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how do dynos work?

VH commodore

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how do you calculate rwhp into fwkw, and torque for that matter

there is a calculation
a VERY ROUGH ESTIMATE to convert fly wheel hp to rwhp...is fly wheels kw = rear wheel hp. so ecotec is bout 148fwkw= about 200fwhp which = 148 rwhp.......just a really rough guesstimate......any1 dyno'd a standard ecotec before to elaborate?

there is no accurate way to convert flhp to rwhp as there are countless variables
 

davey g-force

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Sorry Davey G is wrong
Please explain to me how an engine is NOT producing power?

Again I reiterate; an engine is producing energy over time, thus it must be producing power.

Power (W) = Energy (J) / Time (s)

I know that dynos calculate power by measuring torque at different rpm and loads, but that's not to say the engine isn't producing power.
 

commsirac

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Sorry Davey G is wrong




Torque is tranferred to the dyno.

Power is calculated from the torque value. The engine produces torque and engineers have come up with a calculation (power) that helps them compare different engines. ;)
It would pay to actually do some research before posting something contrary to what Ive posted, I only post on what I know about!

The engine has to actually drive the dyno, the power from the engine is transferred to the dyno.....the dyno has to get rid of the energy. As I explained above:
Power from the engine is transferred to the dyno and the surroundings(heat in the tyres etc). The power developed could be measured by looking at how much energy the dyno gains/produces per unit time, it depends on how it is braked, but is not as easy to do as measuring/monitoring the resistance force. (measuring how much energy the dyno gains is a combination of how much hotter it gets, how much electrical power it puts out(some have generators which power the mega electric fan they put in front of the cars etc).
They could have the dyno stirring up a giant container of water and measure the temp increase from this to come up with a power increase.
If they did it this way it would be as stupid as saying "power doesnt exist because dynos only measure temperature", or if we used the dyno to drive an electrical generator and monitored the voltage and current output, then saying the dyno only measure voltage or current....equally ridiculous.
Simply power is the rate at which energy is provided/used. It is a real quantity, but can be evaluated in a number of ways depending on the data available.
Perhaps ask for some clarification if you are not sure here.

Measuring the resistance force that the rollers provide at their particular radius(the torque) and multiplying that by the rpm of the rollers tells us how much power is being produced on the dyno. Both the torque measured at the rollers and the speed they are moving at have to be known to come up with a power figure. Torque by itself is a meaningless number when it comes to looking at engine performance, as Ive mentioned before:
I can provide just as much torque as the worlds best production car V8 by standing on the end of a metre spanner, but can I make a car move along at any where near the rate of an engine producing 500kW? of course not.

I understand the misconception. Its just something that has been perpetuated by motoring enthusiasts unversed in the laws of physics when they say torque is the only thing that matters in an engine. Unfortunately, without rpm its nothing.
 
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commsirac

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how about diesel cars that have fk all power but make heaps of torque
What about them? yes by design the diesel motors of the same capacity produce more torque at below 3000rpm than petrol motors. Many people describe this as torquey, which is fine, but it just adds to the confusion for most of thinking that torque is the only quantity that matters or power doesnt exist and other nonsense. It would be better if it was just described as the motor is producing more power than the same sized petrol motor at the same lower rpms.
The diesel motor would win the race up to 3000rpm, but would come a distant second as the petrol motor is able to go for another couple of thousand rpm producing more or less the same torque. Of course if it was a proper race, the petrol engined car would be operated at 4000rpm+ for the whole time making the low speed power advantage of the diesel irrelevant.
 

Not_An_Abba_Fan

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An engine uses energy to produce torque. Get your head around the definition of torque first then you may be able to understand what is actually being said.
 

commsirac

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An engine uses energy to produce torque. Get your head around the definition of torque first then you may be able to understand what is actually being said.


A petrol engine does use the force of the explosion to create its torque, but it doesnt mean a motor doesnt produce power. Each open throttle intake, if you like, produces roughly the same explosive force on the piston. The more of them we can get the motor to do per sec or per minute the better and the more power the engine is said to have.
The same cant be said in reverse, we can produce torque without using energy. ie we can put 70kg on the end of metre spanner to produce 700Nm or torque all day using absolutely no energy at all. Or I could possibly put my bicycle on the dyno and get close to the same torque readings as a v8 with the right gearing and enough friction on the back wheel. So what's the difference between me and a v8?, how fast we can move against the torque of the rollers.....its called power.

NAAF, you are just on a ticket to another hiding here, you are talking on subjects which are out of your depth..

After all you hot air making personal attacks on myself in this thead, climate change threads and the like I noticed you werent able to come up with anything for :http://forums.justcommodores.com.au/883006-post671.html.
 

davey g-force

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An engine uses energy to produce torque. Get your head around the definition of torque first then you may be able to understand what is actually being said.
The Law of Conservation of Energy states that energy can not be created nor destroyed. Therefore an engine is using energy to produce energy.

Chemical energy stored inside the fuel is converted to heat energy which is converted to kinetic energy. It's still energy. Therefore, for an engine to be producing energy per unit of time, it must be producing power.
 

commsirac

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Chemical energy stored inside the fuel is converted to heat energy which is converted to kinetic energy. It's still energy. Therefore, for an engine to be producing energy per unit of time, it must be producing power.
concise and correct.
 

VSIIBerlinaL67

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mate mates hilux has ****load of torque but only like 80kw and revs to 6k a excel could beat it
thats why i asked
 

commsirac

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mate mates hilux has ****load of torque but only like 80kw and revs to 6k a excel could beat it
thats why i asked
well its not producing ****loads of torque at 6k if it produces only 80kW. Possibly max power is at 5k or so, which would put the torque at max power at ~ 152Nm......its not a v8.
 
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