I copied this from Motorcycle Consumer News...January

Thunder Star The First Sports Diesel



We have seen the introduction of a few new diesel powered motorcycles recently, but up to date all have been built to produce good torque and fuel economy, with "touring" style performance, but the Thunder Star 1200TDI is quite different.

Dutch company Star Twin Motors is a relatively small firm headed by engineer Kees van der Starre, well known for his advanced ideas on motorcycle and three wheeler design and responsible for the construction of previous small batches of exotic examples; like a 900cc single for racing. But now he has created a 1200cc turbo diesel with performance to match many sportbikes on the street and on the track, and with superior torque.

The engine is not a converted car unit, but built in house under the direction of engineer Jeroen Bernart, although it is true to say that a number of its internal components are sourced from both cars and motorcycles, all housed within Star Twin's own CAD/Cast casings. The development of the engine started almost four years ago, and has now reached a very sophisticated and efficient stage. The 1200cc liquid cooled, 3 cylinder, turbo charged diesel, is fitted with an inter-coole, has direct injection and a compression ratio of 16:1, and uses a five speed gearbox and a dry slipper clutch.

Currently, the output is 70hp with 118lb/ft of torque, but this is being increased in steps to test the effects of the considerable power on the components. By the end of the year it is estimated the bhp will up to 100 and torque 145-185lb/ft. The result of this is quite incredible acceleration in every gear, so much that the rider can easily mistake which ration he is actually using. Even so, they say a fuel consumption of 94 mpg is quite attainable.

Kees, in his original conception of the bike, while going for sports performance, realized that he must also address the weight problem often associated with large capacity diesels. So, having produced the engine unit, he then set out to produce a genuinely sporting rolling chassis of minimum weight. Thus, the frame is a tubular steel structure utilizing the engine as a stressed member, fitted with a ultra light WP brand GP forks and a mono shock. The wheels are carbon fiber (wrapped with 120/70 and 190/50 17 tires), as are the fairing and other small components, keeping the weight down. The front brakes are of PFM manufacture; twin 320mm discs with radially mounted six piston calipers, and a small Brembo twin piston unit at the rear gripping a wavy disc.

The result of this is a wet weight with 4.75 gals. of fuel and ready to roll of just 444 lbs.....right on the mark of similar capacity gasoline powered sports bikes. Add to that to the massive torque on tap and its easy to realize just how well this bike will perform.

Production is possible in small batches, (Girthy has dibs on the first one says Kees) and may eventually be farmed out to other companies with greater resource in this area, but for now Star Twin Motors have proven such a bike can be built, and really does perform.

Well, you know, if you lie to the dyno and "tell it" the 12 is turning only half the rpm it actually is, then the dyno will tell you it makes 180 ft/lb of torque!

And, the cut-in-half false rpm figures will still probably be faster than this engine is turning!

Not that the bike isn't cool -- it's just that most don't seem to realize that torque, as reported by the dyno, is actually nothing but a manipulation of the hp and does not report the force generated at the rear wheel: the more rpm the dyno is told, or it measures from the ignition, the more it reduces the measured hp to come up with a calculated torque. Kind of bullshit, and irrelevant to anything, as in fact there's no way that hp at higher rpm is not as good as hp at lower rpm.

No real reason to penalize it on account of higher rpm, which is what the dyno calculation does.

The measure of this thing's useful power is the hp figure or the hp curve, and while the curve isn't provided, the peak of 70 hp says it's weak, just a little bit above a Japanese home-market sports 400, but of course heavier than those. Nice job if he's able to get the rear-wheel SAE hp to say 120 though and a broad rev range though!

That is a good point,

another number that sticks out is 94 mpg :shock: :shock:

Yeah, that ain't bad!! :D

What I'd love is a diesel dirt bike. I just think that would be cool. Some company has made a KLR650 like that for the USMC, but I don't know if its in service yet. It definitely isn't available to the general public.

Slap a turbo on that and you'd have something... :wink:

sweeeeeet :wink: :wink:

BTW I like the frame, gas tank, seat, and tailpiece. Very nice work, completely primo.

It will probably sound very weird. 440 Miles on a tank would be fantastic though.

Maybe they should have used an existing bike to fit the engine to it, I think it will be quite expensive - producing in small batches and all.

Trenace, you have it backwards. A dyno measures torque, not HP. The way to determine HP is to multiply torque by rpm/5,252. The drum of a dyno measures the turning force(torque). Once you know the turning force at a particular RPM, then you use the formula to determine HP.

I thought that was the case, but I'm not smart enough to question anybody..... I'm too busy questioning myself.

Great sounding idea. But, does anyone know if a turbo deisel runs hot? Big motor right at your legs and tight underseat exhaust.

I'm inclined to think this thing will fry you nads in about 10 minutes.

Workman, you're incorrect in saying I had it backwards, with regard to dynos measuring at the rear wheel, which is what we generally are talking about.

Such a dyno measures the force at the rear wheel -- linear force, incidentally, which would be a direct measure of the twisting force at the rear wheel if diameter were reported to the computer which it isn't, but that's incidental.

It also at the same time measures the speed of the rear wheel, or really the speed of the drum. The combination gives horsepower.

The dyno doesn't ordinarily report the linear force at the rear wheel, and this force also is not the same as the rear-wheel torque -- the same rear wheel torque will yield different linear forces according to the diameter of the tire but at this point we're getting into finer details than necessary.

This force measurement the dyno makes of the rear wheel, is NOT the torque at the crankshaft. And the difference is not simply one of driving losses. Depending on what gear you're in and what gearing you have, and depending on what sprockets you have, the same crankshaft torque will yield vastly different rear wheel torques.

The dyno can't measure that.

So what it does is exactly as I said: it computes the hp based on the force measured at the rear wheel and the speed, and then it derives from this a calculated torque based on what rpm it thinks the crank is turning.

Unplug the ignition, and what you get is only a hp curve from the dyno, not a torque curve.

It's exactly what I said.

It can't compute torque at the crankshaft without using the ignition rpm information. Can't do it. It can and does measure hp just fine without that, and uses that computed hp as the next step in computing the crankshaft torque, if the engine rpm information is available.

If it were told the engine was spinning half as fast as it actually is, it would tell you twice as high a torque, or vice-versa.

