Tough Torque

by Simon Hargreaves

KTM’s 1290: why they call it PR ‘spin’

KTM test rider and ex-500cc GP racer Jeremy McWilliams says the new 1290 Super Duke is the torquiest bike he’s ridden. KTM claim it makes more at 2000rpm than the 990 Super Duke at peak (70 lb.ft). That’s a lot of big torque talk.

Torque is often wrongly thought of as a measure of engine performance at low rpm. Big V-twins have ‘lots of low-down torque’, and inline four sportsbikes ‘lots of top-end power’, as if the two are discrete and opposite. They are different, but not opposites...

KTM’s 1290: why they call it PR ‘spin’

KTM test rider and ex-500cc GP racer Jeremy McWilliams says the new 1290 Super Duke is the torquiest bike he’s ridden. KTM claim it makes more at 2000rpm than the 990 Super Duke at peak (70 lb.ft). That’s a lot of big torque talk.

Torque is often wrongly thought of as a measure of engine performance at low rpm. Big V-twins have ‘lots of low-down torque’, and inline four sportsbikes ‘lots of top-end power’, as if the two are discrete and opposite. They are different, but not opposites. Torque is the primary measurement; power is calculated from it. Think of it like this: torque is the size of an engine’s punch, power is how fast it can throw it. They’re not exclusive.

Torque is a force making an object turn around a centre, such as twirling a spanner, turning a door knob or, in our case, pistons and con-rods spinning a crank. When a dyno technician talks about torque, that’s what he means (unless he’s bolting down a cylinder head). In the UK 1 lb.ft (or 1.4 metric Newton-metres) is defined as one pound of force acting one foot from its pivot. At 2000rpm, the 1290 Super Duke’s crank will turn as if it had a one foot lever with 32 bags of sugar piled on the end.

But that’s a snapshot. Engine torque changes with revs, as per a curve on a dyno plot. Two things matter: the shape of the curve, and the quantity of torque. The shape (and where peak torque occurs) is influenced by fundamentals like the number of cylinders, their layout, the bore, stroke and cam timing. If you’re designing a new engine, these are the foundations for its character. KTM based the 1290 engine on the Adventure 1190, so the shape of its torque curve is likely to be similar.

But quantity of torque derives mainly from engine displacement: ‘ain’t no substitute for cubes, although volumetric efficiency (how well fuel and air get into and out of the combustion chambers) and thermodynamic efficiency (how well it burns it in between) also matter.

But even with the 1290 actually clearing 1301cc, it’s basically a bored-out, stroked 1190 which KTM say makes 106 lb.ft at 6500rpm (90 to 95 lb.ft on the dyno). The nearest comparable V-twin is the Panigale R, at 90 lb.ft. But it’s unlikely the 1290 makes 70 lb.ft at 2000rpm as per the 990 Super Duke at peak, because it’s so far off peak efficiency. We can’t prove it because we dyno test in fifth gear and anything under 3000rpm stalls at full throttle. But so will the bike on the road, so it’s a spurious claim.

Either way, if the 1290 is the torquiest bike McWilliams has ridden, you wonder how gutless Kenny Roberts’ 2005 Proton V5 MotoGP bike was. And Jezza might like to try Suzuki’s Hayabusa, BMW’s K1600, Kawasaki’s ZZR1400, Honda’s GL1800 Gold Wing. And especially Triumph’s 2.3 litre Rocket III.

Because now, at 150 lb.ft, you’re really torqueing.

pittsy
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Quote: ".......makes 106 lb.ft at 6500rpm (90 to 95 lb.ft on the dyno). ....."

Very interesting article and one hell of a motor.

Why does the engine torque figure suddenly change when you strap the bike to a dyno?

Let's give KTM the benefit of the doubt and say that the 106 lb.ft is true. Presumably if we measure directly at the crankshaft then this is the torque figure we will measure. But where can we measure the 90 to 95 lb.ft? Where does the 90 to 95 lb.ft actually exist?

Just a thought!

Cheers

Captain Scarlet
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You cannot measure torque at the crank, which is precisely where all manufacturers claim their claimed power outputs come from. Davide Tardozzi famously offered a million to anyone who could prove a crank measured power output.

