm upwards). As for the Guzzi, I don't know the figures however having ridden a V11 Sport some years back I'd say it had plenty of torque across the board. In short you'd have to ride the Triumph however I'd say that 2-up at higher speeds one will notice the lack of grunt on occasion. Whether the shortfall (I ride a 2008-model Bonneville America so I have experience here) will be an issue for you only you can tell.
Hope this helps.
Tue, 07/04/2009 - 14:49
#3
To be honest I think
To be honest I think separating torque from power makes things more obscure, not clearer. Mathematically they're directly related: power = torque x revs, but for some reason we talk about power when it's high revs and torque when it's low revs - a torquey engine really means it has good power at low revs.
The constant you're after by the way is 5454: if you draw torque and power curves on the same graph (and use bhp, rpm and lb.ft), they should always cross at 5454rpm. If they don't, the graph is wrong. Oh, and it should always be lb.ft, not ft/lb or anything else. The . means multiplied by, which is what you're doing, and ft.lb is a measure of linear work. Mathematically lb.ft and ft.lb are the same, it's just engineering convention to have them that way around.
It's all complicated enormously by a bike's gearing. The Triumph could easily have less torque than the Guzzi but feel stronger because it has lower gearing to compensate - we always discuss engine torque when what really matters is rear wheel torque. There, and you thought it wasn't obscure enough already...
The important thing with engine torque anyway, which you've talked about, is how the power - or the torque - is spread across the rev range. The Triumph has lots of it at low revs so it feels strong, although so does the Guzzi.
In practice there's not that much which you can tell from torque or power figures, although the curves tell you more, but something useful to note is that when the torque peak is at much lower revs than the power, this means the torque is decreasing as the revs rise. That means if you're cruising along at revs which are higher than the torque peak, if something like a headwind or slope slows the bike down, the torque actually increases as you slow, which makes a bike feel very strong. This is well known in the truck world as it's important with heavy loads when a truck comes to a hill - they call it torque back-up.
The bottom line is though, there are so many variables (we haven't even mentioned weight or power-to-weight ratio yet) that you can tell almost nothing from the peak torque and power figures and only a little more from the curves. The seat of your pants is much better... and the seat of mine says the Guzzi is a much better bet for loaded two-up riding than the Bonneville, it's a lot stronger at low revs.
Tue, 07/04/2009 - 15:26
#4
Wow. Shuggie, Navy, and Ash,
Wow. Shuggie, Navy, and Ash, extremely great info and very informative responses. Thanks so much to everyone. Very interesting read and I'm obviously not even close to being a gearhead. I've always had difficulty understanding these two things and even with the fantastic elaboration here, there are still some things I don't quite understand but I am getting there I think and the posts here have greatly helped. I am a librarian and I've done some searching online on this topic, but honestly, the posts here go further than anything I have found to explain this relationship. In terms of the Bonnie/Guzzi thing, as Kev notes, I guess seat of the pants matters more than just about anything and I'm going to get a ride, 2-up even, on a Bonnie this week. Even some owners who love love love their Bonnie's, and I think the white '09s are maybe the most beautiful bikes out there, have said "Fantastic bike, love it, but 2 up with luggage over long miles might strain you a bit" whereas virtually every Guzzi 1100 owner I know will tell you, "2-up, 75mph? Not even trying the engine much". But we'll see. Of course, lots and lots of other factors to consider between these two bikes other than horsepower/torque, but that's what I wanted to address here as it greatly surprised me that the little Bonnie turns out 67, but as you guys note, it seems tough gain much insight from a simple horsepower figure.
Sat, 17/07/2010 - 13:27
#5
Re: Torque VS Horsepower or Torque AND Horsepower?
Ostensibly Torque is a machines driving force. Power is a product of Torque. I think of a boxing sportsman, as an analogy, when thinking about Power and Torque:- Torque is how hard the boxer can punch. And Power, is how fast that he can repeat those punches.
In motorcycling terms, there are many dependencies and variables, from vehicle weight, aerodynamics, gearing, transmission losses, tyre compound and pressures, to fuel maps and even electrical system efficiencies. The list is practically endless in it's subjectivity, for those who are obsessed with minutia.
But, in basic terms to produce more power the engine must repeat it's punches faster (rev higher). To lay down that power the engine needs to rev freely, which can only be done taking into affect all of, and more besides, the caveats listed above.
People often say that twins have more torque. For the same capacity this is only true over a single. To produce more torque you need more capacity. To produce more horsepower you need revs and one easy way of doing this is to add more cylinders. So a thou four will produce more power than a thou twin. Fact.
