Dyno questions

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I am very ignorant about how dynos are constructed. Last night a friend rang me and discussed the activities of his mate in Queensland. The guy has a Kawasaki engined bike which he uses for speed records. He was looking for someone with decent dyno skills and found someone in Brisbane who works on nitro/methanol fuelled stuff. On changing from petrol to methanol, and playing around, he found a slight increase in BHP, but a massive increase in torque. He then found the bike was much quicker up through the gears, so the top speed was also higher. My question is about how torque is measured on most dynos, and how it is related to engine revs /throttle opening. I don't know how the energy created by the motor is dispersed on most dynos, and from watching the videos of Kenny Cummins, it looks as though the power readings are taken off the roller which is driven by the rear wheel of the bike. Years ago I was in charge of rocket motor firings. To measure the thrust we used to hang the motors on gimbals made from strong sheet metal strips and direct the force through a computer monitored load cell. ( pants-filling stuff ! ) I suggest that what is important with a bike motor is the forward thrust of the bike in relation to engine revs. Getting a digitised rev counter and load cell with the range and which is sensitive enough to handle what comes off the front of a bike, could be a problem . We used to cut our own crystals and glue them to a substrate, then calibrate them with a dead weight tester. It might be possible to have the bike push against a long lever ? You would be looking for gains in midrange power. How sensitive and reproducible are modern dynos in measuring torque from the roller ?

Rohan, my friend made the same comment as yourself about moving into the modern era and using dynos to measure motor output. I can see merit in the idea, however the practicalities might present a problem. It is easy to be deceived by numbers .

http://www.youtube.com/watch?v=3IWFVyQm29I
 
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acotrel said:
It is easy to be deceived by numbers .
I
If you don't know how a dyno is constructed, or works, or how tuning works on one, then how can that sentence possibly have any meaning ???

Take your bike and have it dyno tuned, and report back here.

Explaining things in words here has previously proved a waste of words, you don't appear to be here to learn anything new.
Just googling to find things out produces a world of new information.
Try it some day, you may learn something...
 

texasSlick

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horsepower = torque x rpm / 5252

the dyno dissipates the power thru an electrical load or eddy current brake that can be controlled and measured. RPM can be easily measured, then torque calculated from the formula above.
 

johnm

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texasSlick said:
horsepower = torque x rpm / 5252

the dyno dissipates the power thru an electrical load or eddy current brake that can be controlled and measured. RPM can be easily measured, then torque calculated from the formula above.
+1
 
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Is the calculation made by computer and displayed as a graph of horsepower vs RPM ?
Rohan,
we have a bike shop which runs a dyno, it is about 60Km from here. I don't think I want to associate with hairy-arsed pseudo-technicians whose only interest is in making a dollar. There are a lot of guys around here who set themselves up as experts, and they really would not know. If you want anything done in NE Victoria, there are a lot of expert engineering shops which do superb work. Forget the motorcycle shops. They are the very last people I would rely on for tuning expertise. There is only one which I would go near, and its owner competes at the top in superbike racing - the rest are useless. Even then, if he delegates to his idiot underlings you could have a problem.

As I understand it most of the dynos in use require the application of 'correction factors' - what is that about ? How is the calibration done, and how is reproducibilty (precision) tested ?
 
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texasSlick said:
horsepower = torque x rpm / 5252

the dyno dissipates the power thru an electrical load or eddy current brake that can be controlled and measured. RPM can be easily measured, then torque calculated from the formula above.
I think you mean "power calculated from the formula above". Torque is a direct measurement of force by load cell.


There is also the all too common inertial dyno where the acceleration of the heavy roller is a direct result of forces from the bike. The acceleration is then used to calculate torque.

The video that acotrel provided a link to above with Kenny Cummings on the 1,007cc Norton is a dual dyno where it can be run with inertial and it also has an eddy brake. In the video the bike is working against the inertial mass of the roller. Kenny was breaking in the motor and not really doing dyno pulls; just getting in one of a few heat cycles.

acotrel said:
Is the calculation made by computer and displayed as a graph of horsepower vs RPM ?
Rohan,
we have a bike shop which runs a dyno, it is about 60Km from here. I don't think I want to associate with hairy-arsed pseudo-technicians whose only interest is in making a dollar. There are a lot of guys around here who set themselves up as experts, and they really would not know. If you want anything done in NE Victoria, there are a lot of expert engineering shops which do superb work. Forget the motorcycle shops. They are the very last people I would rely on for tuning expertise. There is only one which I would go near, and its owner competes at the top in superbike racing - the rest are useless. Even then, if he delegates to his idiot underlings you could have a problem.

