Top speed limiter info

[quality_sound]

So, a few days ago some douche in a Mustang felt the need to tailgate me, even as I changed lanes to let him pass, for about 10 miles. Not just staying behind me, but I literally could not see his headlights. I'm not sure what his problem was but I had had enough. I hit an unlimited section of the A63 and dropped the hammer. I'll give him props as he stayed with me to right around 135MPH. Since I was already there, and there was almost no traffic, I though about the question about the limiter and decided to see if it was there or not. I got up to 165MPH (indicated) and there were no signs it was going to stop any time soon but that pretty much gave me the answer.

Cliff's notes: US spec M3s delivered in Europe have no limiter, unless it's over 165MPH.

[kpneverdies]

I see that you live in germany.... i hope you didn't write this during the game of Germany VS. Australia FIFA world cup.

[quality_sound]

I'm American and I don't have live TV so I can't watch the matches anyway. Having said that, I wrote it during half time.

[Sleeper519]

Originally Posted by quality_sound

So, a few days ago some douche in a Mustang felt the need to tailgate me, even as I changed lanes to let him pass, for about 10 miles. Not just staying behind me, but I literally could not see his headlights. I'm not sure what his problem was but I had had enough. I hit an unlimited section of the A63 and dropped the hammer. I'll give him props as he stayed with me to right around 135MPH. Since I was already there, and there was almost no traffic, I though about the question about the limiter and decided to see if it was there or not. I got up to 165MPH (indicated) and there were no signs it was going to stop any time soon but that pretty much gave me the answer.

Cliff's notes: US spec M3s delivered in Europe have no limiter, unless it's over 165MPH.

Good for you for dusting off the D-B (I HAATE tailgaters), and for showing some initial restraint and courtesy by changing lanes. You're more patient than I would have been.

Regarding top speed limiters, I think i read that US spec M3s are set to 155 and Euro versions to 161. Remember, the speedo errors are about 2 mph at 40 mph, 4mph at 80, and so on. So 165 indicated would be about 155 actual.

But now that I think about that concept, wouldn't the limiter have to be based on the indicated speed (how can it know the true velocity? only the measured?). So I guess my logic doesn't hold...

[MysticBlue]

Electronically limited to 161. Speedometers read over, as has been discussed many times, and will most likely read 165 - 170 while true speed is limited to 161.

[blueman2]

Originally Posted by Sleeper519

...Remember, the speedo errors are about 2 mph at 40 mph, 4mph at 80, and so on. So 165 indicated would be about 155 actual.

I have noticed that my speedometer seems to be a bit high, but have never seen any threads on this subject. I will have to use my Garmin on the way home to do a real comparison.

Do all M3's have speedos that read 5% high? Or is the error + or - depending on the car? I have 19" stock wheels on mine.

[calintexas]

Originally Posted by blueman2

I have noticed that my speedometer seems to be a bit high, but have never seen any threads on this subject. I will have to use my Garmin on the way home to do a real comparison.

Do all M3's have speedos that read 5% high? Or is the error + or - depending on the car? I have 19" stock wheels on mine.

I've owned 3 BMW's, and the speedo has read fast in all 3. Garmin's are great. The speedometer feature is one of my favorites.

[Dntlvet]

Tailgaters need to be dusted. Wish I were back in Germany.

[smmmurf]

I hit the speed limiter on my 2009 M3 on European Delivery. It is definitely there in both 5th and 6th gears. I'd say it came on around 165 indicated.

[Sleeper519]

Originally Posted by MysticBlue

Electronically limited to 161. Speedometers read over, as has been discussed many times, and will most likely read 165 - 170 while true speed is limited to 161.

How does the car measure actual true velocity in order to limit it? GPS? Certainly not from the flawed speedo...

[kouhii]

Originally Posted by Sleeper519

How does the car measure actual true velocity in order to limit it? GPS? Certainly not from the flawed speedo...

I think it has to do with the conversion from kmph to mph where the accuracy is lost.

I am guessing the computer only uses 2 decimal places in order to improve the conversion speed.

[Chill72]

The car actually cuts off at 170 MPH indicated, I used my GPS and it shows 266 kph as actual top speed. I tested this on numerous ocassions.

[bobbyd1961]

i normally will slow down to a crawl to piss them off

[quality_sound]

Originally Posted by MysticBlue

Electronically limited to 161. Speedometers read over, as has been discussed many times, and will most likely read 165 - 170 while true speed is limited to 161.

I thought it was a straight 3MPH built-in error?

Originally Posted by bkm32008

Good for you Bro, I hate tailgaters. Did he flash his brights at you as well? Mustangs, BMW 335's, Audi, a tailgater is a tailgater.