Your specific statements are generally technically right -- other than claiming the dyno computes hp from the torque, if you meant crankshaft torque as we were talking about -- but not the overall conclusion, because what they prove is what the dyno measures directly is rear wheel driving force, not crankshaft torque, which as I've explained is an entirely different matter and is a product of both engine torque and gearing.

This results in the penalization -- from those giving importance to such figures -- of engines operating at higher rpm.

For example, suppose Engine A has a powerband from 3000 rpm to 12000 rpm and generates 90 ft lb of torque throughout.

Engine B generates 120 ft lb of torque throughout its powerband, but it's a slow revving engine and that powerband is from 1500 to 6000 rpm.

Which engine will have more rear wheel torque on the road?

Engine A, once you gear the engines to give identical or even similar speeds in gears.

Just a fact, Engine A will deliver more twisting force to the rear wheel in use. Fifty percent more, thanks to being able to gear it shorter due to its being a faster-spinning engine. It's the far more muscular engine throughout an equally wide rev band, regardless of the "torque" figure.

Fact is, people confuse rear wheel torque with crankshaft torque, and imagine that lower revving engines with high such torque are going to have more torque at the rear wheel. Not necessarily so and often not so, because the lower revving engine also has to be geared taller and this gearing proportionally reduces torque.

The torque figure reported by the dyno hides this, by "penalizing" for how high the ignition rpm is, and rewarding slow-turning engines. If it directly reported rear wheel torque that would not be the case.

That's why a stock 12 will easily outmuscle a Harley Davidson that has "more torque." At the rear wheel at any given road speed it does not, despite the dyno numbers, for the above reasons.

now you just know that BIG SAINT will be drooling when he sees a diesel powered sportbike! :D

When I said you had it backwards, I meant 'torque and HP'. It should be obvious to anyone that a dyno measures power at the rear wheel, not the crank. So for the purpose of this discussion, I mean power measured at the rear wheel.

You said,
This makes no sense. If you give me a HP curve, I can tell you exactly what the torque curve is and vise versa. The two are inextricably linked.
Without an ignition wire to measure engine speed, what is being measured is the torque at the rear wheel without consideration to gearing. By reading RPMs of the motor, and comparing it to the speed of the drum, it can determine gearing and convert the power numbers to coincide with the speed of the motor and not the speed of the wheel. Regardless, you cannot measure HP without first knowing torque. Even without the ignition wire attached, the dyno will accurately read torque, just that it will be the torque of the rear wheel at a given speed without taking into acount the gearing. Once you have this info, it is easy enough to convert it to coincide with the engine RPMs if you know the gearing of the bike.

There is tons of info out there about how dynos work and the relationship between torque and HP. I'll try and post a few links when I get home. But think of it this way: Horsepower is a measure of torque over time. Specifically, 550 foot-pounds of torque per second. A dyno most definitely measures torque. Once you know this, its just a matter of plugging in the formula to determine HP.

Sorry, Workman, you're wrong... it's exactly as I said.

You're incorrect as to how the reported torque value is computed.

If you unplug the ignition from the dyno -- or don't have it plugged in the first place -- what you get is a hp curve with no torque curve. Regardless if you're aware of that or not, or claim it makes no sense. It's simply fact. Happens all the time, every day.

This is because the dyno computes the crankshaft torque curve from the hp curve as I stated, rather than the other way around.

And, as I said, the faster the dyno thinks the crank is spinning, the greater the factor it divides the hp by to give its calculated torque value (which is not reported as rear wheel torque or drum torque but as what it is calculated to be at the crankshaft.)

You appearing to be trying to turn this into a conversation about drum torque, but no one was talking about drum torque, drum torque figures aren't reported, and furthermore, drum torque will be higher (at a given road speed) for a bike like the ZX-12R with a higher spinning motor than for a bike like a Harley with greater crankshaft torque but spinning slower, for reasons I stated, so everything I stated remains correct from that view as well.

Re-read my posts if you want to understand this, they are correct; while your claims that the reported torque values (which represent engine torque not drum torque) don't depend on input of engine rpm are incorrect -- they do.

This is unusual, BTW -- usually you're more knowledgeable on the technical stuff than me, but on this one you do have a misunderstanding of it.

Sorry Tenace, you are most definitely wrong about this. Plain and simple, HP is a measure of torque over time. Also, a dyno does not measure or convert the numbers to read crankshaft torque(or HP), it strictly measures rear wheel power and converts it to coincide with engine RPMs. The dyno report has nothing to do with crankshaft power and isn't meant to be interpreted that way. The report gives a power curve in relation to RPMs and with no consideration to power loss through the drivetrain.

Look it up.

Whatever... you don't get it. That you don't get it doesn't change a single fact though.

Continue believing what you wish.

But, if you have an open mind, try puzzling out to yourself why without the ignition plugged in (or another source of engine rpm info) the dyno will give you a hp curve no problem but will not give you a torque curve -- and you can't get the engine's torque curve without that input. Hmmm, why is that?

If the hp curve is derived from the torque curve, how is it that you can get the hp curve while the dyno operator tells you he can't give you the torque curve because the ignition isn't plugged in? Just how can this be if the hp curve supposedly comes from the torque curve or reported torque values? Well, I explained it for you.

Also try figuring out why you get the same (to very close approximation) reported torque values regardless of what gear you do the pull in or what sprockets you use, though of course rear wheel and drum torque changes greatly according to the gearing. The information I gave you, which you reject, explains that for you... but it will be a real puzzler for you if you continue to deny that it is as I've said.

Namely that the reported torque curve is a result of computation that divides by engine rpm -- the same measured values at the drum give lower reported torque if the dyno thinks the engine is spinning faster. Or even a higher measured value at the drum will give a lower reported torque value if the dyno thinks the engine is spinning much faster, as a result of this process. Higher spinning engines are penalized in their reported torque value, for same measured value at the rear wheel. But this has been explained before.

No need to answer... just stuff for you to think about, if you have an open mind, though all this is already explained above anyhow and you would not accept it then, so probably not now either, as a guess.

Don't take my word for it:

http://www.revsearch.com/dynamometer...orsepower.html

http://www.pumaracing.co.uk/power3.htm

http://www.sportrider.com/tech/146_0102_dyno/

You have a track record of posting links as proof, that don't remotely prove what you're claiming... please quote the parts that you claim disprove anything I said, versus what I actually said as shown by the "quote" feature; and while you're at it, see if you can answer the questions I gave you while continuing to reject what I said.

