how do dynos work?

[17UCK!]

i see/here people sayin i went in n got my car dyno tuned n they got 40kws out it.. just wondering exactly how it works? and dose it work on a vs commo lollllll

[adamc11]

To put it simply... you drive your car up onto the dyno and put your rear wheels (for rwd car) on a set of rollers. When you accelerate though the gears, the rollers spin and the dyno measure the power your car has at the wheels
To say someone got 40kw out of it (they probably mean 40rwkw (rear wheel kw as dynos measure in kw at the wheels)) it means that they probably had a tune at the same time... i.e. dyno tune... a professional tuner tunes your vehicle on the dyno so you get the most amount of power out of it.

[17UCK!]

yeh but like how do they " tune " it?? wat do they axully do 2 make u get more kw? thats wat i dont understand.

[impulsesv6]

dynos dont measure rwhp/rwkw

they measure torque and calculate the hp/kw from that

Dynamometer - Wikipedia, the free encyclopedia

[greenfoam]

yeh but like how do they " tune " it?? wat do they axully do 2 make u get more kw? thats wat i dont understand.

Mostly the extra power is from more spark advance, the factorys don't tune cars to all their potential for various reasons. So most cars can have the spark advance increased so that by the time the piston reaches the top of it's stroke the burn is allready well underway and so you get more pressure, more effciency and more power. On modified cars that have had parts changed to get more effciency from the motor they can have more fuel added in those areas to gain a bit more power again. That's about it

[Not_An_Abba_Fan]

dynos dont measure rwhp/rwkw

they measure torque and calculate the hp/kw from that

Dynamometer - Wikipedia, the free encyclopedia

Beat me to it.

Power is just a calculation. It doesn't really exist. James Watt thought it up when wanting to talk about the effort required from a pony to move coal in a coal mine. At best it was an estimation because horse couldn't sustain the effort over a period of time at the figure that Watt came up with.

It has been passed on through the years as a figure that people use to rate the available power of a machine. An engine doesn't produce power at all, it produces torque (twisting effort), this is measured and converted to hp or kW.

To answer the OP's question a bit more, a dyno loads up the engine by providing resistance to the rollers and measures peak torque. This is when the engine loses it's ability to spin the rollers at certain revs.

[17UCK!]

cheers greenfoam . that was the kinda answer i was lookin 4 lol..

[Weekend Warrior]

Beat me to it.

Power is just a calculation. It doesn't really exist. James Watt thought it up when wanting to talk about the effort required from a pony to move coal in a coal mine. At best it was an estimation because horse couldn't sustain the effort over a period of time at the figure that Watt came up with.

It has been passed on through the years as a figure that people use to rate the available power of a machine. An engine doesn't produce power at all, it produces torque (twisting effort), this is measured and converted to hp or kW.

To answer the OP's question a bit more, a dyno loads up the engine by providing resistance to the rollers and measures peak torque. This is when the engine loses it's ability to spin the rollers at certain revs.

torque is actually "turning force" and is calculated by the force x radius hahah good old physics class taught me that one

[Not_An_Abba_Fan]

Turning force twisting force, same thing. The effort required that causes something the turn or twist.

[davey g-force]

Beat me to it.

Power is just a calculation. It doesn't really exist. James Watt thought it up when wanting to talk about the effort required from a pony to move coal in a coal mine. At best it was an estimation because horse couldn't sustain the effort over a period of time at the figure that Watt came up with.

It has been passed on through the years as a figure that people use to rate the available power of a machine. An engine doesn't produce power at all, it produces torque (twisting effort), this is measured and converted to hp or kW.

To answer the OP's question a bit more, a dyno loads up the engine by providing resistance to the rollers and measures peak torque. This is when the engine loses it's ability to spin the rollers at certain revs.

Not sure if I mis-read your post but I'm not sure what (watt?) you're trying to say here. Of course power exists and it is very real.

Power (measured in watts) measures the rate of energy use or production per unit of time; i.e. 1 watt = 1 joule of energy per second.

An engine produces BOTH power and torque - hence why all vehicle manufacturers quote both kW and Nm figures. Also why two cars can have the same power, but one can be quicker than the other due to it having more torque.

[Not_An_Abba_Fan]

I am referring to the term horsepower and how it relates to an engine. An engine doesn't produce power, all it does is create a twisting (or turning) force. Which is torque. The power figure is calculated using a formula based on torque and RPM.

Without going into too much detail here is a site that explains it pretty well. http://www.vettenet.org/torquehp.html

[davey g-force]

Yeah, that's all fine, but your comment "an engine doesn't produce power" is not correct.

Sure a dyno measures an engine's torque and then calculates its power, but that's not to say the engine isn't producing power. It is expelling energy over time, thus it's producing power.

[impulsesv6]

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

there is a calculation

[burnz]

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

there is a calculation

in short NO only estimates, unless you remove the motor and measure on a power absobsion engine dyno.


and the other post abba i think, james watt. one BHP= 3000 Lbs per foot/ per minute.
and torque is 5252 or 5454 one of the two.

[commsirac]

I am referring to the term horsepower and how it relates to an engine. An engine doesn't produce power, all it does is create a twisting (or turning) force. Which is torque. The power figure is calculated using a formula based on torque and RPM.

Without going into too much detail here is a site that explains it pretty well. http://www.vettenet.org/torquehp.html

Im with Davey G force here

NAAF, engines are devices that can do mechanical work, the faster they do that work the more power they have. They do "work" because they provide a turning force and they are able to turn. 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.
Power is simply the product of torque and how fast the engine is spinning.
You can have a small amount of one and a large amount of the other to produce the same effect
ie a v8 producing 300Nm at 2000rpm will produce the same power as a smaller engine producing 100Nm at 6000rpm. Either one will produce the same effect on the vehicle, given that the gearing is adjusted accordingly.
You are correct in that power is merely calculated on the dyno. The force that is used to move the rollers is calibrated and controlled and the power is then calculated by the speed at which they are spinning, the torque figures for the engine can only be worked out if the rpm of the engine is known. 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.

For those that care:
power can be calculate by the force x speed
The effective turning force at 1m from the crankshaft is given as the torque in Nm. The speed has to be in metres per second and it it is the speed that an object would be going if it were attached at a metre radius from the crankshaft.
1rpm is equivalent to a distance of 2 x Pi metres per 60 seconds.
or 1rpm is equivalent to 0.105m/sec

the v8 producing 300Nm at 2000rpm can be calculated to be producing:
300 x 2000 x 0.105 = 63kW

or more simply
9549x power(kW)/rpm = torque(Nm)

[greenfoam]

: ) This thread is classic ( :

[17UCK!]

yeh go me i started it lol.. but u gave me an answer forwat i asked:P

[VSIIBerlinaL67]

how about diesel cars that have fk all power but make heaps of torque

[Swordsy]

how about diesel cars that have fk all power but make heaps of torque

Because they generally don't rev as high.

Horsepower = (Torque * RPM)/5252

KW is just replacing the number at the bottom to the measurement(foot pounds to nm) that torque is in.

[vt748]

Im with Davey G force here

Sorry Davey G is wrong

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.

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.

[VH commodore]

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]

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]

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.

[commsirac]

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]

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.