Member Profile - McDoof

[andy_mac]

Makes sense i guess. How does that translate to virtual dyno style results which are almost half that value in my case. Does that come down to virtual dyno knowing gear ratios, wheel sizes and all the extra data the real dyno typically won't have?
Is that then actually giving flywheel torque rather than wheel torque?

[BillyCorgi]

I am afraid to say that I also cannot understand the dynamometer graph.

If McDoof's car was achieving 163kW at an indicated road speed in 4th gear at the indicated nearly 150 kph point then.....
for a Spec B with 1.137 4th gear ratio and 3.9 final drive and with normal 18 inch low profile tyres, the engine speed would be about 5,500RPM. That is what is calculated. (Is 5,500RPM correct????? Feels low for the H6)
For this speed and this ratio the wheels would be rotating at about 1,240RPM

1,240RPM would be about 130 radians per second.

For 163kW ATW and 130 rad/sec wheel speed, the Wheel Torque (total) would be 1,250 Newton.Meters.
The graph is showing about 625 (units?) of different by a factor of 2.


McDoof, are you able to help?
We love your kWatt numbers, however there may be some other scaling factors that we do not understand?

[BillyCorgi]

I do not now believe what I wrote above.
The details I have access to for the Spec B transmissions that would be in my car and McDoof's car are....
For a Transmission code TY856WVBAA the gear ratios are stated as
1st....2nd....3rd....4th....5th....6th....Rev....T.R....F.D
3.636 2.235 1.521 1.137 0.971 0.756 3.545 1.100 3.900

The maths says that with 18 inch Spec-B wheels/tyres then at 150 kph the engine RPM would be about 5,500rpm.

I drove my car out tonight on the Hume Expressway and the 4th gear was only achieving abut 120kph at about 5,200 rpm.

Rechecking these numbers the alternative 4th Ratio for the 6MT of 1.346 is more consistent with what I observed in my car.
So I do not believe the published ratios?

The 4th gear ratio of 1.346 would be achieving over 6,500 RPM at the 150kph road speed indicated in McDoof's dynamometer printout. This is about where one would expect the H6 to be achieving maximum power.

So, presently, based upon my observations, I do not believe the published gear ratios.

Notwithstanding this analysis, the analysis above on wheel torque checks out.
About 150kph equates to about 1,240 to 1,250 wheel RPM or about 130 wheel radians per second.
163 kilowatts at 130 radians per second equates to about 1,250 wheel newton metres
The dynamometer output is showing about 625 units?
Still different by a factor of two?

[McDoof]

I wonder if the this already has the the calculations made for torque but only considered a rwd car and had not made the necessary changes for the awd numbers. Hence the torque numbers are showing half what you would expect. Our double what you would expect of the the numbers were already calculated

[McDoof]

I should probably mention that each run was done to the fuel cut. So the final drop off is at 7250 RPM. I'm not sure that road speed is 100% accurate on the dyno. I'll do an overlay with known days to map the real rpm numbers to this graph and post that up late today

[andy_mac]

Can't seem to find any real information on that particular make of dyno either..

[McDoof]

Can't seem to find any real information on that particular make of dyno either..

That's because they are custom made right here in NZ by Torque Performance.

[BillyCorgi]

Tried a Google search on "dyno torque RR LT SM" and only turned up these leads
http://www.google.com.au/url?sa=t&rct=j ... OujdI83NBA
http://www.google.com.au/url?sa=t&rct=j ... zH7jZa1Yvg
Both belonging to Torque Performance Ltd 37 Patiki Road Avondale

The first reference lists "Torque at the Wheels". Clearly this is stated to be Newton.metres and at the wheels.
The second reference lists "Tractive Effort" in Newtons.

[McDoof]

I'll shoot a question off to Robin at Torque performance. He would have been involved in building this unit.
As for the gearing etc, we also need to keep in mind that the speedo on your car (and mine) reads about 7 or 8% over. I'm in the process of taking some of my logging data and setting up a map of RPM vs true road speed. Should have something useful in the next day or so. Just need to do a 4th gear pull.

[BillyCorgi]

Hi Nik,
I looked at the output for a BMW M5, that listed tractive effort.
The dyno output listed 339.6kWatts corresponding to 190 kph.

339.6kwatts is 339600 watts
190kph is 52.78 metres per second.

Power = Force x Velocity.
Force (Tractive Effort?) in Newtons = 339600/52.78 = 6434.5
The graph is showing a number about 875
Must be secret Dynamometer Men's magic.

By the way, just saw this on Throttle Happy's Facebook page
https://www.facebook.com/Throttle.Happy ... =3&theatre
You're now famous!

[McDoof]

I've always been famous. Only problem is nobody else knew about it.

[andy_mac]

Getting more famous by the day
https://www.facebook.com/permalink.php? ... 1564911239

[BillyCorgi]

I think definite hero status!
Sure to wear out his centre differential with all that power!

[McDoof]

I think definite hero status!
Sure to wear out his centre differential with all that power!

You offering me a rebuild?

[BillyCorgi]

I think definite hero status!
Sure to wear out his centre differential with all that power!

You offering me a rebuild?

Anytime that you are ready
viewtopic.php?f=6&t=31089&start=45