You can strap things to the crank to get a reduced output figure and extrapolate back an estimate (probably accurate sometimes even) or you can offer RWHP which will typically lose 10-15% - dependent on running gear (final drive method, gear ratios, tyre choice and so forth. The figure will also alter depending on other factors such as the ambient temperature, the altitude and the calibration of the dyno too.

The only relatively accurate and fair figure to offer is the rear wheel output on a recognized international DIN rated dyno.

I've always maintained that it's a bit disingenuous IMPO of manufacturers not to quote weight figures with all fluids, including a full tank of fuel and power at the rear wheel figures only. They'd all have much better street creed with real riders if they themselves got real and told it like it really was.

I don't care how light my bike is when it's in an unrideable state and I don't care how power it's 'crank' output is, if that's not what hits the road every time I turn the throttle.

I think Jezza's comment may be taken out of context. Or rather Jezza worded it badly. I think what he actually means is the KTM has th best torque to weight ratio that he has experienced.

And Si is right in that torque is largely linear with capacity. And that there are more torque laden (of significantly heavier) bikes.

What isn't mentioned is that most people believe twins have more torque than fours, but the opposite is true for the same capacity bikes. What is felt is that the torque of a twin is making more power lower down the rev range. I.e. It's more accessible and this is why a Harley engine feels powerful at legal speeds, but then soon runs out of puff as in-line fours scream out passed it.

The other key thing of course, is that horsepower is based on torque, because it's torque that is the actual 'power'. Horsepower is just how frequently that power can be repeated. Hence strong torque gets a heavy motorcycle off the line quickly and horsepower keeps it's momentum going longer at speed.

Dyno charts are often confusing because imperial measures show torque and hp lines always crossing at 5,200 rpm and DIN metric one's crossing at 7,100 rpm I believe. If the lines cross anywhere else, treat with severe suspicion!

pittsy
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Hi cap'n. Hope you're well. It's Sunday at approx 6.45 am here and I'm out on the road shortly. Sun is shining after a poor Saturday of rain.

Extensive answer! Unfortunately I don't think it answered my two main questions. Ultimately one "bottom line" question.

Why does the crankshaft torque figure suddenly drop when you strap a bike to a rolling road dyno? My own opinion is that it doesn't.

Where does the 90 to 95 lb.ft figure exist? My own opinion is that it doesn't exist. It's an abstract interpretation.

I wish tarrdozzi had offered me the million squidly's. I'd have taken him up on it. I reckon I could hire a brake dyno, machine up suitable prop shafts and a jig, then pop the engine portion of my bmw flat twin in there and still have plenty of change out of a million. I could even hire it out to anyone with a guzzi, or an old Brit bike, or an old Harley......

But to engage with my questions we don't need to actually do the measurements. I'm ultimately talking about a principle. We can use faith and accept that the KTM figure of 106 lb.ft is true. I am quite prepared to accept it. What I want someone to answer is; when the crankshaft torque of 106 lb.ft happens, where exactly is the 90 to 95 lb.ft happening? Which shaft? (Answer = none, imo).

Simon proposed that the 106 lb.ft is real enough, until you strap the bike to a dyno (I assume rolling road). What mysteriously modifies the torque figure? (Answer = man. IMO)

The thick plottens.

Off for me ride now. Catch you L8R.

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A fascinating subject and relevant to us all. For me it's the curve of the torque curve that's of arguably greater importance.

The Triumph triple motors, especially the 1050 motor has a famously flat curve. That's what makes it so cracking to ride, for me at least.

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CS wrote: "The only relatively accurate and fair figure to offer is the rear wheel output on a recognized international DIN rated dyno."

That's fine, but my point is that I find it bemusing the way torque figures are basically abused where rolling road graphs are concerned. If you want a fair and accurate rear wheel output for torque, you'll need a graph for every gear. Sorry, but that's just the way torque behaves.

As you say, the transmission losses amount to between 10 and 15 percent and that's fine when you consider power. Power isn't multiplied by the the very same gears and chain ratios which are responsible for the power loss. But torque is multiplied by the reduction ratios (and also subject to the losses).

What most dyno graphs seem to show is rear wheel horsepower and also a curiously abstract torque curve derived by plotting rear wheel power against crankshaft speed.