Cheers

That's what pissed me off. He wasn't trying to get past me. Americans are targets already so lingering in the left lane is a bad idea to begin with so I'm not sure what his deal was. And this is something I just learned, flashing your highs is considered discourteous. To pass you turn on your left blinker. You'd only ever use your high in an inlimited section simply because they're visible from farther away.

Some useless trivia for the day.

Originally Posted by Chill72

The car actually cuts off at 170 MPH indicated, I used my GPS and it shows 266 kph as actual top speed. I tested this on numerous ocassions.

Really? I'll have to try that on a trip to the Ring or Hockenheim.

Originally Posted by bobbyd1961

i normally will slow down to a crawl to piss them off

Normally I would as well but you can get ticketed for driving too slow on the Autobahn. if we'd have been on a B-road or lower I'd have definitely been creepin'.

[BPMSport]

Speedo is roughly 5-8% off, especially at higher speeds. You could probably see 170 on the analog gauge before the limiter kicks in. Sometimes there are variations depending on the programming the car has - each car actually has four or five different speed limits built into the engine management control unit software. I've also seen some gear dependent variations as well.

And just for fun, a pic I took in the M3 a couple weeks ago- limiter removed of course

[MysticBlue]

Originally Posted by quality_sound

I thought it was a straight 3MPH built-in error?

No, it's a percentage. About 5% give or take, varies from car to car. This subject comes up every few weeks on this and every other forum, and is so full of conjecture and guessing and misinformation, even though it's been discussed a million times. I don't even have the patience to do it again. Search.

[quality_sound]

No, it's fine. I don't need a definitive answer. I was just hoping my experience would help figure this out since some have said euro delivered Ms have a limiter and some have said they don't. Apparently I wasn't driving fast enough to find out. Well, not yet anyway.

Mike - you're not helping, dude. I'm supposed to wait until I'm out of warranty to mod. Well, on this car a least. It would be a first for me.

[ideliver]

remember the speed limiter is just a "gentleman's agreement" between the automobile manufacturers...

[Race_Doc11]

Me too....

Originally Posted by bobbyd1961

i normally will slow down to a crawl to piss them off

[Chill72]

Originally Posted by quality_sound

I



Really? I'll have to try that on a trip to the Ring or Hockenheim.



N

I'm not sure you can reach top speed at the track, I wasn't able to do it at the ring. However if you ever drive to Spang and take that exit towards Bitburg...a nice straight opens up for about 4 km...easy to reach top speed there

[adc]

Originally Posted by smmmurf

I hit the speed limiter on my 2009 M3 on European Delivery. It is definitely there in both 5th and 6th gears. I'd say it came on around 165 indicated.

+1.

I've noticed that the speed limiter seems to come on differently at different times and in different driving scenarios - Mike@Powerchip seems to be onto something.

But it was always under 170mph indicated on the analog display.


I've heard many explanation as to why it would read high - here is what stuck in my mind. First of all, various tires will have various diameters, just check TireRack and you can easily see 0.2-0.3" variations. Even if that weren't the case, a tire may loose 8/32" during its life on the car, which means 16/32" = 0.5" diameter variation, which is a 2.7% diameter variation on the stock 18" rim. This doesn't even account for differences due to inflation pressures/temps.

So if you can easily have a 3-5% reduction in tire diameter due to brand, inflation pressure and wear, which would make the speedo read "higher" as the tire wears, then it's reasonable that the ECU has a 5% built-in margin.

Just saying...

[quality_sound]

Originally Posted by Chill72

I'm not sure you can reach top speed at the track, I wasn't able to do it at the ring. However if you ever drive to Spang and take that exit towards Bitburg...a nice straight opens up for about 4 km...easy to reach top speed there

Is that right... lol

Originally Posted by adc

+1.

I've noticed that the speed limiter seems to come on differently at different times and in different driving scenarios - Mike@Powerchip seems to be onto something.

But it was always under 170mph indicated on the analog display.


I've heard many explanation as to why it would read high - here is what stuck in my mind. First of all, various tires will have various diameters, just check TireRack and you can easily see 0.2-0.3" variations. Even if that weren't the case, a tire may loose 8/32" during its life on the car, which means 16/32" = 0.5" diameter variation, which is a 2.7% diameter variation on the stock 18" rim. This doesn't even account for differences due to inflation pressures/temps.

So if you can easily have a 3-5% reduction in tire diameter due to brand, inflation pressure and wear, which would make the speedo read "higher" as the tire wears, then it's reasonable that the ECU has a 5% built-in margin.

Just saying...

Oh believe me, I know all about overall diameter differences, even with "same sized" tires (15 years of driving WAY lowered VWs makes that important, but I'm on the OEM 19" Contis and they've only been on the car since early April since I was still on my winter set until then.

I'll find another unlimited section and give is go and see when it kicks in.

Thanks all.