Let's see it. Or will you dive out...

Listen, you don't seem to understand -- based on your above posts -- the key fact that for dynos measuring at the rear wheel, the ignition input is needed to get the reported torque curve and torque values (while it isn't for hp.) I am sure that others here can confirm for you that it is as I've said, and your denial on that is wrong. The reported torque values are computed using engine rpm as a required input, and the faster the dyno thinks the engine is spinning, the lower the value it reports for torque from the same hp from the same measurement at the drum, as a result of dividing by engine rpm to yield these torque values. Precisely what I said, that you denied.

Why not start with that, since you're disputing something that's just a basic fact familiar to many.

http://auto.howstuffworks.com/horsepower2.htm

Every article listed states that dynos measure torque and calculate HP. Short of a declaration from Sir Isaac Newton himself, what does it take to prove this?

Girthy....dude....you can have that ugly ass thing man...lol....damn ...that just may be uglier than a Busa !!!

I wonder where the spark plugs go on that thing? 8)

Avenger, all you would hear Girthy do is spool the bitch up and all you would see is Black smoke.

It dont look purdy but it would be a blast to ride 8)

Funny how your first 3 links, supposedly disproving what I said, had nothing in them that you could quote that disproved anything I actually wrote (assuming you take the care to make the distinction between torque at the drum, which we are not talking about and is not a reported value, and the reported torque values which is what we are talking about, but perhaps you are not getting the distinction) -- instead you found another link.

Your new "How Stuff Works" link does have a statement that asserts differently. However, it still remains a fact that the dyno does not know, does not measure, cannot compute the figure that it reports as the torque.

Not without dividing out by the engine rpm, supplied by the ignition, precisely as I said.

Don't know who wrote that little article, but what they stated is not so for a dyno measuring at the rear wheel, at least not with "torque" referring to reported values (as opposed to drum values which aren't reported and the discussion was not about, and never on this forum has been about when talking about a bike's torque. Hell, show me one dynograph anywhere that gives the drum torque... I highly doubt you can, that is not the reported value, and would vary enormously according to gearing in any case.)

Measuring at the crank is another thing. But we weren't talking about such dynos: I was clear on that.

You've still failed to explain how it is -- if my statements that the reported torque values when using a rear wheel dyno are done by dividing by the engine rpm, generally off the ignition, are incorrect as you claim -- that the dyno can't provide the torque figure without that input from the ignition.

You've still failed to explain how it is -- if my statements are incorrect -- that the dyno reports essentially the same torque values regardless of which gear you use, say 5th or 6th, and regardless of your sprockets, although these of course greatly affect the torque at the drum.

It's simple -- go back and read what I wrote. You'll find much more substantive info there than in your brief "How it Works" link.

Here, I'll explain it to you a different way, maybe you'll get it then:

A dyno reports 100 hp under a given condition. Now, it can do this without being able to report the torque -- if you don't have the ignition plugged in, the engine rpm fed into the dyno, it isn't able to report the torque -- you are finally going to agree this is true, or come out and deny it? Yes or no? That's only in bold because I made a major point of it before, asked you to start with that, and instead you posted your "How it Works" link. So I feel I have to emphasize the question for any chance of an answer.

You tell me what torque figure the dyno should put on the chart and how it is obtained.

Can you do it? What do you need?

Answer, you can't do it without the engine rpm (or if you think you can please show how!) If I tell you the rpm is 5252 then the answer is 100 ft-lb. If I tell you the rpm is 10,504 then the answer becomes 50 ft-lb. If I tell you the rpm is 2626 then the answer becomes 200 ft-lb. Any of these could be the case at any drum speed, depending on the bike's gearing, which the dyno does not employ in its calculations nor does the operator input such data. BTW if the engine makes 200 ft-lb as in this last example, should we assume it's awesome due to that torque figure? No, if that's its redline or peak power rpm, it will at best be able to keep up with 600's. Nothing awesome about it, it's purely a product of dividing by a low rpm number instead of a high one. If the dyno thought it was spinning twice as fast, it would have reported half the value. It doesn't signify road performance, doesn't signify what's reaching the rear wheel if rpm is different.

Hey, isn't that exactly the point I was stating that you disagreed with?

Yes it is. Perhaps having to work out the problem makes it clearer? If you say I'm wrong, show it!!!!!!!!! This is not a matter of "opinion," and a "How it Works" little article isn't going to do it for you -- nor is implying Isaac Newton would agree with you going to do it for you -- if you can't do this. These are straight questions, if you're right you should be able to show it, which you surely have not so far, not remotely so.

The hp is 100 under a given condition, what torque should be recorded on the dynograph, Workman, and how do you get it?

If under another condition the rpm was twice as high and the hp was still 100, what would that do to the torque figure reported on the dynograph, Workman, and why? How does this disagree with my statements?

A bike putting out more driving force at the rear wheel at any road speed will have a lower reported "torque" figure if the engine spins much faster to do it, because the measurement is divided by the engine rpm; but in practice the higher rpm doesn't reduce performance. Being impressed by high reported torque figures of an engine that spins slower, can result in illusion. It doesn't represent higher torque at the rear wheel, or higher driving force, if it's from being a slower-turning engine. That's why at the same "speed" on the dyno, a H-D puts out less driving force on the dyno's drum yet gets a higher reported torque figure (depending on the model of H-D.) Ditto for this diesel above. Sorry you disagree, but it's true, and it's true for the reasons stated.

A local dyno'er here will only throw the bikes on the drum, too much of a PITA to find the ignition hook-up,I suppose. The dyno sheet has only a hp curve/line,no torque...says he can calculate the torque if you want.

jeff

duhhhh, right under the headlight fluid upper hose :wink:

Gotta have the engine rpm to produce the torque curve or numbers, because that's required in the calculation. You have to divide by it whether working directly from data from the drum, or from the hp data derived from the drum.

You CAN do it, even after the fact, as he offered to do, by computing engine rpm based on the speed in mph at each data point, and information provided on the bike's gearing. Take hp at each point, multiply by 5252, divide by engine rpm corresponding to the speed at that point, and there you are. Same thing, ultimately you have to divide by engine rpm to get the reported torque curve. Whether it's from ignition or calculation from the gearing. But ordinarily the torque curve on a dynograph or values that are reported are not gotten this way: it's from the dyno using rpm off the ignition and dividing by that.

