FYI:

Power (kW) = (Torque (N.m) x RPM x 2 x Pi) / 60,000

A dyno actually just reads the torque value and calculates power in this manner.

Edit: Stupid forum not putting my divide signs up properly...

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

Then why the tractive effort at all if kW is calculated from Nm?

I'm starting to realise why I hated physics

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[COLOR=Black]Liberty GT Spec B tuned 240 HP & 372 Nm at the hubs.[/COLOR] "Instead of banning high performance cars - ban low performance drivers"

Further to your post Kato - another Lib ASN member has piped up with the equivalent formulae and replied . . .

GTB_Lib

I can give an estimate based on the ratio between the stock power figure and the paper spec.

Paper
194kw (flywheel)
350Nm

Stock dyno run
130kw atw

Ratio between atw and flywheel
0.67

Stage 4 dyno run
210kw atw (at peak tractive effort)
4200rpm (at peak tractive effort)

estimated flywheel power
210/0.67=313kw
estimated flywheel torque
313*1000/(4200*2*pi/60)=712.5Nm


All of that is based on the guesstimated ratio between on paper flywheel power and measured power at the wheels on a dyno and the assumption that the dyno would produce completely consistent results on any day in any conditions

FWIW, those 9549 and 9543 figures are a simplification of the 1000/(2*pi/60), the difference coming from using different roundings for Pi

So another willing to give a "guesstimate" of around 700 Nm

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[COLOR=Black]Liberty GT Spec B tuned 240 HP & 372 Nm at the hubs.[/COLOR] "Instead of banning high performance cars - ban low performance drivers"

Oh FFS...

Maths are pretty simple.

Tractive effort does not equal torque. And it should not come into anyone's equations.

Also the crack head who is suggesting that a 210kw at the wheel car is a 313kw at the engine needs to lay down the pipe.

My Evo does 200+kW atw, by his calculations I should have 700Nm at the fly too and destroy every car out there.

Tino's car does say 450kw at the wheels, by those calculations he has 1425Nm or some such shit.

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

give up Andrew, I did long ago

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Funny looking German Subaru

Well, I certainly give Kato and Dave a lot more credit than others "floating round the net".

I'm just trying to get my head around this concept of tractive effort - mind you, considering that most that I read deals with train locomotion I wonder why anyone would use/quote it on a dyno.

PS - Never knew your EVO had that much torque Kato

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[COLOR=Black]Liberty GT Spec B tuned 240 HP & 372 Nm at the hubs.[/COLOR] "Instead of banning high performance cars - ban low performance drivers"

I like.... Andrew put that up on your forums and see what they have to say.. hahah

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I'm a jockey kunts...

Tractive effort includes the following:

The 0.1 factor is just looking at the diameter of the dyno rollers. Someone has said multiply Force (N) by distance (m) = Torque (Nm) - which is correct... but what is this force and how is it being displayed on the screen?

So to convert a tractive effort to torque you need to know:
- the tyre size
- the diff ratio
- the gear ratio

Then to calculate torque you would do the following:

Torque (Nm) = (Tractive Effort x Tyre Radius in meters) / (Diff Ratio x Gear Ratio)

I know sweet fa about Liberties, but assuming a 4.44 box and a 1:1 gear on 215/45R17's this gives a torque value of 492Nm. Sounding better...

Someone post up the accurate tyres/diff/gearing and lets compare that to reversing the power formula above.

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

maths is great,

you can even roughly calulate hp and torque from volumetric efficency and rpm.

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Long live the WRC

Looking at a MY08 GT-B

In 4th Gear - Ratio 1.137
Diff - 3.90
Wheels - 215/45R18 = 650 OD

Therefore 7000N is rougly 513Nm

230.7kW roughly is 310hp

Looking at Muggz dyno plot:


Which is a EJ257 producing 307hp and 464Nm... The figures start to get close and seem reasonable... Unlike 700Nm...

PS If he is making 700Nm, he needs to call up AMG/BMW M and let them know the secret!

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]