This is, in effect, an abstract interpretation of crankshaft torque but with all the transmission losses removed. Trouble is, the crankshaft output won't have been subject to the transmission losses because they all occur downstream of it. So the actual crankshaft torque won't be the figure you'll see on a typical rolling road printout. Not as I see things anyway.

You could argue that it challenges the perception of what is fair and accurate.

Cheers

Navy Boy
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A wise man once said:

'Power figures sell bikes - Torque is what makes people enjoy riding them'.

Except if you're into your Harleys that is!

pittsy
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Let's not forget that the torque which really counts is at the rear wheel. In fact it's not even that. It's ultimately the force which pushes the machine. The force at the tyre to road contact. Wheel rolling diameter has a say in things.

I find those cutaway illustrations of something like a moped or small scooter fascinating. Looking at the ridiculously small piston and negligible stroke and marvelling at how on earth it manages to propel the vehicle. Even better is the same illustration of a 600 sportsbike. Again, puny pistons and stroke, able to propel the machine at 160 odd mph. Pull power wheelies in the lower gears.

Amazing.

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Quite right Pittsy.

I took my Triumph TT600 for a nice ride yesterday - It's amazing how such a small engine can propel the bike along like it does.

This issue also highlights, for me at least, a bigger issue for the bike industry in general. That is the way bikes are 'Profiled' and the sorts of qualities that the manufacturers seek to get from them. Honda's NC700/750 bikes have shown us all the sorts of fuel economy and running cost figures that can be achieved by aiming for real-world usable torque rather than chasing power figures.

The TT600 of mine is a classic example of this. Maximum torque made around the 10500 revs/min mark yet I rarely venture up there and even then only for a very short period of time. So the bike's hardly ever working at its theoretical point of maximum efficiency or its 'Biggest bang for your buck' point to put it more colloquially.

By way of contrast my Harley XR1200 made its peak torque at 3700 revs/min which equated to around 67-68 Mph in top gear. Far more usable and relevant for road riding and as such the Harley was better on fuel than the Triumph (Yes I know there are a number of factors to this but this is one of the bigger ones).

Don't get me wrong, the TT is great fun to ride but if powered two wheelers are going to convince non riders to start using them then fuel figures and associated running costs are going to have to start becoming more advantageous.

pittsy
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Hi navy boy.

It's certainly a fascinating topic. A perennial topic, as far as motorcyclists are concerned. Torque. Power. Which is better? Which is most important? Etc.

From a transmission engineers perspective power is king. Give me the power, regardless of the rpm (within reasonable limits connected with the topic) and you can have the torque. You'll just need a different ratio sir. You can have exactly the same torque from your 1200 cc twin at (say) 5000 rpm as you can from your 500cc four at (say) 14000 rpm. If you're not getting it, you're in the wrong gear!

Obviously it ain't quite that simple. Well, it is from the engineering formula's point of view, but not from ours as a rider, out on the road. We're a fickle lot anyway (I know I am!). One day we want big, fat, juicy torque at low rpm. The next we want torque rising with revs, onward and upward. It creates an exciting motorbike.

From an mpg point of view, going back to your mentioned 68mph. What sort of power does that need? Obviously it'll vary slightly, but most 125cc bikes will do that, near flat out. So about 12 to15hp? So is a 125cc on wot more economical than a Harley xr1200 on about 15 percent throttle? Has to be surely? I dunno. Food for thought though. Hee Hee.

Cheers.

Captain Scarlet
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"If you want a fair and accurate rear wheel output for torque, you'll need a graph for every gear. Sorry, but that's just the way torque behaves."
... dyno graphs are usually generated with bikes in fourth gear, so they are at least comparable. But actually, what you really need is thrust curves.

However, even these are subjective, as they will alter dependent on revs applied, and running at permanent maximum revs is not real world.

So, for example, A ThunderCat 600 will produce stronger thrust curves at 6,000 RPM than an R6, which makes it a better engine for road use, whereas if judged in 4th gear at max revs, the R6 will look impressive, and probably would be over the ThunderCat on a race track, because the top-end is being spanked as you would expect.