To give an example using gearing: using round numbers that work out conveniently, if the bike measured say 50 hp at a speed of whatever mph, and it turns out that the gearing is such that the engine should have been spinning 2626 rpm at that speed, then that gives 100 ft lb of torque as the reported value:

50 hp * (5252 rpm ft lb/hp) / 2626 rpm = 100 ft lb

If from the gearing calculation the engine should have been spinning four times that fast (10504 rpm) then 1/4 that much (25 ft lb):

50 hp * (5252 rpm ft lb/hp) / 10504 rpm = 25 ft lb

Etc.

The same measurement at the rear wheel, or drum, gives different reported torque values according to the engine rpm, in the above way.

Or alternately, a reported torque value perhaps somewhat larger than another value, but with division by a much smaller figure for engine rpm, will represent actually a much smaller output at the rear wheel or drum at the same speed.

As one example, the 120 ft lb torque-at-less-than-half-the-rpm Harley, once it has to go through the necessary gearing for any given road speed, winds up being gutless compared to a 90 ft lb Twelve. The Kawasaki actually produces much more rear wheel thrust at same rear wheel speed than the Harley, since it does not need to be geared nearly as tall to produce that speed; but the nature of the calculation gives the above result. Ditto for the diesel bike or any low-revving engine, unless the torque is increased in as great a proportion as the operating rpm is decreased.

This is what I was saying from Post 1 here. That is how it works.

Regardless of any claims that seances channelling Sir Isaac Newton would reveal his support for Workman's denials...

Try and think of it like this.

Torque is a force.

HP is a measure of that force along with time and distance.

You can't know HP without knowing torque. In the case of the dyno, it reads the torque of the drum, not the motor. The RPMs are different than the motor because of gearing, but that doesn't matter for calculating HP. Notice I said 'calculating'. The reason you need the ignition hooked up is to convert it to coincide with the engine's RPMs. Never the less, the dyno is measuring torque.

There is no point in debating this, it is a fact.

Nope, it's not a fact.

What you are doing is something I was seeing, and noted in above posts, that you were going to drive yourself into, as the only way to try to salvage your attack. And sure enough here you are.

Convert the discussion to torque at the drum, which no one was talking about and no bothers reporting, you never see it on a dynograph or a technical article. Insteaed of speaking on the same wavelenght that everyone else does where the torque refers to the figure that represents torque at the crank (albeit a figure reduced by drivetrain losses.)

But you think this is a victory if we descend to this alternate type of torque, drum torque? Sadly it does nothing for you. A torque figure that's ever going to be given that people accept and want to read, that will be the figure representating the crankshaft (admittedly minus driving losses.) And how do we do this? Well, it's simple enough take the drum torque, multiply by the drum speed, and then divide by engine speed. The faster the engine was spinning, the more you divide its number down and give it a lower torque figure, for same output at the drum.

Or, you produce the hp figure -- which you can do without knowing the engine rpm, thus proving that the engine hp figure is NOT computed from the computed torque figure (by the way, how long has it taken you to notice that? It's kind of deadly to your argument.) And then with that you can derive the torque curve from gearing if you like. You have to divide down: the higher the engine was spinning, the more you divide down to yield a torque number; or the lower it was spinning, the higher that makes the reported torque figure since you're dividing by a lesser number.

Workman, why is that, if it's like you say it is you know what you're talking about and I don't, that you repeatedly can't answer straight questions, you have to duck? If it's like you say it is, you should be the Jedi able to clearly explain these things.

If it's like you say it is, you should be able to answer these.

1) A dyno reports 100 hp under a given condition. Now, it can do this without being able to report the torque -- if you don't have the ignition plugged in, the engine rpm fed into the dyno, it isn't able to report the torque -- you are finally going to agree this is true, or come out and deny it? Yes or no?

You tell me what torque figure the dyno should put on the chart and how it is obtained.

Can you do it? What do you need?

To repeat: The hp is 100 under a given condition, what torque should be recorded on the dynograph, Workman, and how do you get it?

2) If under another condition the rpm was twice as high and the hp was still 100, what would that do to the torque figure reported on the dynograph, Workman, and why? How does this disagree with my statements?

Since I can answer these, if you continue diving out and being unable to answer, let alone show where I'm wrong, then you just don't have it on this, Workman. Trying to fight (totally needlessly) on a subject you didn't know enough about.

I wouldn't go that far. :shock:

You have no idea what you are talking about. You keep mentioning torque at the crank, I have no idea why. It has nothing to do with this conversation. We are talking about torque at the rear wheel. This is what is measured by the dyno. A dyno measures torque and calculates HP. The torque is measured at the drum(the rear wheel spins the drum). The torque of the spinning drum is measured by the dyno and that torque figure is multiplied by the drum's rpm/5,252.

This is how it measures HP without the ignition attached:

Easy to figure if you know the RPM of the drum and the torque(turning force) of the drum as provided by the spinning rear tire. For example. If the drum measures 100 foot-pounds of torque(turning force) at 5252 RPMs(drum rpm), then you take 100 foot-pounds of torque and multiply this times 5252(rpm)/5252. This equals 100 HP.

We can come up with 100 HP even if the drum spins faster. For example: Lets say the drum is spinning at 10,504 RPMs. Lets say that at 10,504 RPMs(drum), the drum measures 50 foot-pounds of torque. Then you multiply 50 foot-pounds of torque times 10,504/5252 which equals 100 HP.

This is why it doesn't matter how a bike is geared or what gear it is in. A dyno measures the torque(turning force) of the spinning drum -then- multiplies it by the RPM of the drum divided by 5252. This is an undisputable fact. This is how the HP number is derived. In order for you to show the HP curve(or torque curve) in relation to engine speed, you need to know the engine speed which is done with an ignition wire. If you know the torque curve or the HP curve of an engine in relation to its RPMs, then you can easily figure the other.

Even without an ignition wire attached, you can still get the torque curve(and HP curve) in relation to engine speed. All you need in order to do this is to know the exact gearing, then you can extrapolate from that the torque curve(or HP curve) in relation to engine speed.

I don't care if you don't believe this, but you would be wrong. This is not a political discussion, it is science. Fact, not opinion.