So why do twins 'feel' more torquey? Well they are often lighter than fours (twin heads, but fewer pistons and rods etc), usually thinner (aerodynamics) and the big one - they don't rev as high. Which means, that the available torque is 'more accessible', which is why big capacity twins feel particularly good on the road, where they are harder to max out. Even this is not clear cut though, as twins will usually rev slower than fours, and so although fours are working harder, they are revving cleaner.
But for most people, most of the time, on the road, they would prefer the feeling of a 1200 v-twin at 6k revs than say a thou four at the same revs. There's arguments that slow pulses of twins (revving slower) aids traction, over a four, but I'm unconvinced.
I think that maybe people just find it easier to access the power and a bike always feel great when cornering and especially on exit when it's really under the proper meat of it's power, which is much harder to do on main roads with a 190 bhp inline four without twatting oneself.
Anyone who has ridden the new Multistrada 1200 for instance, will know that on their first ride, there were probably one or two corners that came up just a tad too quickly on them, as the speed seemed a little deceptive/relaxed, assuming they'd just stepped off an inline four.
One noble reason Triumph are selling more bikes in the UK than anyone else right now, exchange rates aside, is that everyone loves their triples when used on the road at real life speeds. The cliche of some of the torque of a twin and some of the top end of a four, are genuinely apparent in Hinkleys triples. The power (torque) is very accessible, and yet when the mood takes, the top end is usually not left too wanting either. Couple with a whistly characterful engine that is eager to rev and both the 675 and 1050 engines in particular make a lot of sense on the roads.
Generalising greatly: those that love to hear an engine scream, and live for trackdays, will benefit the most from an inline four. Those that whose mantra is he who gets there last still gets there and lives for easy almost lazy delivery will love twins. And those that can't make their minds up the triples will appease. Capacity is a personal thing, based on wallets and practicality of an individuals use. Broadly speaking the larger the better.
Personally I like large capacity over-square v-twin engines and triples. I'm a realist, don't do track days anymore and find these balance the need for speed or chilled out cruising on proper roads just right.
But with so many variable dependencies and personal preference considerations, the 'seat of the pant's personal test is the best advise you'll get; and we haven't even covered whether the colour schemes make your heart flutter or not! ;-D
Sun, 13/03/2011 - 20:46
#6
Re: Torque VS Horsepower or Torque AND Horsepower?
HP Torque and Work
When talking about the relationship between HP and torque I find it easier to first understand the term "work".
Maybe the following might be helpful.
Work
Work involves change. If nothing has changed then no work has been done.
Change takes time.
HP
Horsepower is a measurement of work. Work involves both change and time. Horsepower is the amount of work being done.
To measure HP, work must have been done.
Torque
Torque is a moment of force. It is a measurement of the force applied. It does not involve time.
So you can have torque without horsepower if nothing has changed, but you cannot have horsepower without torque (force).
Example:
If you apply torque to an already tightened nut and the nut does not move then no work has been done (the position of that nut did not change). But you have applied a force or torque. As a result, you cannot calculate the amount of HP applied because no work has been done, but you can measure the torque applied.
Only if you move that nut have you done work. Moving that nut took both time and force. If you know the torque applied to move that nut (ft lbs) and the time (RPM) that the nut was moving you can calculate the horsepower required to move that silly nut.
Summary:
It all comes down to work and how fast you want that work done.
If you want the work done twice as fast as before you will need at least twice the HP.
The force that is actually moving the bike down the road we call torque.
How fast (time) the engine can supply that torque (RPM) we call HP.
The faster the engine is supplying that torque, the more HP the engine is making because more work is being done or being done faster.
So, an engine supply 50 ft/lbs of torque at 10,000 RPM makes twice the HP (at 10,000 RPM) of another engine at 5000 RPM at the same 50 ft/lbs of torque.
In regards to rate of acceleration, it depends on the amount of reserve HP the engine can deliver to the rear wheel at that RPM.
Example:
Vmax 1700
700 lbs wet
200 lb rider
900 lbs total weight
3400 RPM in 5th @ 60 MPH
Suppose it takes about 12 RWHP to move the Vmax at 60 MPH on a level road at that constant speed in top gear. To have a good acceleration rate the bike in 5th gear would need to have in reserve (maximum RWHP at 3400 RPM)of about 65 RWHP available at 3400 RPM at 60 MPH.
That's why vehicles accelerate better in lower gears than top gear.
Sun, 13/03/2011 - 21:13
#7
Re: Torque VS Horsepower or Torque AND Horsepower?
