Vag-Com Dynoplot

[Doug_RS2]

It doesn't look very smooth - but vag-com only logs data every 0.6s on my laptop.

I assumed a weight of 1500kilos for the car.

It uses the dynoplot.xls available from Ross-Tech - it should take into account losses as it measures those on slowing down - so is at the flywheel.

[Mihnea]

Any 1/4 mile times Doug? The ABY coupe's weight is about 1525kg from the factory, now if you have deleted the AC maybe it's a bit less...

Any comparison points with some other cars, for instance a stock S2 or something like that?

Cheers,

Mihnea

[Mihnea]

466.5lb/ft=634.4 Nm, not bad although it comes on late...

What about figures at the wheels? Can you do this? More work for you mate now that you got us started with this

[Greg_S]

when you stop by my dads we can weigh the cars to see how much they actually weigh.

Thats a very powerful motor you have there doug!

Greg

[Mihnea]

Awesome figures!!!


Now where's Doug gone? I betcha he went to have a few drinks to celebrate these figures

[Mihnea]

@Paul N, what about doing the same on your car BTW so we know about how far off these readings are? I'd suspect them to be pretty accurate actually, especially knowing that this is what most of the dynos do nowadays...

Cheers,

Mihnea

[ADU_S2]

excellent figures doug, good on ya

i bet ur happy with these figures mate.

[marks2]

is this car running at 470 bhp ?

i dont know much about how u derive hp, what is meant by hp at the wheel.

sorry to sound like a total plum but u learn something every day right (ive got alot to learn

so a stock rs2 engine runs at 315 bhp so is this at the wheel, and so doug if your car is running at 475 bhp that is a total monster!!!

[Doug_RS2]

I'm not sure what figures I am supposed to use in the "Decel Time Stamp" column - this must be a cut and paste of the car slowing down but I can't see how it goes in that column - I assume that works out losses on the car and so you get a powe at the flywheel.

How do I work out power at the wheels?

I am sort of happy - it needs more of a kick. I think the figures are high - It definitely has more power than Sals - and his was 395bhp but my peak figures are a bit too high - I think. I was positive I revved to the rev limit but there seems to be a delay on the logs.

I'll try and get a 1/4 mile time worked out - and a boost curve.

[Mihnea]

@Doug: what gear did you do the run in?

[audiman]

Doug, v. nice mate!! Mihnea just emailed me that picture!!! F**king hell man, i want mine running now!! Im up for a bit of that 475bhp!!! LOL. Race on. See you on track mate

[Doug_RS2]

4th gear boost profile

[Mark Halligan]

Great figures Doug

Mark.

[S2 Ant]

Doug those figures look awesome!!! And you want more?!?!!?

[S2central.net]

I shall definitely have to try this on standard and chipped trim on mine. I'm really hacked off that I hadn't thought of this application sooner - I'm assuming that Ross-Tech has just developed a tool based on the time and speed info from log files.

Trouble is I'd need to get back to 1st principles on this 'butt dyno' stuff to start making some sense of the numbers. I tried to remember some applied mathematics equations early this morning and arrived at some vague ideas how we might do this.

My simple theory (ignoring losses for transmission, aerodynamics, noise, heat and whatever else) is that the energy 'E' required to accelerate a car (of mass 'm') from initial speed (u) to final speed (v) over a period of time (t) can determine the power of the engine. This assumes one of Newtons laws that you can't get energy from nothing ie - it is the energy provided by the turning of the wheels which moves the car forward over time.

That means Energy expended, E = Kinetic energy at speed 'v' minus kinetic energy at speed 'u'

E = mv^2 - mu^2

Knowing that Energy equates to the power delivered over time we have :

Power, at wheels = Energy / Time

and assuming 25% quattro drivetrain loss we have:

Power, at flywheel = (Power at wheels)/0.75

Does this fly with the proper engineers out there? I'm winging it really but I have this thing about first principles at the minute to the point that all of this discussion is meaningless until we can understand the basic maths.

I hope I have this the right way round - otherwise power runs in 3rd gear would give much different values than 4th gear.

The calculation *must* be derived purely from speed, time and weight info - perhaps in a more correct fashion than my rough attempt here. The G-meter products must do this in hardware as the only device they have for measurement is an accelerometer and time (which derives speed from v = u + at). The G-meter operator inputs weight for the device to complete an approximate power calculation.

Of course once we have power, we can calculate torque.

Am I mental ?


Paul