As always bikes that feel torquey (typically big V2's) may not produce the most torque (typically big inline 4/6's), but offer more 'accessible' torque. Typically 2-4th gears at half revs is where it's at 'punch' wise.

And at those revs, bikes like Harley's, Victory's, Indian's and Ducati's 'feel' powerful, even if they can't always repeat those power pulses as quickly as larger capacity bikes with additional cylinders when it comes to the higher revs. There's a reason why Harley only quote torque figures, and this is it.

Captain Scarlet
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"Unfortunately I don't think it answered my two main questions. Ultimately one "bottom line" question."
... I think it does. You're just not listening! ;-D

Power is lost throughout a moving drivetrain because of both friction and the amount of power it takes to physically move heavy components such as sprockets, chains, wheels and tires - and there's your 5% loss at the rear wheel (the other 5% is manufacturers over-inflated claims).

Manufacturers do actually bench test the power coming from the crank (which is different than the power it makes), which will be slightly less than the crank because of the reason I mention above. They then extrapolate this figure using an algorithm known only to Honda boffin metallurgists, to best 'guess' the actual crank figure. Kevin actually mentioned this himself about five years ago, when a similar debate was in the mix.

So why do manufacturers do that? Simple. Because they 'cannot' measure power at the crank as an exact figure... and Mista Tardozzi bet is safe. No wonder he's a Moto-GP big-wig now eh! ;-D

"What most dyno graphs seem to show is rear wheel horsepower"
... nearly true. Just to compound the voice of ambiguity in a sea of reason, the figure is still mildly extrapolated to account for the minuscule loses between tire and dyno roller. And don't get me started on the affects of chain versus belt versus shaft, and gearing, and lower unsprung weight, such as lighter tires... and stickier tires. Or ambient temperature. Or artificial air induction fans, used by some dyno shops. Or sea levels and ambient temperatures. Anybody that thinks getting EFI mapping should be a doddle when you have dependencies like that, before thinking about different power modes, power deliver, and world fuel differences in terms octane, purities and additives, probably hasn't thought it through properly - because I've thought of all these things and consider myself a complete novice on the subject!

"Obviously it ain't quite that simple."
... there it is - the voice of reason, in a sea of ambiguity :-D

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Hello captain!

CS: "... dyno graphs are usually generated with bikes in fourth gear, so they are at least comparable. But actually, what you really need is thrust curves."

Yes, the graph is generally produced in one gear, and therein lies one the compromises of the rolling road dyno, to my eyes at least. It's what they do to the graphs next, which is the crux of my original opening post point. I'm not rolling road dyno bashing by the way. I'm not in a position to do that. Even if I were, I don't want to. That's not my point at all. What I'm saying is that I (think I) know an abstract torque curve when I see one. And for that matter a very curious power curve too.

Because of the need to use (say) fourth gear and because of the way torque behaves when transmitted through a multiple reduction transmission, to try to give an actual rear wheel torque to go along with the actual rear wheel horsepower, would be, let's say awkward. Not awkward for the dyno. The dyno will know that information first, it needs some further number crunching first to get my abstract torque figure. Just "awkward". Slightly inconvenient.

What seems to happen next, with the majority of graphs I can find, is that they will then take the actual rear wheel power curve and plot a torque curve against it (back calculating, if you will) to generate a torque curve at crankshaft speed. Surely you can see the abstractness of that principle? By association it also makes the power curve odd. Because that too, although genuine in its value for power at the rear wheel, is at the wrong speed!

Can you not see what I'm getting at here? With power it's ok (the wrong speed against it isn't ok) we can say we put 100hp in at the crank-shaft and end up 85hp at the rear wheel-shaft. We've lost whatever along the way due to the reasons you gave. Fine. No problem. But what about our poor little torque curve? Oo er. That's not behaving the same way. The blighter has been multiplied by the reduction ratios. That's inconvenient of it, so we'll back calculate a torque curve at crankshaft speed. That leaves us with an actual rear wheel power value, a bogus rpm value and an abstract torque value. The torque value doesn't belong anywhere. See my point? Reason in a sea of ambiguity!

Tuners don't seem to give this a second thought, presumably because they know what they're looking at? It's definitely useful, as long as you know what you have. All the transmission losses have been pre removed. But it's not actual. It's abstract.