ENGINE DISPLACEMENT & HP
Engine displacement alone is a poor indicator of maximum engine horse power.
Horse power output is dependent on two basic factors.
1 Total piston area
2 Compression Pressure
NOTE: Not displacement. Displacement is just the result of bore and stroke.
The basic limiting factors of maximum HP are:
1 Piston speed - until recently the upper safe limit at maximum HP was 4000 feet per minute on production bikes.
2 Bore to stroke ratio - until recently the practical limit was 1.5 to 1.
3 Compression ratio - the upper limit about 13 to 1.
4 Volumetric efficiency (how well it breathes)
5 Valve actuation system
6 Detonation
When considering maximum HP it may be more helpful to consider bore and stroke as separate entities rather then combining them together as displacement.
To date only the Honda Goldwing 1800 and the VMAX 1700 have the greatest total piston area of any production motorcycle at 40 square inches.
Of course the obvious question is if both have the same total piston area why does the VMAX 1700 develop 170 RWHP and the Honda Goldwing only about 105 RWHP. That will have to wait for another article.
The Triumph Rocket III has a total piston area of 37.7 square inches.
The Horex VR6 total piston area is 33.75 square inches.
The Honda VFR 1200 F V4 has 32 square inches of total piston area.
Engine stroke acts like a torque multiplier. The longer the stroke, the greater the mechanical advantage. In other words the longer the stroke, the farther the lower piston rod center is from the center of the crankshaft.
In a naturally aspirated engine a nice stroke length that would allow reasonably high engine speeds but favourable lower engine cruising speeds and torque would be around 64 to 68mm.
The stroke on the BMW K 1600 is 71 mm. It is limited by the engine design (inline 6 length) and their focus on good low engine RPM torque.
Stroke of the Honda 1800 Goldwing has the same 71 mm stroke. An engine with good low RPM power.
The stroke on the VMAX 1700 was not changed from the old VMAX and remains at 66 mm.
The stroke of the Horex VR6 is 55 mm.
Of course the addition of a mechanically driven variable speed turbo charger such as used in the Horex VR6 would allow the engineers to achieve almost any required torque, even at low RPM, to compensate for the short 55 mm stroke.
Sun, 13/03/2011 - 21:50
#8
Re: Torque VS Horsepower or Torque AND Horsepower?
I'm learning lots here, thanks.
One thing I don't understand is...
My 1100 Guzzi pulls a heavy Russian chair and hardly notices it, even with a passenger it just cruises along at 80mph so presumably has lots of torque, but you have to use the gearbox properly. It doesn't like to lug even as a solo and asks yout to change down the box into the correct gear even at reasonable speeds - unlike my old XJ900 which revs much faster and has less torque but you can leave it in top and lug the engine at slow speeds. Why?
My V strom is another big twin of almost the same capacity as the Guzzi but is quite different. You have to rev that at low speeds, it will stall at embarrasing times if you try to 'lug it'. How does torque/hp affect this? Is this - compared to the Guzzi's unstallable engine - down to the flywheel? I've noticed that vehicles I've owned & thought of as having loads of torque have had big heavy flywheels and those with low torque/high hp have light flywheels. Is this related - if so how?
Sun, 13/03/2011 - 23:50
#9
Re: Torque VS Horsepower or Torque AND Horsepower?
It doesn't like to lug even as a solo and asks yout to change down the box into the correct gear even at reasonable speeds - unlike my old XJ900 which revs much faster and has less torque but you can leave it in top and lug the engine at slow speeds. Why?
In a word: gearing. It's worth taking a look at the K1600 torque feature on here, linked from the home page at the moment, as it shows that while people compare engine torque, it's rear wheel torque that matters. The K1300 engine makes a lot less torque than the K1600 engine, but because the 1300 is geared a lot lower, its torque at the rear wheel - which is the only torque that matters - is much closer to the 1600's. That's partly because the shorter gear ratios amplify the torque more, and partly because at any given road speed the 1300 is revving higher and therefore making more engine torque. Then throw in the 1600's additional weight and you find the smaller, less torquey 1300 pulls harder than the 1600 at certain road speeds.
Your XJ900 will certainly be lower geared than the Guzzi because it's a higher revving engine, so while it might have less engine torque, it will likely have as much or more rear wheel torque. What's important here is that power is unaffected by gearing, but torque changes in proportion to the gear ratios - if a bike's rear wheel is turning at a quarter of the crankshaft speed, then frictional losses aside, it will be making four times as much torque.