What a surprise! You ducked the direct questions you were given, that you couldn't answer, that if you'd tried to answer you'd have been led, or forced, to recognize reality. However, that's just another in a long pattern of your doing the same, ducking what you can't answer, and operating in denial of the fact that you can't back yourself up on given points. Anyhow, now on to your post:

You have no idea why?

Because the torque figures that are published for an engine represent torque at the crank (if measured at the rear wheel this is without accounting for losses), whether measured directly at the crank (preferable) or measured at the rear wheel with computation to convert rear wheel hp to this torque -- namely, torque = hp * 5252 / engine rpm.

It's stated simply as "torque," but it's not the torque value at the rear wheel, which is a far higher -- and variable according to what gear you're in and what sprockets you have -- figure due to the gearing. Perhaps many think it is, obviously you do, but it's not.

Of course the figure is lower, by about 10-15%, than when using a crank dyno. When using a rear wheel dyno, you report the hp as "rear wheel hp" or rwhp, but you do not report the torque as "rear wheel torque" as that's not what it is: that is an entirely different thing, vastly affected by gearing.

Instead it's the rwhp times 5252 divided by engine rpm, as I told you.

All this is understood by those understanding these things and therefore not explicitly stated on dynographs and so forth -- I can see where you could have gotten confused into thinking the torque figures reported on rear wheel dynos are rear wheel torque, but they're not. However by now it's been explained to you many times.

It has EVERYTHING to do with this conversation and the torque figures being discussed of the diesel, as well as the published torque curves you constantly see for bike and car engines and peak figures, represent this torque, not the torque the rear wheel has as multiplied or divided by the transmission to a completely different and changing (according to the gear) value.

A bike torque value has to be a different one in every gear, Workman -- in your world, thinking that torque figures represent the torque at the rear wheel. The gears change that. That's what gears do. They change torque and rpm, but not hp other than slight loss.

The rest of us don't work that way. We use torque figures that represent the crankshaft, and we get the same torque figure regardless of whether we do the run in 4th, 5th, or whatever. Though the gearing completely changes the torque arriving at the rear wheel. Amazing, innit?

Comprende? How much peak torque does a stock 12R have? 380 ft lb? I mean, when you talk about torque, you talk about torque at the rear wheel don't you, and in 6th gear that's what the stock bike gives, if my calculation is right. Or does it have 415 ft lb? I mean you might believe in dyno runs in 5th gear not 6th. Or perhaps 459 ft lb? That would be about right at the rear wheel in 4th gear.

Funny, I don't remember seeing figures like this anywhere, or anyone talking about figures like these, or anyone finding a need to say which gear their torque value was gotten with....

That, of course, is because people are not talking about that kind of torque. Not the torque at the drum or at the rear wheel, but rather estimation of crank torque from the rear wheel data, by dividing out by engine rpm -- that you disagree with.

NO ONE was talking about torque at the rear wheel -- except for me pointing out that it winds up being completely different from the engine's torque due to gearing, with lower revving engines getting their torque reduced far more by the gearing than with higher revving engines, which post you disagreed with -- because this is not a generally published figured. It's a completely different figure (or set of figures in each gear.)

You obviously don't understand that while the reading is taken at the rear wheel, the torque value actually at the rear where is a drastically different number, multiplied or divided (typically divided) by the gearing, different for each gear, and that actual torque is not generally reported. Rather the torque figure, even when measured at the rear wheel, undergoes math to correct it to representing torque at the crankshaft albeit not accounting for losses. That's what the number represents -- obviously you didn't know.

It is equal to the hp at that rpm (as measured at the rear wheel) times 5252 divided by the engine rpm -- just as I said it had to be divided, but you disagreed.

You've answered a question not asked, not disputed, and not being talked about. Where did I ever say the hp couldn't be measured without the ignition? I certainly did not. I said you don't get the torque value without it, and you still haven't explained why not, because you don't understand why not.

What you don't understand is that the torque the engine itself produces cannot even remotely be estimated -- even besides driveline losses -- at this point. You don't have a publishable or meaningful figure for torque, because the torque has been multiplied or divided by gearing in ways the dyno doesn't know, different for each gear, different for whatever sprockets the bike is using.

So how does the dyno produce the torque curve?

By dividing out by engine rpm, just the way I told you Workman.,

[deleted, not quoted -- yaddity yaddity that has nothing to do with disproving anything I said, or adding any illumination to anything, basically where correct either saying the same as I already had, or adding nothing that was disputed.]

Doesn't disagree with anything I said -- in fact it IS what I said, but omitting the fact that the way this is done is dividing by engine rpm, the key point I stated at the beginning, that you disagreed with.

On my part, it is science and fact. On your part, it is arguing against something without knowing what you're talking about on the relevant points.

You disagreed with completely correct statements, you have yet to show them wrong in any way, and further you've displayed fundamental misunderstanding (see above.)

Bye-bye, Workman (on this thread) -- this has been explained, re-explained, re-re-explained, and by now re-re-re-explained to you beyond any reasonable patience.

If you don't get by now that you divide, or the dyno divides, by engine rpm to get the torque curve and reported peak torque, and therefore the points I stated all follow, you're never going to to get it. And that's OK. Not everyone will, and that's OK too. But probably some have understood and maybe gotten something out of it.

You came up with all this crap about 'published' torque numbers, 'readings at the crank', and all kinds of other crap that I'm not even talking about. You go off half-cocked about 50 different things unrelated to anything I said to start with. I am only talking about how a dyno works, is that so hard to understand? Nothing else.

The very first thing I said was, and I quote,

"Trenace, you have it backwards. A dyno measures torque, not HP."

This was in direct response to you saying that a dyno measures HP and calculates torque.

I didn't say shit about 'published' anything. I am talking about dynos and how they work, nothing else. You write 10,00 word essays about all kinds of shit having nothing to do with how a dyno works. The only damn thing I am talking about is how a dyno works. Why do you insist on bringing up all that other unrelated crap? Can't you stick to a subject?

