S2 won't go faster than 265 km/h

[S2central.net]

A 200bhp 80 Avant doing 260kph = ********
It is just not physically possible - I'll bet the speedo is way off on that. It should be struggling to hit 150mph (238kph - so a 10% error easily explains that)

[S2central.net]

That 80 Avant - for the record - if it is quattro then it will struggle to make 150mph... but obviously drivetrain losses will be lower if she is FWD - however... Needs to be down in very low 5% territory for 260kph - I still say the speedo is reading high on this.

[driftin jo]

ow well I may be a little upset in this

I have a couple of friends with some fast cars that reach 260+ quite easy with less hp. There is one with 80 Avant 2.8 30V with about 200 hp, another with a 325 E36 coupe they both do 260 km/h and there is one with a E36 M3 286 hp. that does 280+

It's not that hard to see how fast your going at that speed but in this case I had a camera attached to my steering wheel.

And then they all woke up and had their cornflakes

[quattro84]

@ S2central: Rho gives the density of the air. You are driving through air and not yorkshire pudding, indian curry, or pure helium.

Another rather big aspect in therms of losses is the rolling resistance, Fr~m*g*mu, with m being mass in kg, g the gravitational acceleration, and mu surface roughness. It is speed dependant.
Hysteresis in the tires are what make these losses and are quite obviously noticable when you touch the tires after a run on the freeway . Another aspect of losses is acceleration, and last is driving up a light slope. Bearing losses are in the drivetrain losses.

At 265km/h (~74m/s) makes 158kW which is about 215Hp, rolling resistance is good for another 15-20hp, so 235 at the wheels makes 282hp at the crank with a factor 1,2 for drivetrain losses.

[S2central.net]

Yes - I understand 'rho' well enough... threw me at first though... I agree with your calcs above - I made it 19bhp rolling resistance and ~280bhp total estimate.
Good thread - applied physics - but why they never made it this interesting when I was a teenager at school I shall never know.

[quattrostyle]

A 200bhp 80 Avant doing 260kph = ********
It is just not physically possible - I'll bet the speedo is way off on that. It should be struggling to hit 150mph (238kph - so a 10% error easily explains that)

well 'she' is a FWD and I bet it will have 10% error or so, but it's coilovered and has RS2 bumpers and wing mirrors maybe that helps a little bit

@driftin jo I never seen one of them eat cornflakes, will ask if they do though.

[quattrostyle]

well they don't eat cornflakes.

Will do a run next week with GPS.

[Ross]

I would suggest you get them all to do a GPS run as well for comparison... I had my coupe at 165mph, it probably had another 5mph in it as it was a very slight gradient. That was on H+R/Bilstein at the time, don't know the power but it was most likely 300hp at the time, give or take a few pence, so similar to yours...

[quattrostyle]

I guess dropping the car slightly would improve top speed a little bit. We will do a test drive with the 3 of us at the same time (if traffic allows us)

[Quattro Ayes]

Am I the only one noticing that the km doesn't move a bit? Maybe something is wrong with your speedometer.?

[quattrostyle]

Yeah I know km. counter works now and then, speedo is working okay as always.