The additional factor affecting lugging - loading the engine at low revs - is the flywheel. The Guzzi delivers its torque in one big lump per engine rev, and those are unevenly spaced too, where the XJ delivers two smaller lumps per rev at even intervals. The Guzzi's crank therefore wants to slow down and speed up much more than the Yamaha's, which you feel as lurching and general unhappiness through the transmission. A big flywheel smooths out that lumpiness, but it also slows down the throttle response.
Mon, 14/03/2011 - 00:40
#10
Re: Torque VS Horsepower or Torque AND Horsepower?
Thanks for responding "unconventional rebel".
You have brought up many intersting points.
Thanks for your explainations "kevash". You beat me to it.
This is my 2 cents worth.
Please remember the RWHP required to maintain a constant speed on a level road is much less (a fraction really) than the power required to accelerate or go up a hill or ride into a strong head wind.
Your 1100 Guzzi with a side car and passenger cruising well at 80 MPH is doing a very good job. You should be pleased.
The V strom also has a very good reputation. The differences in driveability may have more to due with their tuning characteristics and power characteristics than the flywheels.
Regarding low torque/high hp and light flywheels. I assume you are refering to over square engines of multiple cylinders that have high RPM HP ratings.
Flywheels don't make new energy (HP or torque). Flywheels absorb and store energy and release energy. The stored energy is released back into the vehicle which gives a momentary increase of torque to the driveline as it slows down if engaged to the driveline.
A single cylinder four stroke engine only makes power in only one of the four strokes. During the other three strokes the engine is actually slowing down. The flywheel absorbs energy during the power stroke and releases this energy during the other three strokes to help keep it running at low engine speeds and smooth out the power stroke pulses. So, generally a single cylinder engine or even a two cylinder engine often needs a heavier flywheel, especially if it is not a high reving engine like H-D V2 with a long stroke.
As the flywheel absorbs energy as the engine speeds up, the engine's RPM acceleration rate will be less depending on the flywheel's weight and RPM.
So, high reving engines of multiple cylinders (4 cylinder)
have many more smaller power pulses per revolution than a 1 or 2 cylinder lower maximum RPM engine. As a result they do not require heavy flywheels generally.
One area you might find interesting is the use of very high speed (60,000 RPM) compact flywheels developed by Torotrak. It is a re-generative system. Instead a flywheels being connected to the engine, it is connected to a Torotrak transmission and the braking system. When you apply the brakes you also engage a flywheel. The energy used to stop the vehicle is re-directed and used to accelerate the flywheel. Then when you accelerate, the energy from the flywheel goes back into the driveline to help improve acceleration and MPG.
In regards to low engine RPM performance/acceleration, I like to compare published top gear roll on acceleration times from 60 mph to 80 mph.
That way you are comparing apples to apples.
Generally, times under 3 seconds from 60 to 80 mph in top gear would be considered very good. The Vmax 1700 had a time of 2.66 seconds. The Suzuki B King 1300 was even a little better at 2.5 seconds.
Times from 3 to 3.8 seconds would be considered good. I think the Honda VFR 1200 falls in this area at about 3.6 to 3.8 seconds if I remember correctly.
To understand your bikes you would have to know the total weight (with side car) including the rider and the maximum RWHP at that RPM of the bikes at 60 MPH and at 80 MPH.
Power to weight ratios (total weight including the rider) at 60 MPH in top gear with good acceleration rates are usually between 15 lbs per RWHP and 18 lbs per RWHP.
So a 450 lb bike with a 200 lb rider would need about 43 RWHP in top gear at 60 MPH to achieve a power to weight ratio of 15 lbs per RWHP. This should give a roll on acceleration in top gear between 60 to 80 MPH of about 3.5 to 3.8 seconds.
The Vmax 1700 with a 200 lb rider is about 13 lbs per RWHP at 60 MPH in 5th gear.
Please correct me if I am wrong but I think a full sized H-D touring bike comes in at about 25 lbs per RWHP in top gear at 60 MPH.
I hope that helped a little.
Regards
Mon, 14/03/2011 - 22:59
#11
Re: Torque VS Horsepower or Torque AND Horsepower?
Thanks for the replies, I feel like I'm emerging from a fog into the mist, things are getting clearer now. The relationship of gears and torque is a good insight, as is a better understanding of flywheel function.
My favorite bike engine characteristics were on an XJR1300, a lovely engine for my style of riding, and I also am a fan of the V Strom lump now. Both engines I've read are 'detuned' versions of other engines, or perhapse 'retuned' for better mid-range at the expense of a top end I'd rarely ever use anyway?
How does this fit with the HP/torque debate? I understood the former was reduced and the latter increased? Apart from top gear roll on tests are there other things I should look for in my next bike in this area?
