307 km/h with limiter!

[gorun]

My car has the M Drivers Pack where the limiter is raised to 280 km/h. My two previous tops speed runs both resulted in 286 km/h and the car wouldn't go past that. The other day I was able to pull 307 km/h and drove over 300 for about two minutes before running out of road. What do you think is the reason for these differences?

p.s. road was pretty similar in all runs

[artur777!]

dont forget about the discrepancies between speedometre speed and real road speed - it's technologically 5%

[SlammedR8]

and where did you do those speeds?

[ACZakka325i]

Originally Posted by slammedm3

and where did you do those speeds?

Likely Europe. I don't know where else you could do 180MPH for several minutes.

[gorun]

I would think that the speedo optimism is the 286-280 difference of 6 km/h that I have got on two occasions (286 indicated, supposedly 280 real). My car would stop to accelerate at precisely that speed twice, it was clearly a speed governor. Now the last time was different it didn't bounce off any limiter it just reached its top speed and the speed would change up and down between 307, 306 and 305.

p.s. could it be that I have done a heavy track day and passed the 10 000km mark before the last attempt? All runs were done on highway in Eastern Europe

[Atny286]

I am afraid your Speedo is a bit off... I have no limiter and hit 300kmh on the speedo while external GPS showed 285kmh (+15kmh, +5%), you seem to have a +27kmh (+9%)...

btw, I am sure it can do 300kmh GPS without the limiter (= 320-330 on the speedo), eventhough I never had enough 'free' road... (on the A31 North).

[Robin_NL]

Hi Anthony, yesterday I replied in the meeting section 'Dutch-Belgium'. Please read. Thanks.

[gorun]

Originally Posted by Atny286

I am afraid your Speedo is a bit off... I have no limiter and hit 300kmh on the speedo while external GPS showed 285kmh (+15kmh, +5%), you seem to have a +27kmh (+9%)...

btw, I am sure it can do 300kmh GPS without the limiter (= 320-330 on the speedo), eventhough I never had enough 'free' road... (on the A31 North).

No you got me wrong. All I'm sayin is that when I was doing 286 on the speedo I presume it was about 280 real. No way do I have 9% off.

[Atny286]

Understood. However, I think the 286kmh is not the 280kmh real, but the 305-307kmh is the real 280kmh in your case. As you say the car would not go passed 307 on the speedo, it means you have a limiter. The car would easily go 320kmh on the Speedo without a limiter. As I had 300 Speedo, it still had lots of power/acceleration, but other cars on the road caused me to slow down.

Normally I would expect +5-7% on the Speedo. So 280 limiter would get you to 295-300kmh on the speedo. If you get 307kmh on the Speedo with a 280 limiter, that is +9%. This is not really bad (as I have seen +10% in previous cars as well). You could try to fix a Garmin or Tomtom and see what gives you that. Those machines have highest speed memory, so no need to focus on GPS while doing Boeing-speeds...

Good luck!

Originally Posted by gorun

No you got me wrong. All I'm sayin is that when I was doing 286 on the speedo I presume it was about 280 real. No way do I have 9% off.

[thooooorgal]

have you changed your wheels / tyres ?

With the 19' : limiter = 275 (i do not have the 280 limiter option)
with the winter kit from BMW, 18', limiter = 285.

difference is due to a small difference in the size of the tyres.

BTW, if we take the same difference between the speed read on the tacho, and the top speed as per BMW

me With 19': BMW 250 / Tacho 275
You: BMW 280 / Tacho 307

same difference. You did not reach the limiter when your top speed was only 280+

[gorun]

Tyres and wheels are stock and I clearly hit the limiter on my two previous attemtpts at 286, however, it didnt kick in at my 307 effort, the car just didnt want to go any faster.

[Atny286]

Originally Posted by gorun

Tyres and wheels are stock and I clearly hit the limiter on my two previous attemtpts at 286, however, it didnt kick in at my 307 effort, the car just didnt want to go any faster.

What RON are you using? Whenever I go to Germany I use Shell's V-power Racing 100 (US equivalent 95-96), I have 19" stocks.
And try the GPS. Hopefully it does hit 280+ on GPS.

Good luck and have a nice flight!

[gorun]

I run the stock 19s with ps2 and 100 octane RON. I have a Tomtom, will give it a shot when I get a chance again. Is the Tomtom accurate when it comes to speed?

[Atny286]

Originally Posted by gorun

I run the stock 19s with ps2 and 100 octane RON. I have a Tomtom, will give it a shot when I get a chance again. Is the Tomtom accurate when it comes to speed?

TomTom will do. Let us know the outcome!

[footie]

Originally Posted by Atny286

Understood. However, I think the 286kmh is not the 280kmh real, but the 305-307kmh is the real 280kmh in your case. As you say the car would not go passed 307 on the speedo, it means you have a limiter. The car would easily go 320kmh on the Speedo without a limiter. As I had 300 Speedo, it still had lots of power/acceleration, but other cars on the road caused me to slow down.

Normally I would expect +5-7% on the Speedo. So 280 limiter would get you to 295-300kmh on the speedo. If you get 307kmh on the Speedo with a 280 limiter, that is +9%. This is not really bad (as I have seen +10% in previous cars as well). You could try to fix a Garmin or Tomtom and see what gives you that. Those machines have highest speed memory, so no need to focus on GPS while doing Boeing-speeds...

Good luck!

You are correct the norm is approximately 5% error on speedos and that would mean a 280km/h true speed would show a speedo reading of approximately 308km/h.

That is what I think is happening here.

The only thing I am less sure of is if 5% continues as speed increases, one would expect that at speeds of 80km/h the speedo would and should show 88km/h but I honestly would have though the difference would peak at 15km/h and hold that figure beyond the 150km/h point.