I will make this as simple as possible. The physical force that is sensed by the dyno is called torque. It uses this 'measure' of torque along with the RPM of the drum to 'calculate' HP. Without an ignition wire hooked up, you can get a reading for HP but you cannot determine at what RPM you are producing the HP reading. You will know the peak and not even know at what RPM it peaks at. Never the less, the HP reading is 'calculated' from the torque of the drum along with its RPMs. The torque curve is what is 'measured' by the machine but it is the torque curve of the spinning drum which is a product of the motor*gearing*tire size. To have that torque curve(or HP curve) coincide with the engine RPM, it is necessary to know either the engine's RPMs or the gearing and tire size. Otherwise, you get the peak torque number for the drum, not the motor. HP does not vary due to gearing, torque does. Torque is first 'measured', then converted. The HP 'calculation' is derived by the original 'measurement' of torque from the drum.

You may continue to to insist that the world is flat but just because you believe it, doesn't make it so. But you can believe whatever you want, I don't care.

I want one....Diesel+Boost+propane+N20 = Wild power

I wonder... though it's different than what you're talking about, would propane-only perhaps allow a diesel to operate to higher rpm, due to perhaps faster burning with propane being a gas, vs. droplets of diesel? That -- burn rate having a hard time keeping up with high rpm -- is one of the reasons naturally aspirated diesels don't match what gasoline engines can do for specific output. I have no information on that at all but it seems like a possibility anyway. Anyone know?

On the dyno and torque matter -- most definitely not trying to explain to anyone having read the above, as it's well explained there, but for anyone jumping to the end or just wanting to have the gist of it:

The dyno in measuring drum torque and speed, can and does measure and report horsepower from this. However that above data is insufficient to measure the engine's torque, which is something completely different from the drum's torque (and not just by driveline losses, but by a factor of many times, typically.)

The dyno can plot hp versus road speed while not having engine rpm, but cannot plot values for engine torque vs road speed or provide the engine's torque figure. It's not a question of lacking a scale to plot against, but one of lacking the information required to determine magnitude, how many ft lb the engine torque is.

Doing this requires dividing by the engine's rpm, typically obtained from the ignition. That rpm can also be determined from calculation of gearing and the drum's rpm, but either way it requires division by the engine's rpm.

For these reasons, when an engine is reported to have so many ft lb of torque, this actually itself does not predict how much torque is applied to the road, and does not represent the drum torque produced on the dyno: because of the division-by-engine-rpm factor.

An engine with a higher torque figure than another could actually produce much less torque at the drum -- or on the road as you're riding. This happens if the engine's operating rpm range is much slower. Such an engine, because of requiring taller gearing to achieve same road speeds, can wind up delivering less torque to the rear wheel despite a higher value for the engine's torque.

Simply knowing that an engine has a high torque figure -- e.g. the Harley-Davidson FLSTFSE Fat Boy has 100 ft-lb of torque -- is a terrible predictor if one doesn't consider this factor. Now, while the Hardly engine has this 100 ft lb of torque and the stock 12R only 90 ft-lb, even when the 12 is geared for much higher top speed the 12 will stomp the Hardly in a top-gear roll on. If in a gear giving same maximum speed, a more even test, the murder of the Hardly would be absolutely devastating. But, not what someone with only a light understanding of dynos could have predicted from the torque figures.

If that's ever been a puzzler as to how it is and why torque figures can be deceptive that way, the above is the reason: because of division by engine rpm in converting the actual measurement at the drum to the reported measurement for the engine. Which are worlds different.

I see that apparently the matter of what the dyno measures and how it does it and the mathematical method involved and most importantly, the significance and meaning of the reported figure may be subtle or elusive and certainly missed by some, but it's worth understanding for those that will and helps explain many things. That is why I have tried to explain it.

Just one more smack and this dead horse will be glue!!!!

Bwahahahaha

My mouse needs a new scroll wheel

Hey... this time it wasn't my fault!! 8) 8)

Luckily, I have a system, tho...

Just wait till I now start explaining, say, dyno correction factors, and Workman starts announcing, in attempted rebuttal, "George Washington was the first President of the United States, Trenton is the capital of New Jersey, DIN stands for 'Deutsche Industrie-Norm,' the Declaration of Independence was signed in 1776, etc etc etc and therefore you have it backwards Trenace, you think the world is flat," so I then explain dyno correction factors again, causing him to again deny it while adding in similar stuff, and then I....

Anyway, I was probably wrong in thinking anyone was interested in the previous matter, how the practical significance and predictive value of a torque figure as well as its derivation depends on rpm, other than being interested in disagreeing. No indication of the number interested being anything but zero (nothing new there probably.)

The one and only thing I discussed was correcting Trenace by my stating that dynos measure torque and they calculate HP. They absolutely do not and cannot directly measure HP. Just trying to prevent the spread of bad information. Any mention of any other subject is Trenace arguing with himself. :roll: :roll: :roll:

I'm always interested in technical theory. :wink:

However I get to read core dumps for a living, I avoid them like the plague when I'm not on the clock.... 8)

How does a dynamometer work?

If you want to know the horsepower of an engine, you hook the engine up to a dynamometer (or dyno). A dyno places a load on the engine and measures the amount of power that the engine can produce against the load. Imagine it like this: if you started your engine, had no load on it and floored it, it would run so fast it would explode. So, on the dyno, you apply a load to the floored engine and measure the load that the engine will handle at different speeds. The dyno takes hundreds of readings throughout the rpm spectrum and then measures the torque that the engine can pull against the drum. Then, it instantaneously calculates horsepower from the torque and plots it all on one graph.

Not like it matters, but I think this is what work-dood is sayin'... 8) 8)

I got it here:
http://www.dynamometerservices.com/FAQ2.htm

That is correct. Measures torque and calculates HP.

When you think about it... That's the only way it could happen... Torque is a force... HP is a calculated value involving force over a specified time... :wink: :wink:

Just my $.02...

And I agree with you 100%.

This is what I learned, the way its always been since time began in my corner of the garage (as far as I can find) and unless the laws of physics changed last week I don't know how it could be different.

I am certain that somewhere in the 2,817,233 words in this thread there is a theory Trenace is trying to prove, but I got a headache trying to figure out what it was.

Is what I'm saying truly being missed?

Workman is saying things that were never being denied, and apparently honestly thinks they refute what I was saying. They don't.

Do we really have to go through this again?

Hp can be and is calculated from drum torque and speed, but the engine's torque cannot be and is not calculated from only the drum's torque and speed.

Just isn't so. Say the drum torque was 300 ft lb at a drum speed of 80 mph.. you can't tell me the engine's torque (try it!) though we can compute the hp.