Tue, 15/03/2011 - 01:05
#12
Re: Torque VS Horsepower or Torque AND Horsepower?
Hello again "unconventional rebel"
In regards to HP/torque, high maximum HP outputs numbers always gets lots of attention and are always impressive. What many like, including myself, is good lower or mid range RPM power characteristics. We like lots of low RPM engine "grunt" in high gear.
If you like good low end and mid range performance maybe bikes like the Triumph 1050 or 675 or new 800 triple which still have still good maximum HP and very nice flat torque curves would be interesting. Acceleration from 60 to 80 MPH is about 3.3 seconds in high gear for the 1050 which is not bad.
By the mention of the bikes you mentioned it appears you like seem to fall in this catagory of good low or mid-range RPM performance.
Do you like naked bikes or bikes with fairings? That would be the next consideration I would think about.
How much money can you afford to spend?
Now we are going to go from the "objective" to the "subjective".
Numbers are fun to play with and can help with the "objective" part of selection but "subjective" involves emotions and peceptions. Difficult to measure.
In the end, the bike that is right for you is very personal.
The right bike will help you get into that moment when what's happening right now, and what you are feeling right now makes sense and you feel complete.
When you start it up in the morning does it make you feel good?
When it's parked in the driveway after she's all clean and polished, do you want to just sit down and look at her?
After a long ride when you are far from home and you are all alone with just that bike, and she starts right up after your rest and then takes you safely home, how do you feel?
Does that bike pleasently surprise you sometimes taking that special curve or hill?
Finally, is the bike there when you need it and does it do what you want when you want to do it?
If it does all that then it's probably the right one for you.
I picked up a little 1984 Honda 250 Rebel a few years ago. On a good day it might make 15 HP. To tell you the truth though, at speeds under 50 MPH I like it better than the larger bike I have. It idles so nicely and pulls well even from just above idle. It's a great bike for just plucking along a quiet back country road and just enjoying the view.
Sometimes simplier is better.
Regard,
JAG
Mon, 11/04/2011 - 14:48
#13
Re: Torque VS Horsepower or Torque AND Horsepower?
Kev, where would the graphs cross on my old big block Corvette then? It would never rev to 5454 rpm!
The figures it did have were 504 bhp @ 4400 rpm and 552 lbs. torque @ 3800 rpm.
Wonder where the graph lines would cross!
Mon, 18/04/2011 - 19:26
#14
Re: Torque VS Horsepower or Torque AND Horsepower?
They won't! They'll head that way but then they'll stop in an expensive mess and the sound of pistons hitting valves...
When I say 'always cross' that is assuming the lines get that far...
Sun, 03/07/2011 - 16:52
#15
Re: Torque VS Horsepower or Torque AND Horsepower?
A phrase I've always liked:
"If you want more torque at your rear wheel, change gear, if you want more power, change engine"
Torque can be ignored. Power is what matters, and the way it is spread through the range. Power determines the rate at which you are flung at the horizon.
Sun, 03/07/2011 - 21:58
#16
Re: Torque VS Horsepower or Torque AND Horsepower?
Torque can be ignored? Hmmm.
I take just as much interest in cars as bikes and i was thinking of 2 of my recent cars.
One had 237 bhp and 145 ft-lbs
The other 237 bhp and 229 ft-lbs
The second car, heavier, always felt like it had a bigger engine in it whilst the former, even though lighter, felt as gutless as hell. The only way to get anywhere was to scream it the whole time.
Sun, 03/07/2011 - 22:23
#17
Re: Torque VS Horsepower or Torque AND Horsepower?
Example:
If you apply torque to an already tightened nut and the nut does not move then no work has been done (the position of that nut did not change). But you have applied a force or torque. As a result, you cannot calculate the amount of HP applied because no work has been done, but you can measure the torque applied.
Only if you move that nut have you done work.
I am completely non-technical but the above seems contradictory in the extreme. If you apply torque to a nut as you just begin tightening it, very little energy is expended and therefore the amount of 'work' done (by the person wielding the spanner) is negligible.
A nut that cannot be tightened any more might have a very significant amount of energy (work?) expended in attempts to tighten. An extreme example might be that you harness 6 horses to the spanner and get them to haul with all their might - surely you are getting six horsepower worth of 'work' even if there is no visible result?
Mon, 04/07/2011 - 04:34
#18
Re: Torque VS Horsepower or Torque AND Horsepower?
Another point of view to consider about HP & acceleration
The basic problem is understanding what work is.
