New ct20b record. 365rwhp @ 22psi. Gen2 3sgte

[strx7]

has anyone ever hooked an engine dyno up to their driving hubs? cause that is the only true way one can say that X amount of power is being lost through the drivetrain on that particular vehicle

Those figures were on a front engine rear wheel drive set up too. I think its fairly accepted that that driveline set up looses more power through it than a front engine/front wheel drive type set up.

at the end of the day, hub/rolling road figures are best used for comparing before and after gains or comparing 1 car to another on the same dyno, at the same shop.

[sergei]

Realistically 50Hp is already a lot of heat.
for example 50kW induction furnace is capable of melting ~ 10kg of steel.

[strx7]

Realistically 50Hp is already a lot of heat.
for example 50kW induction furnace is capable of melting ~ 10kg of steel.

but you are thinking about it the wrong way. the wheel HP readings aren't loosing X HP thru the drivetrain, they are merely reading a HP difference. Unless you hook an engine dyno up to the wheels, no one can truely say how much power is truely being LOST in the drivetrain.

[saft]

don't ignore the effect of ramp rates as well

you are accelerating a mass (drivetrain, and in the case of wheel dynos the mass of the tire/rim and roller(s)) you will see lower power figures with a faster ramp rate.

its not all thermal loss

[RedMist]

Realistically 50Hp is already a lot of heat.
for example 50kW induction furnace is capable of melting ~ 10kg of steel.

but you are thinking about it the wrong way. the wheel HP readings aren't loosing X HP thru the drivetrain, they are merely reading a HP difference. Unless you hook an engine dyno up to the wheels, no one can truely say how much power is truely being LOST in the drivetrain.

You never loose energy. You simply convert it. In this case to either sound or heat. As the drivetrain doesn't make a hell of a racket then a clear majority is converted to heat.

[saft]

You never loose energy. You simply convert it. In this case to either sound or heat. As the drivetrain doesn't make a hell of a racket then a clear majority is converted to heat.

only in a situation where the measurement is taken with slow or no acceleration of the drivetrain

[Malcolm]

but you are thinking about it the wrong way. the wheel HP readings aren't loosing X HP thru the drivetrain, they are merely reading a HP difference. Unless you hook an engine dyno up to the wheels, no one can truely say how much power is truely being LOST in the drivetrain.

Wait, WTF? Is the implication here than anything that's called an "engine dyno" reads exact power figures, while anything that's called a "chassis dyno" is full of errors and variation? You do realise that they're fundamentally the same apparatus, but one is configured to mate to an engine while the other has rollers which allow a car's wheels to drive its input?

[Al]

flywheel HP is the only TRUE HP, because all types of hub and wheel dynos read different!!!!!! why cant people comprehend that.

Time to move to pomgolia mate.

They love BHP there with their coast down chassis dynos runs.

The B stands for bullshit.

[saft]

sweet, if flywheel is what matters I can claim an extra 80hp

[strx7]

Time to move to pomgolia mate.

They love BHP there with their coast down chassis dynos runs.

The B stands for bullshit.

did you actually read my post which said

many years ago a vehicle was run on dynojet, dyno dynamics and dynopak dynos as an auto. the owner then converted it to manul, and ran all 3 dynos again. before the engine was put in the car it was also run on an engine dyno. the results were....
Dyno Pak manual read 9% less than flywheel
Dynopak Auto read 11% less than flywheel
Dynojet Manual read 15% less than flywheel
Dynojet Auto read 17% than flywheel
Dyno Dynamics Manual read 27% less than flywheel
Dyno Dnamics Auto read 29% Less than flywheel.

therefore engine hp readings have got to be closer to true actual power than the great range of RWHP figures the same car can produce........

[strx7]

You do realise that they're fundamentally the same apparatus, but one is configured to mate to an engine while the other has rollers which allow a car's wheels to drive its input?