Rather, the engine's torque can be computed only by math dividing by the engine's rpm. Precisely as stated in the first post, but disagreed with. And a consequence of this is, what actually is on the dyno could be for a given engine compared to another, much less torque at its drum and will be much less torque at the rear wheel on the road, can be reported as a higher engine torque value if the rpm divided by was a low rpm.

Yes, I understand that at a superficial level people may read somewhere, as is so, that a dyno measures torque, or perhaps have read more accurately that the dyno measures drum torque, and having read this, what I'm saying that it measures hp without knowing the engine's torque and requires engine rpm to compute engine torque, is not obvious or may even be counterintuitive. However, it's also not that complicated. Who knows perhaps I do not write clearly.

If I have succeeded after all this in communicating what I was saying to no one, then so be it...

And Blitz, as for your thinking that disagreement with me on these points is correct, can you tell me the engine's torque where the drum torque is measured at say 400 ft lb and the drum's speed is 80 mph?

If you cannot then where am I wrong? Why can't you, what do you lack?

Even if I tell you the hp is computed as say 100 hp under that condition, can you tell me the engine's torque? Again, if you cannot, then where am I wrong? Why can't you, what do you lack?

Or are you going to "do a Workman" and, being unable to answer, just skip right past as if nothing was written above? I'm used to it from him, hopefully you'll do better and try to answer.

It's not so much that Workman had many wrong statements... it's that regardless of the many correct statements he had, regardless of George Washington being the first President of the United States or whatever, they do not refute what I was stating. Somehow you have missed this, Blitz.

Also, if you can show me where measurement of force through distance within given time does not give hp, or that these are not direct measurements, please do. If it is untrue that a dyno can be unable to report an engine's torque while being able to report its hp (as measured at the rear wheel after losses), contrary to my statements, please let us know. I believe there may be fundamental lack of understanding of what's involved, when such things as these or their equivalents are stated.

And if as you say you can't find the point of what I was saying, well, obviously I'll never get through, it sure as hell was hammered home often enough!!!

However there was something there, exactly what was stated, and it is significant and relevant.

Lets go back to square one Trenace.

1) Are you disagreeing that a dynamometer measures torque (at whatever medium) and calculates horsepower from that figure?

2) Are you implying that your theory applies to a chassis dynamometer but not a crank dynamometer?

Answer those two questions and cut the insults to workman out and we'll continue. 8)

Damn Blitz, c'mon.

I thought you might do this, might refuse to answer the questions I asked you above. Not because you're a bad person, but because answering them or realizing being unable to do so except by the means I stated, results in proving what I was saying. Accordingly I made a point of making clear I was asking you to really do so, they were not just rhetoric.

Not only don't you do so, you imply I'm insulting Workman by stating the fact that he has a record of doing that exact same. Well, if saying the truth about whether one answers questions or avoids them is an insult, then I am forced to that type of insult. It's something I've encountered with him repeatedly, this thread being no exception, to a point of absurdity, which makes fruitful discussion -- something that's 2-way on both sides -- about impossible. Actually it's probably fair to say completely impossible.

Now you're doing the same.

I'll gladly answer your questions, I have no problem doing so, but it would be more fruitful if you answer the ones I asked you first, truly.

I am not disagreeing with or agreeing with anybody Trenace.

When it comes to physics and mathematical equations (unlike politics and moral dilemna's) there is black and white, no gray.

There is one constant:

HP=TORQUE * RPM / 5252

Since there seems to be a big dispcrepency with that mathematical equation somewhere in the bowels of this thread, I will go back and read the entire thread.

After I read this entire thread and try to figure out where the major conflict is, I will post my thoughts. :wink:

Fair enough!

Also keep in mind that the equation you accurately cite is precisely equivalent to, fundamentally same as:

Torque = hp * 5252 / rpm

...and that neither the rear wheel's torque nor drum torque is even close to the same as engine torque or necessarily each other; and also, incidentally, that torque is not precisely a force as claimed somewhere above -- any more than area is a length -- and more generally speaking is not conserved or even approximately so.

Further that hp is not "torque over time," as claimed somewhere above. You can have any torque you want over any time you want and still have zero hp. Having wrong beliefs like that leads to wrong conclusions. (The equation 1 hp = 550 lb ft/sec refers to the product of linear force and speed, not torque divided by time.)

Lastly, that torque is linear force perpendicular to a lever arm multiplied by length of that lever arm, so the units are not force, but force times distance, e.g. lb ft. Where the linear force is determined but the lever arm is not known -- e.g. the radius of the rear tire is not provided but the force exerted on the dyno, the push of the rear wheel, is determined -- then though the force is determined (which btw if multiplied by linear speed indeed is a direct measurement of hp) the torque of the object, e.g. the rear wheel, supplying that force is not; let alone the torque of the engine.

(The above is of course not an obstacle to the dyno measuring its own drum torque, which indeed it does as part of the above, but who looks at or bandies about drum torque figures, a purely internal value. And further if drum torque figures were provided, they would not suffer from the particular misleading aspect I was pointing out nor did I say they would, though they would add another. The whole issue of drum torque was adding something completely unnecessary to the discussion and had nothing to do with the diesel bike or general significance of torque figures for bikes. Pointless to beat it around, it has little relevance to bikes as the values are never published and further it is entirely dependent on the arbitrary matter of the drum's radius.)

Not all the above was explicitly stated anywhere above I don't think, but will help in following it, I think.

I vote this gets moved to HOSTILE DEBATE.

TTT

O.K., trenace - Now you're starting to piss me off...

There's a bunch of grown men arguing over the internet about how a dynomometer works when the answer has already been given several times (by workman). This is a fuckin' motorcycle website, & I really don't care exactly how a dyno works. But when I looked it up in multiple places, workman was right.

You're right, I did mis-speak when I said that HP was "force over a specified time...", however, I think the fact that HP is a calculated value (not measured) was my point, and you seem not to disagree with that.

Please let it go.

Well Go, if you wish to assume I'm wrong, you can.

You are by the way missing that I've posted that Workman has made many correct statements. That's not the issue. Never stated everything he said was wrong, just that his disagreement of my points was wrong. Your finding various statements of his that are right (though not all of them are) does not change that.

If you wish to state that no one should post explanations that perhaps others aren't understanding, you can. If you wish to post that the rule is, the guy who was disagreed with or is not understood must be the one to stop answering and explaining, well, that could be your rule but it would be arbitrary.