For work to have been done with the nut something must change/move. If nothing has changed then no work has been done on that nut.
Only if the nut moves has there been a change.
Whatever torque you have applied to that unmoveable nut was wasted energy.
Acceleration & G forces
I am wondering if there is another simplier way to relate to acceleration. We have spent a lot of time and effort trying to calculate how well a motorcycle can accelerate under different conditions. We calculate things like available RWHP or the amount of torque the rear wheel is transmitting to the road.
These calculations can be difficult. Accurate data to use in these calculations is often difficult to find.
What are we really trying to do? Why are we interested?
Acceleration or the feeling of acceleration is usually enjoyable in motorcycling.
What I think we are trying to do is describe a subjective feeling with objective measurements. Difficult at best.
Is there a point where the rate of acceleration becomes uncomfortable or unsafe?
Another unit we can use to describe the rate of acceleration is with G force calculations. There are G force calculators on line. All that is needed is the speed at the beginning, speed and the end and the time taken.
One advantage of using G force units to describe acceleration is that it may be easier for us to relate to the feeling of acceleration with other things we are familiar with.
1 G force of acceleration would feel as if your weight has doubled. If you weigh 160 lbs, 1 G force of acceleration would feel like you now weigh 320 lbs.
0.343 G force of acceleration would feel as if your weight has increased by about 1/3.
Examples:
1984 V65 Honda Sabre V4 1100 0 to 60 MPH = 3.04 seconds = 0.9 G force (average)
Ducati Diavel 0 to 62 MPH = 2.6 seconds = 1.087 G force (average)
VMAX 1700 60 to 80 MPH in 5th gear = 2.66 seconds = 0.343 G force (average)
VMAX 1700 0 to 100 MPH = 5.9 seconds = 0.773 G force (average)
VMAX 1700 0 to 60 MPH = 2.7 seconds = 1.013 G force (average)
Space Shuttle at takeoff = 3.0 G force
Roller Coaster maximum acceleration for brief periods of time 3 to 4 G force
F1 race car at startup 1.7 G force
Food for thought
Regards
JAG
Mon, 04/07/2011 - 11:44
#19
Re: Torque VS Horsepower or Torque AND Horsepower?
G force and acceleration
Another example many can relate to is a commercial jet aircraft on takeoff which average about 0.2 to 0.4 G force.
Based on these few examples it appears acceleration rates between 0.3 to 0.8 we would consider enjoyable in motorcycling. Above 0.8 to about 1.0 as still enjoyable but becoming difficult to hold on.
At some point the rate of acceleration may be limited to the available rear wheel traction and wheel spin. Loss of traction could be considered as unsafe since it means loss of control. Wheel spin is also wasted energy resulting in a decrease in acceleration.
You can also use G force calculations to measure decelleration such as during braking.
Bye Bye
JAG
Mon, 04/07/2011 - 13:51
#20
Re: Torque VS Horsepower or Torque AND Horsepower?
JAG - where did you get the 0-62 figures from for the Diavel? It seems like such a ridiculously short period of time, with it being a low target velocity that it would be easier to get more reliable times say 0 to 120mph.
I know on my Diavel that if I gun it off the line I barely have enough time to start screaming f..........! before leaving 62 mph way behind.
Mon, 04/07/2011 - 15:26
#21
Re: Torque VS Horsepower or Torque AND Horsepower?
2.6 seconds for 0-60 sounds about right for a Diavel, although it will have been achieved on a good surface with the tyre slightly under-inflated in all likelihood.
On longer acceleration runs as just mentioned, my Kawasaki ZX14T was timed at 0-150 in 9.5 seconds and 100 in 5.4.
It was an absolute beast IF you got the launch right and potentially fatal if you got it very wrong!
Back to torque, i feel certain that the 184 ft-lbs it had was a huge advantage in everyday riding, over an engine with the same power and maybe 130 ft-lbs.
Mon, 04/07/2011 - 15:28
#22
Re: Torque VS Horsepower or Torque AND Horsepower?
As an aside, can anyone here imagine 0-125 mph in ONE second.
In a piston-engined vehicle with pushrods and not even OHC!
Mon, 04/07/2011 - 23:44
#23
Re: Torque VS Horsepower or Torque AND Horsepower?
Now we can have some fun! 0 - 125 in 1 sec!
0 - 125 MPH in 1 second works out to 5.698 G force.
Fighter pilots without proper protection blank out at about 8.0 G force.
If you weight is about 180 lbs it could feel like you weigh about 1025 pounds. Hope you can hang on.
It had better be good because you probably couldn't do it a second time!
