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how do dynos work?

Discussion in 'Dyno Figures' started by 17UCK!, Sep 13, 2008.

  1. commsirac

    commsirac Banned

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    So I take it from that response you didnt do high school physics?

    What are my qualifications and profession? more than enough to comment on the differences between torque and power.

    Sorry, I dont reveal personal information on a public forum for several reasons, which i wont go into.
    Regardless, If I was able to tell you what my qualifications were and what I did for a living, you probably wouldnt believe me.....then you'd be asking for proof, where would it end, Id have to post a copy of the transcripts for my uni results or pictures of my degrees? Then whose name appears on the degree, is it really me, then Id need my passport photo....no thanks.
    The reality is anyone can claim to be anyone on the internet, it is more important to look at what they say.
     
  2. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Energy and power are two different things though. We aren't disputing the transfer of energy, the point I was trying to get across is that the process of calculating the 'power' output of an engine is the measuring of it's torque then using a formula to work out it's 'power'. James Watt originally wanted to quantify a steam engine's ability to do work by comparing it to the rate at which a horse could move a weight over a distance in a set time. The term 'Horsepower' is an approximation, as no two horses could do the exact same amount of work in a given time. Horsepower was used because it was what was understood by the people at the time.

    While power does exist, I still contend that an engine doesn't 'make power' it makes torque. The engines ability to make usable torque in certain rev ranges is converted to kW or HP by a formula. If the engine were to 'make power', then why isn't there a device to measure it?
     
  3. vt748

    vt748 New Member

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    Yeh mate I did high school physics. Ha Ha a long time ago. Getting a bit old now I am afraid. But I always remember my first physics lecture at university when the lecturer told us to forget everything we learnt about physics at high school, because basically it's the baby version, to give you a taste so to speak. But i am sure you already know this.

    Since then I have among other things built engines professionally for 8 years. I obviously am not in your league as any engine I built only produced torque. The power always had to be calculated.

    I have also have tested engines on engine dyno's for 2 years.

    Believe or not, couldn't care less, you obviously do alot of research and are confident in your own beliefs. Maybe next time you can do a bit of research on the explosions that happen in YOUR engine that produces POWER. :thumbsup:
     
  4. commsirac

    commsirac Banned

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    post removed....when you keep banging your head against a brick wall, sometimes its best to stop.
     
    Last edited: Oct 4, 2008
  5. greenfoam

    greenfoam New Member

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    Well so long as the torque happens as high in the rev range as possible I don't care how it's messured :p because that's how you go realllly fast, you can probably make a 10 second 1/4 mile in a V6 commodore with it's stock 300 nm of torque (if that torque happened at 12,000 rpm) that's why someone smart invented gears!, Power is everything :)
     
  6. commsirac

    commsirac Banned

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    post removed .....futile
     
    Last edited: Oct 4, 2008
  7. vt748

    vt748 New Member

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    :rolleyes:

    Commsirac, mate you just waffle on and on. The original posters question was how does a dyno work. Now we have explanations from you on how thermometers work, how thermocouples work,how much energy is in a bowl of cornflakes, blah blah blah.....You seem to just want to quote what you learnt in your high school Physics class.

    Basically the only thing that has been needed to be discussed is torque, rpm, and power. You contend that the engine produces power and torque, I reckon the only thing that an engine produces is torque. I think I will just agree to disagree with you.

    BTW I was never confused by you using the term "explosion", it just gave me an insight into how much you really now about engines! :p
     
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  8. commsirac

    commsirac Banned

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    You are right vt748, it is pointless me waffling on when the people such as yourself and NAAF, whom I am hoping to convince otherwise, have had these views for perhaps along time and nothing will convince you otherwise.
    Hopefully what I have posted is not wasted on those with open minds.
    You are not going to tell me that you worked on a dyno that only gave your torque readings, surely not? There is no magic formula that engineers can simply plug just a torque value to get a power figure, or perhaps you can produce one.
    The "magic" formula I believe you are talking about is:
    (power(kw) = rpm x torque(Nm)/9549)
    Perhaps the dyno you worked on provided torque and power readings? the power reading could only be arrived at if the dyno was measuring its rotational speed, which they all do.....

    Torque wrenches produce torque......they are not engines
     
    Last edited: Oct 4, 2008
  9. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Torque wrenches meausure torque actually....The force of your arm pulling or pushing the wrench is what is producing the torque...
     
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  10. commsirac

    commsirac Banned

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    If we extend your logi: if dynos only measure torque and torque wrenches measure torque, then a dyno and a torque wrench are the same thing?