Yip, sure do. The one that mates to an engine has less things between the item actually making the power and itself to give discrepencies

[sergei]

You never loose energy. You simply convert it. In this case to either sound or heat. As the drivetrain doesn't make a hell of a racket then a clear majority is converted to heat.

only in a situation where the measurement is taken with slow or no acceleration of the drivetrain

What do you think happens to "lost" energy when it is accelerating?
It will eventually be converted to heat.
Say a flywheel (I assume you imply that energy is lost on inertia), when you spin it you put energy into it. You slow it down - you take the energy, if you slow it down via friction - energy comes out as heat.
You cannot lose energy.

[saft]

its not lost, its simply going into accelerating the drivetrain

and therefore cant be measured at the wheels, but isnt being turned into heat or noise

[fivebob]

its not lost, its simply going into accelerating the drivetrain

Care to explain where the "lost" energy goes, because that explanation is BS

and therefore cant be measured at the wheels, but isnt being turned into heat or noise

Conservation of energy says it is being turned into other forms of energy, heat, noise etc.

[Scottie]

the dyno debate

someone will soon tell us that "dynos are a tool man! all they are for is to tell us if the conditions that are changed from one dyno run to the next have had a difference".

Also, funny how all the dyno manufactures sell these machines for thousands of dollars that give such varying results. You would think they need to be calibrated somehow before being sold. 1hp/Nm is a standard unit ffs.

And how the first question asked by people when talking about 'performance' cars is "how much powa!! you got?"

[iOnic]

So yeah. I think the topic of conversation does sweet skids.

[sergei]

its not lost, its simply going into accelerating the drivetrain

and therefore cant be measured at the wheels, but isnt being turned into heat or noise

It is being turned into heat, once you take off the acceleration. Additionally the rotational inertia of the gearbox is no where near the power levels we are talking about, it is not accelerating indefinitely, and not at a huge rate either.

With proper gearing you can accelerate car flywheel, by hand, to rev limiter RPM in less than a minute. How much power does a human output? Flywheel has more inertia than gearbox components anyway.

We can bring the formulae into this, but they are too tedious...

Let say moment of inertia of a car flywheel is 0.1 m^2 kg.

The Energy stored in flywheel is E = 0.5 * ( 0.125 m^2 kg) * (150/sec)^2 = 1406J

So to accelerate this flywheel to 9000rpm in 10 seconds it would consume energy at rate of 140.6W. A good athlete can do this in 5sec .

Note: I could have made a mistake in my calculations and assumptions. The moment of inertia of a car flywheel is and ballpark estimate.

EDIT:
Here how I derived moment of inertia:
I used:
0.3m diameter fly wheel
10kg mass

the formula is following: 0.5 * 10 kg * (0.5 * 0.3)^2 = 0.125 m^2kg

[saft]

its not lost, its simply going into accelerating the drivetrain

Care to explain where the "lost" energy goes, because that explanation is BS

and therefore cant be measured at the wheels, but isnt being turned into heat or noise

Conservation of energy says it is being turned into other forms of energy, heat, noise etc.

its being conserved but not measured in the drivetrain

its still rotating at the end of the measured run.
at a faster ramp rate more energy is used (as a percentage of what was produced overall) in accelerating the driveline.

most dynos we run over here dont do the wind down measurement.

[saft]

alright, now accelerate the driveshafts and diff(s)

input shaft to 8000 rpm
in my case i dynoed the car in 5th (.807), with a 4.11 diff ratio

(was hitting the torque limit of dyno in 4th)

ended up overall ratio of 3.32:1

theoretical wheel speed was 284kmhr

in 8 seconds
the driveshaft reached approx 10000 rpm, the half shafts etc 2500 rpm

[fivebob]

its being conserved but not measured in the drivetrain

Oh really, where is it hiding then?

its still rotating at the end of the measured run.
at a faster ramp rate more energy is used (as a percentage of what was produced overall) in accelerating the driveline.

Energy in must equal energy out, momemtum of the drivetrain is minimal and once the drivertrain is up to speed there is no further storing of the energy.

If your statement had any truth to it this begs the question of what happens to the lost energy when power is measured at a constant speed in the case of a brake dyno like Dynapack.

most dynos we run over here dont do the wind down measurement.

Because it's a BS measurement.