In regards to the Ducati, I got the 0 - 62 MPH time from Mr. Ash's road test I think.
As a side note:
I suspect the feeling of acceleration would be affected by the biker's riding position. A rider sitting vertically would feel the affects of acceleration much more than a rider in a racing position.
Could it be that the classic American cruiser rider position with the feet extended tolerates the poor HP of these big V twins because the feelings of acceleration, even if the rate of acceleration is poor, is more pronounced in that position?
H-D 60 to 80 MPH in top gear = 7.5 seconds = 0.121 G force (average)
Fun WOW!
JAG
Tue, 05/07/2011 - 00:07
#24
Re: Torque VS Horsepower or Torque AND Horsepower?
Hi
As kev says, gearing can make a big difference to acceleration.
A more subtle point is that the shape of the torque curve effects how strong an engine feels. For example if you have a motor which develops max torque at a low rpm, and you are traveling along with it spinning faster than max torque, then when you come across something like a hill, revs drop slightly and torque increases, giving you a feel of an unstoppable motor (the reverse happens to high revving engines, as speed drops, torque drops and you slow down more, meaning you have to reach for another gear)
Ps jet engines have bugger all torque but at 100,000 rpm will produce a pant filling amount of power.
Tue, 05/07/2011 - 00:13
#25
Re: Torque VS Horsepower or Torque AND Horsepower?
I am completely non-technical but the above seems contradictory in the extreme. If you apply torque to a nut as you just begin tightening it, very little energy is expended and therefore the amount of 'work' done (by the person wielding the spanner) is negligible.
A nut that cannot be tightened any more might have a very significant amount of energy (work?) expended in attempts to tighten. An extreme example might be that you harness 6 horses to the spanner and get them to haul with all their might - surely you are getting six horsepower worth of 'work' even if there is no visible result?
If you are heaving at a motionless nut, then no work is being done turning the nut. However lots of work is being expended heating up your muscles, the air around you, swearing and scribbly scrabbling to get purchase. You get tired because of the work you are expending fruitlessly. To prove the point, hang a big weight on the stuck nut and it will just sit there at rest, no energy being expended.
Tue, 05/07/2011 - 01:13
#26
Re: Torque VS Horsepower or Torque AND Horsepower?
Hello Rols,
I like one of your previous statements:
"If you want more torque at your wheel, change gear, if you want more power, change engine".
It appears 749R's ZX14T is a pretty hot bike.
ZX14T 0 - 150 MPH = 9.5 seconds = 0.720 G force (average)
ZX14T 0 - 100 MPH = 5.4 seconds = 0.844 G force (average)
VMAX 1700 and Diavel riders had better stay well clear of Mr. 749R's Kawasaki.
It also appears " OH F************K takes about 2.7 seconds to say during a 1.08 G force rate of acceleration.
Please note that my G force calculations are an average rate of acceleration during the time period. The peak G forces could be higher than the average.
Important questions:
What is a spanner? Could it be what we call a "wrench"?
What is a "tyre"?
Regards,
JAG
Tue, 05/07/2011 - 03:25
#27
Re: Torque VS Horsepower or Torque AND Horsepower?
Hello Rols again,
I have reviewed what I said in the previous statement when I stated:
" As a result, you cannot calculate the amount of HP applied because no work has been done, but you can measure the torque applied. "
I think I can see what you mean. I did not phrase it well.
Maybe what I should have said was:
" As a result, you cannot calculate the amount of HP required to move the nut because the nut did not in fact move. What you can measure is the torque or force or energy used or applied in trying to move it."
Thanks for pointing that out.
Regards,
JAG
Tue, 05/07/2011 - 07:44
#28
Re: Torque VS Horsepower or Torque AND Horsepower?
JAG.
The 0-125 mph is a Top Fuel drag car. I spent a lot of time around drag races in the early 2000s in USA and their cars (and bikes) were incredible devices.
0-340 in 5 seconds is what they do.
As far as my ZX14T goes (which i sold years ago btw), of COURSE it was in a different league to my current Diavel or a V Max! 250 bhp of turbocharged 1352cc, with 184 ft-lbs of torque ensured it was way quicker once it was under way. Initially, the Diavel would be quicker but by 80 mph it would reel it in and eat it for breakfast.
Geared up that same bike exceeded 200 mph with ease.
It was an extremely quick bike but remember that 0-150 in 9.5 seconds is way slower than many street-legal bikes.
Wed, 06/07/2011 - 02:53
#29
Re: Torque VS Horsepower or Torque AND Horsepower?
