how do dynos work?

[VSIIBerlinaL67]

i actuly looked up the power figures he told me it had 500 or so nm but only really has 200. so yer i get it now

 

[commsirac]

i actuly looked up the power figures he told me it had 500 or so nm but only really has 200. so yer i get it now

The 500Nm would need to be at a very low rpm, but it sounds a bit high for something in a hilux
If it were producing 500Nm @6000rpm that would be 314kW.
If the max torque was at max power, then max power of 80kW would occur at 1500rpm, which doesnt sound feasible unless we are talking about a 12L boat engine or similar.

Just using the formula: power(kW) = (rpm x Torque(Nm))/9549

 

[Not_An_Abba_Fan]

Energy conversion yes, the engine converts the energy in the fuel to heat. This energy conversion pushes the pistons down spinning the crank shaft. The key word? Spinning. This is twisting force exerted by the crank, which is torque. The output at the flywheel and ultimately at the wheels is measured as torque, then it is converted via a formula to kW or HP. The gearing behind the engine is what is doing the work over a given time, the engine is just providing the torque to make this possible.

The same with the water wheel comparison, whatever the drive shaft is acting on is doing the work, the water wheel is providing the twisting force on the shaft so it can transfer it to the working mechanism.

 

[commsirac]

The gearing behind the engine is what is doing the work over a given time, the engine is just providing the torque to make this possible.

.

Davey G force has outlined the conservation of energy principle to you. The energy from the fuel goes to heat which then gets transferred into moving energy in the engine. Then where does it go, into torque.....no, torque is not measured in Joules.

No, the gearing just alters the torque output at the rear wheels. It has no effect on the power or work done....other than gears causing losses due to more friction.

yes the power is calculated from other quantities(which always ends up being power = rate of energy use/production)......as it is in every circumstance as there is nothing which measures power directly.
The magic formula used by the engineers(which Ive already given previously), requires the torque produced and the rpm that the dyno is turned at. The faster the dyno spins at a given torque, the more power the motor is developing. As youve said ^, the key word is spinning. Unfortunately, torque is just the force of rotation, not the rate of spinning. We can have torque without spinning......which has been covered in detail ^)
Both torque and rpm(movement) need to be present to produce power in an engine!

NAAF, this is really school boy physics(which I take from previous posts you didnt do) and it has been put simply enough to you ^.
Obviously you dont want to believe anything davey g force says or I say(I am qualified in this area as it appears also for Davey G). Perhaps get someone qualified in physics or engineering that you trust to go through it with you.

 

[davey g-force]

Energy conversion yes, the engine converts the energy in the fuel to heat. This energy conversion pushes the pistons down spinning the crank shaft. The key word? Spinning. This is twisting force exerted by the crank, which is torque. The output at the flywheel and ultimately at the wheels is measured as torque, then it is converted via a formula to kW or HP.

*Sigh* I'm not disputing any of this (although I don't agree with your next sentence). I'm merely arguing your statement that an engine does not produce power and only produces torque; which is fundamentally incorrect.

 

[vt748]

It would pay to actually do some research before posting something contrary to what Ive posted, I only post on what I know about!.

No worries bud. Seems like you have never been wrong before. Guess this time is a first for you.

Believe what you want.

Power is simply the product of torque and how fast the engine is spinning.

You said it so well. Power is calculated, torque and rpm are measured! Can you measure something that doesn't exist? I figure you can't, but what would I know
I obviously haven't "researched" it as much as you. Still keen on handing out hidings?

Sure a dyno measures an engine's torque and then calculates its power.

Funnily enough your mate said the same thing.

A petrol engine does use the force of the explosion to create its torque

BTW You are really showing how ignorant you are by statements like this. :thumbsup:

 

[levymetal]

An engine uses energy to produce torque.

This is correct, however:

Chemical energy stored inside the fuel is converted to heat energy which is converted to kinetic energy.

This is also correct. Torque is a moving force, kinetic energy is also a 'moving force' as such. So torque is actually energy. The energy goes from the fuel, to the piston etc etc etc to the wheels, and is then transferred to the car itself when the car is moving. Or in this case is transferred to the dyno. For the dyno to measure anything energy has to be physically transferred to it.

OR I'm just talking ****. But that's how I see it anyway.

 

[commsirac]

vt748:
you are really stuck on the idea that since we calculate the power from the torque and RPM of the dyno, then there is no such thing as power? You could argue that there is no such thing as energy too, since there is no meter that will measure the energy of something directly. Considered how the come up with the energy in each serve of your breaky cereal? Did they use an energy meter? No, they measured other quantities and used those to calculate the energy.

I could waste time spending more time explaining it to you, but really you only appear hell bent on trying to discredit me rather than understand the concept: as I said previously to NAAF:

: this is really school boy physics(which I take from previous posts you didnt do) and it has been put simply enough to you ^.
Obviously you dont want to believe anything davey g force says or I say(I am qualified in this area as it appears also for Davey G). Perhaps get someone qualified in physics or engineering that you trust to go through it with you.

 

[commsirac]

This is correct, however:



This is also correct. Torque is a moving force, kinetic energy is also a 'moving force' as such. So torque is actually energy. The energy goes from the fuel, to the piston etc etc etc to the wheels, and is then transferred to the car itself when the car is moving. Or in this case is transferred to the dyno. For the dyno to measure anything energy has to be physically transferred to it.

OR I'm just talking ****. But that's how I see it anyway.

Levy: NAAF has some correct stuff in there....but it is this which causes objection:

An engine doesn't produce power

Unfortunately your own take on some of it is incorrect. You display some confusion between force and energy.
Did you read all my earlier posts in this thread.
Torque is not confined to forces on objects that are moving, surely you've heard of torque wrenches, you can exert a torque and keep it there for ever without any movement. Torque certainly is not energy, perhaps what you have confused is that energy is needed to produce torque in a car engine, however, torque can be created/maintained without energy. Kinetic energy is not a moving force. It is the energy that needs to be given to the body to get it moving to a particular speed or the energy needed to be taken from the body to stop it moving.
torque it is most typically just a force applied at a distance from a fulcrum, or pivot. (for those that know, we can calculate the torque or moments around any point).
The combination of providing a force and movement requires energy(that is why we need to have the torque on the rollers of the dyno and the speed they are spinning at to calculate power), power is just the rate at which energy is supplied/provided.
However, you are right, energy is transferred to the dyno from the engine. The dyno either gets hot, powers a generator .....the energy doesnt disappear.

 

[vt748]

vt748:
(I am qualified in this area as it appears also for Davey G). Perhaps get someone qualified in physics or engineering that you trust to go through it with you.

Really? So tell me what are your qualifications? What are you qualified in? What do you do for a living?

I figure that you are neither a mechanic or mechanical engineer, because if you were I don't think that you would be explaining the combustion process as explosions. Come on champ tell us all about it. I am waiting for my hiding, (Although generally I prefer a light spanking ).

you are really stuck on the idea that since we calculate the power from the torque and RPM of the dyno, then there is no such thing as power

Yep mate pretty stuck on that idea. Show me a dyno that measures power and uses RPM to calculate torque. Better yet show me a dyno that will measure both since your engine evidently produces both. All the dyno's I have ever seen measure torque to calculate power. Like I said in my first post power is a calculated measurement for engineers to compare engines. Your engine does not produce power it produces torque. Torque and RPM as has already been mentioned, are used to calculate the power figure. So arm chair experts like yourself can go to the pub and brag about how much POWER your engine produces.