If you want to delete or move the post, you can.

But why not consider the fact that rather simple questions which illustrate my point, neither Workman nor Blitz could answer -- although Blitz has promised to try.

Consider the idea that maybe there's more to it than you realized, and maybe the concepts were harder to get across than I expected, but still valid.

Or figure me to be a fool, whatever you like.

And be pissed off, if you like. However, it's being pissed off for not liking hearing that you and others have not understood something that you thought you did.

In the meantime, if you understand the matter and I do not, will you answer the very simple and key-to-the-matter questions asked to Workman -- the ones in bold, with his name right in the questions -- and to Blitz? If my statements which were objected to or denied are wrong, and you understand the matter, that should be easy enough. As was the case when the questions were asked -- and avoided.

Or if you find them puzzling and cannot, then will you agree there is more to the matter that you have not yet understood? Not that there is anything wrong with that -- no one understands everything, I certainly do not, but I do understand the points I have made on this, and they are in fact very relevant to bikes, and understanding "just what the fuck" that torque figure means and what it does NOT mean, what it implies and what it does not imply.

Or will it be more refusal not only to answer direct, straight questions that you have no answer to, but refusal even to acknowledge them, just continued insistence you're right and I'm wrong? I think that's weak, actually utterly lame, but it seems to impress you, given the tone of your post above.

Saying "I don't know the answer to that question" opens a door to understanding of that question. The above sort of bull-headed refusal to even recognize the existence of questions or points raised is the path to not understanding and absolutely does not result in two-way communication or anything productive.

Blitz is striving to answer these. I'm expecting you'll find some actual communication there.

trenace - Here's the point, clear & simple: You've made more of this than it's worth now & the original facts (as germane to topic or not) are lost in the above diatribe.

What started as comments on an interesting diesel M/C has deteriorated into (what seems to be) a never-ending hashing of words, in the end proving nothing.

I don't want this to seem a personal attack... far from it. I appreciate seeing debate here, & you've contributed often. I went back & re-read the beginning of this thread, & the present acrimony is not necessary. I think you might be well-advised to heed your own advice & consider that your explanation of how a dyno works (complete with elaborate models) might be flawed.

This is only my opinion. I don't think you're a fool, nor am I convinced this needs to be moved to Hostile... If you consider this the ramblings of someone who doesn't understand what you've explained, then don't bother to respond. I won't be offended.

All I gotta say Go, is we've got people who claim to understand the matter, that avoid straight and simple questions key to the matter that if I were wrong, they could devastate me on... but they duck the questions every time in one case, and first time in other case (but promises to get back.)

And we've got at least one person -- hint, he's criticized unfairly all the time :wink: -- that even after that's pointed out, doesn't seem to consider that to be the slightest evidence of possible lack in the other side, and thinks the problem is with the facts of the person who finds the need to duck not a single question.

OK, if you believe so. I have become clearly convinced that the matter here is more difficult than expected, or my explanation is too poor, probably really should have started out with just a single subpoint and built with time over that. I won't be surprised at all if Blitz "gets it" but it's pretty apparent that at a single reading most won't.

It certainly won't be gotten across so long as those questions not only remain unanswered, but no one that can't, even acknowledges they can't and wonders why not, wonders what is needed and why. (Those that can answer them, will find themselves confirming the points I made.)

But so long as we're seeing only avoidance of those questions, I wouldn't be betting that the avoiders have got the handle on this one. Just as a general rule, in those situations, that's rarely the case. Not that that's the best way to decide things but it's one way, if the matter is hard to puzzle out.

If anyone doesn't want to understand it, not worth it, that's fine! But pretty absurd to "take sides" on something one doesn't understand sufficiently.

Also:

Well, looks like you won't! :wink:

Or at least certainly chose not to, and in what seems to be the new style, just act like you weren't even asked, just bull past it. Somehow that's getting pretty typical. Frankly I think it makes it pretty pointless. Why should I post anything with any content -- anything that not everyone already knew -- whatsoever? I really should not. If I'm just typing to walls that don't even acknowledge what's typed, not even when particularly brought to their attention, even specifically asked, then what's that? A pitiful waste of time with no chance of communicating anything not already known to the avoiders, if that's the norm as it seems it now is.

Forget it. Did my best to explain something interesting and useful though perhaps difficult and not elementary, where a superficial look clearly can be deceptive and has been to more than one person here, but was simply ill-treated for it. Your loss not mine.

Trenace said:
You said 'measured HP'...your words, not mine. HP cannot be 'measured' by a dyno, it is a 'calculated' value. Simple fact of science. This is the subject of my rebuttal and only this. You bringing up anything else is an attemp to obfuscate the issue and distract from the fact that were...WRONG!

You seem to be unable to accept the fact that you can be wrong about something...or anything. As usual, you attack the messenger and avoid the message. You write 10,000 word rebuttals that bring up multitudes of other issues unrelated to the subject at hand and impune the character of the person you are debating. Your insults don't bother me, I just consider the source. I actually find it humorous because I know I'm getting under your skin. You should really learn to relax more. :wink:

I suppose going along with a person repeatedly ignoring what he is asked directly and repeatedly ignoring points made and information provided, goes ignoring the fact that someone has said they will not discuss a matter further with that person because they have done so more than enough already, and because of the above reasons. And indeed I will not. I tried more than enough. That's what generated so many pages already.

Perhaps there will be a rational discussion with someone who doesn't have to avoid -- let alone repeatedly, invariably avoid -- direct, key-to-the-matter questions: someone like Blitz, or perhaps there won't if he finds time or interest lacking to work through this matter which does require thought and effort and no one else finds it either. In any case it's clear that the matters here won't be communicated except with such persons willing to have that sort of honest discourse -- actual 2-way communication on both sides -- but unfortunately obviously impossible with those who will not.

Come on boys, we can all play nice. 8)

Actually, I spent several hours reading this thread late last night and there are some very interesting points made (on all sides of the fence) which have piqued my curiousity but to which I am not sure I know the answers. Certainly not enough to stake my name on.

Now, once I get interested in something I gotta know the bottom line. 8)

Be patient here, I have a call in to somebody who has forgotten more about Dynojet dynamometers than I'll ever know. I think when its all over we'll all be pretty knowledgable about dynos. :wink: