Dyno mystery

[conkerman]

10 min in the pub and this would be sorted

Otherwise. OUTSIDE!

[Corvus]

Corvus, you think too much. Obviously you are not having enough alcohol in the evenings. Can I recommend Stowford Press. Things will be much clearer then.

Bloody hell! Someone's watching.

Hee Hee.

Not tried that one. But I shall!

Come on, give us your thoughts on the magical mystery torque tour.

I am not going to go back over 5 pages of posts. I will say, the curves provided by a dyno are a representation of what the engine is doing, utilising various measurements and calculations to derive a dataset that can be compared to other datasets derived in the same manner.

That way, changes can be tracked and analysed and future changes planned. It's a tool. Ultimately what you get from the tool will depend on the skill and understanding of the person analysing the data.

Well put. Can't disagree. But that's more a definition of the objective. You have avoided giving an opinion as to whether the torque curves are abstract. You don't really need to go over the last five pages. The crux of it is covered over the last few posts.

[Corvus]

10 min in the pub and this would be sorted

Otherwise. OUTSIDE!

If you can do it in 10 minutes in the pub, it would only take the same time now. As much as I would enjoy a pint with you, we're stuck with tinternet for now.

Is what I'm suggesting really that outrageous? Or difficult?

Or wrong?

[Herb]

Bloody hell! Someone's watching.

Hee Hee.

Not tried that one. But I shall!

Come on, give us your thoughts on the magical mystery torque tour.

I am not going to go back over 5 pages of posts. I will say, the curves provided by a dyno are a representation of what the engine is doing, utilising various measurements and calculations to derive a dataset that can be compared to other datasets derived in the same manner.

That way, changes can be tracked and analysed and future changes planned. It's a tool. Ultimately what you get from the tool will depend on the skill and understanding of the person analysing the data.

Well put. Can't disagree. But that's more a definition of the objective. You have avoided giving an opinion as to whether the torque curves are abstract. You don't really need to go over the last five pages. The crux of it is covered over the last few posts.

I have reread some of the thread, and I am still a little confused as to what the actual question is.

Most dynos that we would have access to are fairly simple devices. Your standard Dynojet model does not measure power or torque directly. It measures acceleration of a known mass and then derives power and torque curves with compensation for gearing from that acceleration.

These are plotted in an easily understood and used format, against engine speed. The fact they are mostly WOT devices means that the data is of limited use, except as a comparison for peak power and torque.

I would not use the term abstract as that implies it does not exist except in concept. Power and torque are obviously generated by an engine, so they exist. The fact is they are not typically measured directly and hence have to be derived.

[Corvus]

I am not going to go back over 5 pages of posts. I will say, the curves provided by a dyno are a representation of what the engine is doing, utilising various measurements and calculations to derive a dataset that can be compared to other datasets derived in the same manner.

That way, changes can be tracked and analysed and future changes planned. It's a tool. Ultimately what you get from the tool will depend on the skill and understanding of the person analysing the data.

Well put. Can't disagree. But that's more a definition of the objective. You have avoided giving an opinion as to whether the torque curves are abstract. You don't really need to go over the last five pages. The crux of it is covered over the last few posts.

I have reread some of the thread, and I am still a little confused as to what the actual question is.

Most dynos that we would have access to are fairly simple devices. Your standard Dynojet model does not measure power or torque directly. It measures acceleration of a known mass and then derives power and torque curves with compensation for gearing from that acceleration.

These are plotted in an easily understood and used format, against engine speed. The fact they are mostly WOT devices means that the data is of limited use, except as a comparison for peak power and torque.

I would not use the term abstract as that implies it does not exist except in concept. Power and torque are obviously generated by an engine, so they exist. The fact is they are not typically measured directly and hence have to be derived.

Very well put. I need you on my side! You have an analytical approach.

I don't have a question, but an opinion or point of view. That the torque curves are abstract.

I agree with most of what you just said except that you don't see what you just described as abstract. I mean abstract as in "doesn't exist". Of course it is possible to conjure up abstract figures. Just tell the poor little computer false information, which is what you do the moment you tell it that all gear and chain ratios from crankshaft to rear wheel are all 1:1 ratio. Which is precisely what happens.

Take the xbr500 graph, with the three curves. They have the crankshaft, gearbox and rear wheel all running at the same speed. The transmission losses are accounted for, and with respect to power, this is fine. But to have the torque figures for gearbox and rear wheel expressed at engine speed is abstract.

[Herb]

I would still not use your term 'abstract'. The curves in question are corrected to a given standard for air temp etc, and the dyno software will make an assumption on gear ratio.

Therefore the torque and power curves are 'derived'. The accuracy of the derived data will depend on how close the tested gear was to the gear assumption amongst other factors.

The curves are derived curves with a percentage margin for error based on the accuracy of the assumptions.

Given that the assumptions should not change from run to run, and other factors should be corrected for to a reasonable degree, with consistency of set up from run to run, then the derived data is a useful tool for comparison.

[Corvus]

I would still not use your term 'abstract'. The curves in question are corrected to a given standard for air temp etc, and the dyno software will make an assumption on gear ratio.

Therefore the torque and power curves are 'derived'. The accuracy of the derived data will depend on how close the tested gear was to the gear assumption amongst other factors.

The curves are derived curves with a percentage margin for error based on the accuracy of the assumptions.

Given that the assumptions should not change from run to run, and other factors should be corrected for to a reasonable degree, with consistency of set up from run to run, then the derived data is a useful tool for comparison.

My point is not concerned with all the various ambient compensations, just the torque curves.

The assumption on gear ratio is 1:1. That is abstract. Not real. You don't believe that all the gears and the chain are all 1:1. So why are you not able to apply the term "abstract"?

[Herb]

I would still not use your term 'abstract'. The curves in question are corrected to a given standard for air temp etc, and the dyno software will make an assumption on gear ratio.

Therefore the torque and power curves are 'derived'. The accuracy of the derived data will depend on how close the tested gear was to the gear assumption amongst other factors.

The curves are derived curves with a percentage margin for error based on the accuracy of the assumptions.

Given that the assumptions should not change from run to run, and other factors should be corrected for to a reasonable degree, with consistency of set up from run to run, then the derived data is a useful tool for comparison.

My point is not concerned with all the various ambient compensations, just the torque curves.

The assumption on gear ratio is 1:1. That is abstract. Not real. You don't believe that all the gears and the chain are all 1:1. So why are you not able to apply the term "abstract"?

I don't believe abstract is the correct term. Abstract implies that something only exists in concept. The engine is producing torque, and that torque can be measured if you have the correct equipment. Therefore it is not abstract.

The dynos we use, can't measure it directly. That does not mean it is abstract, it just means the curves have to be derived by another method.

The curves produced by an inertia dyno would be better described as 'indicative' if you want to imply they are inaccurate or estimated in some way.

[SP250]

Getting down to semantics now.

I have always been happy with the following statement:-

"Torque is the prime mover of weight and horspower is the prime mover of sales".

[slparry]

Getting down to semantics now.

I have always been happy with the following statement:-

"Torque is the prime mover of weight and pie n chips is the prime mover of scales".

Yep I'll go with that

[Corvus]

Herb said: "I don't believe abstract is the correct term. Abstract implies that something only exists in concept."

I didn't mean abstract quite like that, I've described what I meant by abstract, but actually I don't have a problem with using your definition of abstract. Yes, the torque curves in question only exist in concept. They certainly don't exist in reality and any one of you can so easily prove it. Use the hp formula, but be sure to enter the correct speed against the power curve for the shaft in question, not the 1:1 "correction" which only exists in concept.

Herb said: "The engine is producing torque, and that torque can be measured if you have the correct equipment. Therefore it is not abstract."

Absolutely. Except the torque in question is not the one measured. It never happened. It is derived in abstract fashion from a power curve which did happen and is not abstract.

Herb said: "The dynos we use, can't measure it directly. That does not mean it is abstract, it just means the curves have to be derived by another method."

Can't measure what? The torque? The torque values in question weren't measured, they were calculated from a power value, back calculated, using the wrong rpm value applicable for the shaft concerned.

Herb said: "The curves produced by an inertia dyno would be better described as 'indicative' if you want to imply they are inaccurate or estimated in some way."

With respect to the torque curves in question. Not indicative (in fact misleading). Not inaccurate. Not estimated. Abstract. Not existing in reality. Existing as a concept. Very accurate in the abstract way they are derived.

Using the xbr500 graph, because that has curves for three stages in the power train, it has the rear wheel going around at the same speed as the engine. If the rear wheel did go around 1:1 with the engine, making the amount of power shown, then the torque value fits fine. But the wheel didn't go around at the same speed as the engine. So the torque curve is not indicative.

[Corvus]

Getting down to semantics now.

I have always been happy with the following statement:-

"Torque is the prime mover of weight and horspower is the prime mover of sales".

No, it's not an disagreement over semantics. I've acknowledged I'm happy to use herb's version of abstract or my own. Or the one in the dictionary. I've checked and I'm happy it portrays the point I'm trying to make. And failing miserably.

By statistics alone I'm obviously wrong. I'm in a minority of one. But then again none of you lot have convinced me I'm wrong.

I love gear ratios. They don't half muck things up.

[SP250]

Corvus

I don't have to convince you that you are wrong. You may be looking at it from a different angle to others and we are all allowed our own opinion or views.

I love a proper engine dynomometer.
Never used a rolling road yet.

Steve P

I had to read that twice - very funny but also true.

Off up your way tonight for a curry with some mates.

[slparry]

Corvus

I don't have to convince you that you are wrong. You may be looking at it from a different angle to others and we are all allowed our own opinion or views.

I love a proper engine dynomometer.
Never used a rolling road yet.

Steve P

I had to read that twice - very funny but also true.

Off up your way tonight for a curry with some mates.

Cool! Whereabouts?

[Corvus]

Corvus

I don't have to convince you that you are wrong. You may be looking at it from a different angle to others and we are all allowed our own opinion or views.

I love a proper engine dynomometer.
Never used a rolling road yet.

Steve P

I had to read that twice - very funny but also true.

Off up your way tonight for a curry with some mates.

True. It's comforting to think that ones view is right though.

Yes, a. brake dynamometer. It shows torque reaction, plain and simple. Wysiwyg.

The graphs mostly derived from an inertia rolling road aren't wysiwyg. It's difficult to put a definition to what they show, torque wise. Abstract! That'll do.