    For goodness sake, torque wrenches are machines/levers that are force multipliers(we use them to tighten bolts etc) and they have a scale on them to measure how much torque they are producing.
    They dont have to be pushed on by humans, we can just hang weights off them to create the torque if you like.....but I agree by itself a torque wrench wont do much, I had given up on making sure what I wrote was word perfect.....so you can win some points there.......
    However, the simple point, which has been explained to you(fifty times ^?), is it is very easy to produce massive torques, ie standing on the end of a metre spanner produces more torque than any production car v8, which archimedes worked out just a little while ago.

    Simply most dynos as we know them, measure the torque and the rpm produced at the rollers.........which combined together these two quantities gives us power! Just like we combine the voltage and current that goes through a toaster to give us a power rating.:bang:
     
  11. davey g-force

    davey g-force I'm a sceptic...

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    I still stand by my original comment that an engine expels energy (and thus power) - it has to, due to reasons I mentioned above.

    I agree that we need to agree to disagree. Any further arguing about this by me would be pointless. :D
     
  12. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    That comment may just prove you spend your days in a labcoat. If rapists all wear blue hats and you wear a blue hat, does that make you a rapist?

    A dyno measures the torque of an engine, a torque wrench measures the torque applied to a bolt. It doesn't matter what is exerting the force on the wrench, whatever it is is the thing that is producing the torque, the wrench is just measuring the applied torque. The wrench itself (or the lever) is just multiplying the torque so not as much force is required to get the bolt to the required tightness. Just like the engine is providing the force required to spin the crank shaft.
     
  13. commsirac

    commsirac Banned

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    Once again you have got it only half right, dynos measure torque and RPM
    to be able to give a power figure. If they didnt measure the rpm then they wouldnt be able to provide a power figure.....if they only measured torque then as previously it would be a pointless measurement, as pointless as me saying I could get my bicycle to record a reading of 1000Nm on the dyno.....which could easily be achieved.
    I gather you havent gone to a physicist or engineer to clarify this...suggest you really do that for you own good...unless you want to be forever ignorant on this issue.
    Im finished here.
     
  14. mr LS1350

    mr LS1350 New Member

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    -------------------
     
  15. boonga

    boonga New Member

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  16. burnz

    burnz dah dut dut da dah

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    i got a headache reading that, i wonder how many pills comms had from banging his head.
     
  17. ari666

    ari666 250,000 hits

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  18. -=ApheX=-

    -=ApheX=- Member

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    Figure i'd stick in my 2 cents...

    rwkw - think about this word for a moment?
    Kilowatts is what we are really talking about here... with me so far?
    So the engine creates "Energy" by converting energy! fuel and air + spark = big bang
    This energy cause's an effect by moving a piston to which this energy is transferred... This energy remains the same as the effect of this energy whilst it travels through a spinning crank shaft to the axel then axel to wheels... Keeping in mind this is still energy!
    now... This energy is measured from a Dyno in Kilowatts because this is the energy output it is creating at a measurable force...

    It's is fairly simple to explain when you don't over think what is actually happening here...
    The question was asked how do dyno's work? elaborated how does it measure rwkw?

    So to summerize rwkw is the transferred energy to the wheels from which the engine has produced. energy equating to that of a measurable force... in effect everyone in there own way is correct, but you are all over thinking the simplisity of cause and effect and how we measure such occurances!
     
  19. -=ApheX=-

    -=ApheX=- Member

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    Ohh I wanted to also mention something in regards to Torque in applications, "Not an abba fan" this is not aimed at you...
    Torque from an engine to wheels is similar in essence to that of a torque wrench or driver...
    Elaborate... We try and undo a massive bolt with the handel of a small wrench? won't work very well... not enough applied force... we do it with a longer wrench more applied force is driven through the device in question to turn said bolt...
    Think about this in an engine scenario, Power is applied to the crank spinning an axel, so if we think about it as the maxium amount of force has been applied in the engine and is being expelled through gears, axel, diff to wheels, to road... Torque is but a by product of energy applied earlier to spin something with mass and or resistence e.g. a road!!!
    apologies for double post...
     
  20. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    The point of the whole argument is what do dyno's measure, they can't measure power as power is only a calculation based on what is actually measured, which is torque. There is a thread on LS1 that explains it better.

    Whatever applies the force is irrelevant as the dyno can't actually quantify it, it can only measure the torque required to spin the rollers.
     

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