Any chance of anyone agreeing? Slightly? A weeny bit?

pittsy
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CS said. "Manufacturers do actually bench test the power coming from the crank (which is different than the power it makes), which will be slightly less than the crank because of the reason I mention above. "

Hi

I don't understand that paragraph. Did you mean to say "clutch basket" at some point there, or am I just not getting it? If so, please explain again! Ta very much.

Captain Scarlet
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"Can you not see what I'm getting at here? .. The torque value doesn't belong anywhere"
... not really, but then again I could be validly be accused of being slightly ignorant of such things, with only having very rudinentary mechanical engineering skills. I'm not sure about torque being an extrapolated figure, which seems to be what you're eluding to? In theory it would be the other way around, wouldn't it? I.e. HP is an extrapolated ('repeatability') product of the 'real' power, which is torque. That's what my spotty Bengal cat, Cougar, says anyway.

Did you mean to say "clutch basket"
... no. Kevin said something along the lines of the front sprocket output shaft, before it loses power from that point back to the rear contact point. But because it has to turn another object still (a female splined shaft of some kind I presume), and there is weight and friction associated with those metal objects, there will be some (but fewer) loses. And arguably it will be easier (closer at least) to extrapolate a figure closer to the actual reality of what the crank is making. I'm not clever enough to know how all that stuff works. I'd have to ask an learned metallurgist, or my Meeza cat, Hooch.

Anyway, my tabby cat, Vinnie. Wants to know what y'all (he's from the south doncha know), think about the new Indian Scout? Right, that's enough talk of pussy for one thread...

pittsy
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CS: ". I'm not sure about torque being an extrapolated figure, which seems to be what you're eluding to? In theory it would be the other way around, wouldn't it? "

Yes.

What I'm alluding to is better thought of as "back calculating". I'm suggesting that a lot more goes on within the computer of a rolling road than is generally spewed out on the ticket. Not always, though. I can find some "genuine" curves showing "actual" happenings, although by far the majority of rolling road dyno curves are essentially an abuse of the HP formula and, basically, a misrepresentation of facts.

Look at the rpm.

We get shown a genuine rear wheel "absorbed" power. But you won't generally see the genuine rear wheel rpm against it on the other graph axis. You'll see crankshaft rpm. So that leaves the resultant torque figure in a very abstract place. It's not crankshaft torque. It's not rear wheel torque. It's not a torque figure for any of the shafts involved. It's what it is! An abstract back calculation, using the wrong rpm.

The correct torque figure, to produce the power figure we see, is buried in the computer. We don't (generally) get shown that. It is substantially higher in value because it will have been multiplied by the gears and chain. The rpm is not correct. It is crankshaft rpm. Yet the power value we see is rear wheel.

Making any sense yet?

Cheers captain.

Edit: I won't change anything I've written above, but in retrospect I feel saying that the majority of rolling road dyno curves misrepresent facts is too strong. If it offends, I apologise. It gives the impression I'm against rolling roads in some way. An abuse of the HP formula? Well, yes, from one point of view. You can input whatever you like into the formula, but only the data which actually happened will give the right answer.

Captain Scarlet
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"by far the majority of rolling road dyno curves are essentially an abuse of the HP formula and, basically, a misrepresentation of facts ... It's not crankshaft torque. It's not rear wheel torque. It's not a torque figure for any of the shafts involved. It's what it is! An abstract back calculation, using the wrong rpm ... in retrospect I feel saying that the majority of rolling road dyno curves misrepresent facts is too strong."
... I agree and don't feel a misrepresentation of justice. Dyno curves are misleading for a multitude of varied dependencies. They are subtly manipulated to suit the data suppliers and ultimately derived from the extrapolations of smoke and mirror boffin-esque assumptions. The only linear constant is two machines tested on the same rig back to back. But even then, the data cannot be normalized completely, only brought more in line, by example: fitment of the same brand new tyre compounds and engines of the same mileage etc. This is why Si, and most other journo's have run many tests trying to eradicate as many variables as possible, to provide the most like-for-like comparisons for their readers, even if it is an almost impossible and totally discombobulating oxymoron of a task.