I am completely non-technical but the above seems contradictory in the extreme. If you apply torque to a nut as you just begin tightening it, very little energy is expended and therefore the amount of 'work' done (by the person wielding the spanner) is negligible.
A nut that cannot be tightened any more might have a very significant amount of energy (work?) expended in attempts to tighten. An extreme example might be that you harness 6 horses to the spanner and get them to haul with all their might - surely you are getting six horsepower worth of 'work' even if there is no visible result?
If you are heaving at a motionless nut, then no work is being done turning the nut. However lots of work is being expended heating up your muscles, the air around you, swearing and scribbly scrabbling to get purchase. You get tired because of the work you are expending fruitlessly. To prove the point, hang a big weight on the stuck nut and it will just sit there at rest, no energy being expended.
I bow to you techie guys but 'in old money' work is being done - it might be fruitless, but it is work. Is standing in the sea tossing bucketsful of water over your shoulder work? Just as pointless as the immovable nut-work but work nonetheless.
And if you hung that bag on a loose nut, and it turned, the only work being done is by gravity (who or what is expending energy?) - gravity is always at work - you don't always notice the effects of that work but it's happening 24/7
#amasconfusedasever
Wed, 06/07/2011 - 03:55
#30
Re: Torque VS Horsepower or Torque AND Horsepower?
If the nut turns, then the person who hung the weight there is the one who did the work. They lifted the weight. If the nut does not turn, then the energy remains unused as potential energy.
Tossing water over your shoulder is work too. You are heating the sea and air plus making sound. And looking a prat.
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Bragging rights - that what a lot of it comes down to, one could say in a cynical way, especially when it comes to power figures. Horse power is one of a number of power units that can be used but it is the one that we pretty much all know and love. However having now lived in mainland Europe for six years I am getting more used to hearing people talk about their engine in kilo watts. However that doesn't matter really - kw, hp or what ever you like.
If an engine makes say 100hp as advertised by the manufacturer, then that is a great figure to discuss with your friends but it is not the complete story as this peak power is made at only one place across the engine rev range. This is not necessarily at 100% full blat wide open throttle but lets assume that it is for arguments sake. So think about how often you ride with the throttle nailed to the stop? Not that often I would wager. So what it is interesting to us then really is how is the power of the engine delivered accross the rev range that we actually use. If the engine basically delivers next to nothing across the first three quarters of the rev range and moves like an arthritic donkey and then suddenly goes shooting off like a cat with a firework shoved up it's back passage, then it tends not lend itself to practical riding. So basically the published power figure is far from the whole story but it does tell you the peak power that engine is capable of putting out at a specific rate as power is also defined over a period of time in its definition. The original horse power was a definition of how heavy a weight an average horse could lift it per second/minute.
The torque is a component of, if you like but definitley not the same as the power. It can be thought of as the amount of effort that the engine is giving to try and turn the wheel. You have quoted ft/lb figures for the two bikes which again are a maximum figure as an engine does not deliver it all instantly right across the full rev range. However the units themselves explain it pretty well - 51 ft lb, is like having a wrench attached to a nut and that wrench is 1 foot long and if you hang a 51lb weight on the end of it, then that is how much torque you are applying to that nut (the Bonnie) your old Guzzi was capable of hanging a much heavier weight of 70lb on that same wrench. So transfer that to your back wheel what does it mean? It basically boils down to the fact that the Guzzi is applying more of its capability to turning the wheel and that in turn will feel like it is moving away a whole lot easier. You feel it as that widely known scientific unit called ooomph. Of course the ideal situation for you and your desire to cruise two up at 80mph would mean that which ever bike you buy the engine has a nice kind of flat torque delivery where it can accelerate through the gears effortlessly to get to where you want but still be sitting with enough torque for you to squeeze out of trouble should you need to. It would also be nice if the power curve of the bike was similarly in a nice position where at eighty mph you are using a good bit of the power and thus not stressing the engine but yet there is a little in reserve for the same emergency and you don't need to dance on the gear lever to find the correct engine speed to get it to shift.
There is a relationship between horsepower and torque in that the torque multiplied by the given engine speed divide by a constant, whose value I can't rememeber right now) will give you the hp figure at that engine speed.
In real world what does it mean though? You can feel torque through your rear end on the seat with that oomph factor but the actual power is harder to define in those terms.
I rekon that the Bonnie will still cruise quite happily with the two of you in the conditions you want but you will just experience a little bit less ooomph in getting there than you did with the Guzzi.
Sorry this is long winded but I enjoyed trying to answer. Also it looks better in writing mode than when posted as all the paragraphs and line breaks dissapear.