As I understand it most of the dynos in use require the application of 'correction factors' - what is that about ? How is the calibration done, and how is reproducibilty (precision) tested ?
Most dynos I have worked with very accurate and yield reproducible results. There is an incredible amount of data acquisition and integration. You really need to go and use one or see one in use to get a good grasp of the capabilities including exhaust gas analyzers (real time) which can chart along with torque, power, rpm etc.

There are various "correction factors" and I am not an expert nor am I that knowledgeable about the intricacies of the various correction factors (DIN, SAE etc). Some of the factors correct for temperature, pressure (air density) to a standard reference so that when you come back another day you can compare apples to apples and adjust for atmospheric changes. Best to select a factor and stick with it. Dynojet offers a stand alone (free) software where you can analyze the hell out of (and apply different correction factors against) the raw data files.
 
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Dances, In the link that Brett just posted, it says this about chassis dynamometers:

'Integration of the dynamometer control system with automatic calibration tools for engine system calibration is often found in development test cell systems. In these systems, the dynamometer load and engine speed are varied to many engine operating points, while selected engine management parameters are varied and the results recorded automatically. Later analysis of this data may then be used to generate engine calibration data used by the engine management software.'

In my case the closest dyno is in another country town, in a bike shop. They really going to do THIS ?
I think that if I take my bike there, they will take my money, and give me a number - meaning what ?
I've been a scientist for too long, and the biggest lesson I ever learned is that 'the system runs on bullshit'. I will take your advice and go and have a look at them, however I'm sure I will be wasting my petrol getting there .
I've got absolutely no interest in what horsepower my motor turns out. I am however interested in improving it's mid range (torque). At present I am using 6DP6 Mikuni petrol needles instead of Amal Xs and Ys in my 34mm Mk2 methanol carbys. Mikuni needles come with three stage tapers, and I'd like to try the alternatives. Do you know how the selection is made in MX bikes ?
There are two ways of getting around our local circuit fast. One is 'point and squirt' - it doesn't suit a fragile Norton motor.

Rohan, before you start crapping on about stoichiometry, the other day I told someone on this forum never to predict outcomes when developing his bike. The stoichiometric mixture with hydrocarbon fuels is the explosive mixture, maximum torque is probably elsewhere .
 
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I plan on taking my BMW to the dyno in aug/sep. There are two I know of, one where you get a print out of HP and they don't do any tuning, the other is a guy who uses it as a tuning tool to get your bike performing as it should.
My understanding is that you can load up the bike, get a reading then go on to change jets, timing etc.
As far as I'm concerned, you have to have a base line measurement before you can make any changes.
I know I can get around my local track in 1.27 consistently, so hopefully some tuning of my existing set up can eek out a few more HP and I can get below that.
My butt dyno suggested my mates R90s had more mid range punch so I'm expecting a dyno curve reflecting this.
Should be interesting.
 
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Combat, a lot depends on the circuit. If it is mainly fast sweepers and long straights extra horsepower (top end) is great. If it is tight and twisty and you can put work in on the other guy, you need more midrange and possibly a better gearbox. Also you need more flexible/nimble, less stable handling. I once rode a 900ss Ducati, it felt as though you could jump up on down on it while it was cranked over, it was so stable - obviously designed for Imola ?
 
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acotrel said:
Rohan, before you start crapping on about stoichiometry, the other day I told someone on this forum never to predict outcomes when developing his bike. The stoichiometric mixture with hydrocarbon fuels is the explosive mixture, maximum torque is probably elsewhere .
Stoichiometric is NOT the explosive mixture, its the fuel air ratio where ALL the fuel is burned - we are talking in engines here.
Going lean runs hotter.
We did mention that more like 12:1 is better for maximum power.

If you've never had it on a dyno and explored the mixture with a gas analyser, how do you know anything about stoichiometric ??
Methanol in particlar is very forgiving of mixture strength - wasn't it Phil irving that published, in writing, you could have your mixture strength up to 50% too rich, and the bike still pulled strongly. Getting it spot on is an exercise in getting too close to the danger zone - for a race bike ??

What actually does "never to predict outcomes when developing his bike" actually mean ??
Is this some deep and meaningful comment on life, or a throwaway line ...
 

Holmeslice

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The DWS 1007cc Seeley puts out some mighty impressive numbers.

But, who really cares about the number? It's all relative.

Example:

My last session, my own race bike put out about 29hp at the rear wheel
I'm quite happy about that, because the time before, it put out 28.

See you all in turn 1
 
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Holmeslice said:
The DWS 1007cc Seeley puts out some mighty impressive numbers.

But, who really cares about the number? It's all relative.

Example:

My last session, my own race bike put out about 29hp at the rear wheel
I'm quite happy about that, because the time before, it put out 28.