I think what I've said also holds true too. In terms of exactness, power cannot be measured at the crankshaft itself, and loses from source (crank) to product (contact patch) are intangibly apparent in a qualitative perspective as a direct result of the (again varied) reasons that I sited, which means any quantifiable metrics (we'll call them dyno figures for simplicities sake) are highly subjective at best. You know I once asked a mechanic if he knew roughly how tight to tighten a fastener or bolt if he didn't have a torque wrench handy. He told me there are only two measure... tight... and 'effing tight! I'd wager that the seat of the pants torque-ometer will tell anyone who test rides a bike, whether it is fast enough for them, or really 'effing fast enough for them - it could be 'all the data' they'll ever need! ;-D

pittsy
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G'day cap'n.

You know, I'm still feeling like we're at crossed purposes.

Even if, by some miracle, we could obtain absolutely perfect readings, it doesn't change my point. My point is not about accuracy (well, in an indirect way you might say it is), it's fundamental manipulation of a formula I suppose. The figure you'll commonly see given for torque is plotted against rear wheel power, but at crankshaft speed. The answer is abstract.

John Robinson described it as "effective crankshaft torque". I came up with the same description completely independently, before I read his book.

Effective, but not actual.

Makes yer think.

Captain Scarlet
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"we're at crossed purposes"
... only in the sense that you're failing to realize that you now agree with me that claimed crank power is effective/extrapolated and not 'actual' :-D

Johno was a very good man. And a very intelligent man. A bit like Kevin. Some pass this world too soon.

pittsy
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".. only in the sense that you're failing to realize that you now agree with me that claimed crank power is effective/extrapolated and not 'actual' ......"

So, going back to the OP and indeed simon's comment, you agree that the crankshaft torque doesn't actually drop from 106 lb.ft to 90/95 lb.ft, when strapped to a rolling road.

Excellent.

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Well I'm glad that's sorted then!

Navy Boy
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Well I'm glad that's sorted then!

pittsy
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"Well I'm glad that's sorted then!"

I doubt it!

Anyway, on a connected subject, the other night I watched a top gear from 2010. On it they ran a merc sls versus a Ferrari 458 through their speed traps at, I guess, a 1/4 mile.

Riddle me this. Both cars have identical max power outputs but vastly different max engine torque. They both ran virtually neck and neck all the way and crossed the traps with identical times.

Edit: forgot to say that the kerb weights are the same.

Captain Scarlet
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"I doubt it!"
... naturelmont my fickle friend :-D

"So, going back to the OP and indeed simon's comment, you agree that the crankshaft torque doesn't actually drop from 106 lb.ft to 90/95 lb.ft, when strapped to a rolling road."
... I don't recall saying it did or didn't? The (accurately unmeasurable) power at the crank doesn't change from whatever it is. But the power at either the sprocket or rear tire will noticeably - both based on the friction loses and the type of application/bike. A ten percentage difference between a manufacturers 'claimed' (extrapolated or whatever nomenclature) crank figure and a 'typical' dyno wheel is typical, as well we know. Well... some of us! ;-D

"merc sls versus a Ferrari 458"
... I had the pleasure of thrashing a C63 CMG (would like to try the SLS) around Brooklands and then the 458 Italia last year at Road Atlanta. I guess the similar weighted, powered and geared cars perform similarly? Okay, I'm being facetious ;-D The Italia has better aerodynamic, but the (black series at least) SLS puts out more power. I’m guessing that’s primarily why they’re similarly quick over the quarter. I wonder how the new Hellcat versions of the Dodge Charger and Challenger would fair in a straight line comparison. They’re heavy, but giving the man in the street 707 hp to play with is surely commendable! :-D

pittsy
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"... naturelmont my fickle friend :-D"

Hee Hee. Yes, I suppose I am. At least that. Sorry!

"... I don't recall saying it did or didn't?"

Well, by default. That's what I've been saying and you say we agree. Torque though, captain, is the main issue. Straightforward manipulation of the mechanical power formula. Not really extrapolation.

"I guess the similar weighted, powered and geared cars perform similarly?"

My point was meant to be regarding the vastly different engine torque figures not affecting the outcome (and suggesting the gearing is actually also very different).

Cheers captain.