See you all in turn 1
What Holmeslice does not say is that it also puts out barrel loads of torque. As a friend used to say about Mack diesel trucks; "not much on revs but can haul 98 ton of rock".

I think Holmeslice is right in acotrel's camp on this torque thing. :D
 
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Rohan
'Methanol in particlar is very forgiving of mixture strength - wasn't it Phil irving that published, in writing, you could have your mixture strength up to 50% too rich, and the bike still pulled strongly. Getting it spot on is an exercise in getting too close to the danger zone - for a race bike ??'

That comment by Phil Irving must be the biggest joke of all time. The guys around here seize upon it and run the bike on methanol absurdly rich. The facts is that methanol hides up the tuning errors. To get the most out of it, it is as difficult as petrol to get right, as lean as possible without blowing up, is best. There is no need to fear going too lean on as four stroke race bike, unless it is on a very long straight, and even then we set the mains with a plug chop. If it is too lean elsewhere, the bike is a pig to ride. With a two stroke it is a completely different matter. Even with petrol, the mixture requirements change as the crankcases heat up, so you choose when you want to go slow during a race - early or late. With methanol, that factor is deadly.
There is another common belief - 'if you've got a torquey motor, you don't need a close box', it is said by people who have never used a close box.
My comment about never predicting outcomes, was that until you've actually tried something on a circuit, you will never know what an 'improvement' will deliver.
 
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acotrel said:
Dances, In the link that Brett just posted, it says this about chassis dynamometers:

'Integration of the dynamometer control system with automatic calibration tools for engine system calibration is often found in development test cell systems. In these systems, the dynamometer load and engine speed are varied to many engine operating points, while selected engine management parameters are varied and the results recorded automatically. Later analysis of this data may then be used to generate engine calibration data used by the engine management software.'

acotrel, you really don't need a developmental test cell system for your bike; that would be over the top. Best for you to visit a dyno owner/operator and talk to him or her. Best if you could see it in action, not so much the "dyno in action" but what the operators do while loading the engine and what they do afterwards (jetting, ignition etc) and what information they are using to make the decisions. It's a learning experience and I understand you don't want to throw yourself to the wolves. Have a go at it and you will learn something, even if you decide not to go to a dyno.

Even if you get your bike "dialed in" you still need to know what to do at the track when atmospheric conditions change. I pissed away two good race weekends chasing down ignition problems which ended up being firmly in the atmospheric/jetting area. This last summer at two race venues it was unusually hot with unusually low pressure and my needle jet turned out to be sub marginal. Shame on me for being slow to recognize it; my head needed a tune up more than anything else.
 
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acotrel said:
There is no need to fear going too lean on a four stroke race bike, .
And you have all the race wins to back this statement up ?
This would be interesting to explore on a dyno, wouldn't it....
 
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Rohan, If you are ever jetting an 850cc Norton twin to use methanol using Mk2 Amal carbs, a main jet of size 700 will never seize or burn pistons unless the tip of the needle is too big, and the motor never runs on the mains. Otherwise if it is too lean elsewhere the motor will cough, it is a dead give away and you won't usually do damage, unless you persevere .
 
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The only track I had a clear top end advantage is now closed to motorcycles thanks to V8 taxi parades with lots of bike unfriendly concrete.

the other tracks are a only 3kms long and a mix of tight corners and shortish straights. I'm limited in gear ratios to the Std BMW box and a selection of 3 final drives.

I have good corner speed, and you can lean a BMW with the motor raised 30mm over to the edge of the tyre. Its a very stable bike, an transferring your weight smoothly helps a lot to.

I have one favourite corner that's a long 180 and I go around the outside of a couple of 850 featherbeds ....I love those moments, priceless.....of course they leave me on the straights.

I watch some riders moving around the bike mid corner and the bikes don't like it.
 
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acotrel said:
Rohan, If you are ever jetting an 850cc Norton twin to use methanol using Mk2 Amal carbs, a main jet of size 700 will never seize or burn pistons unless the tip of the needle is too big, and the motor never runs on the mains. Otherwise if it is too lean elsewhere the motor will cough, it is a dead give away and you won't usually do damage, unless you persevere .
It would be interesting to put an exhaust gas analyser on that and explore where that is in the scheme of things, wouldn't it. ?

Having a fuel that does most of your engine cooling for you if you get it very wrong is very different to out in the real world.
Most of us here are road bike oriented.
Having it survive a few laps too lean is very different to doing x thousand miles AND getting home again each time...
 

texasSlick

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to dances with schrapnal

the dyno measures power. a load cell measures force. torque is force acting over a distance.

to acutrel

a graph of hp vs rpm, torque vs rpm. are usually produced from a dyno run. this is all at the rear wheel. correction factors adjust results to a "standard" temperature and atmospheric pressure so results from a run on another day can be compared.
 
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