[SCCThree]

Originally Posted by 3.0L

This ^^^

The speedometer in my M235i consistently reads about 2 miles per hour on the optimistic side when compared to those roadside radar signs. Consistently.

My question is: does it just show a couple extra MPH on the speedo but the computer has accurate MPH? Dunno...

[3.0L]

Originally Posted by SCCThree

My question is: does it just show a couple extra MPH on the speedo but the computer has accurate MPH? Dunno...

I think it's reasonable to assume that the speedometer gets its info from the computer. In any case, the roadside radar readouts consistently prove that my speedometer is off.

Next time out, I'll try to remember to do a timed run between mile markers. One mile traveled at 60 MPH indicated should take exactly 60 seconds. Probably set the cruise control to 60, first.

And for what it's worth, every car I've owned during the past 20+ years has had an optimistic speedometer, including my current MB GLK-350.

[Viffermike]

Originally Posted by 3.0L

I think it's reasonable to assume that the speedometer gets its info from the computer. In any case, the roadside radar readouts consistently prove that my speedometer is off.

Next time out, I'll try to remember to do a timed run between mile markers. One mile traveled at 60 MPH indicated should take exactly 60 seconds. Probably set the cruise control to 60, first.

And for what it's worth, every car I've owned during the past 20+ years has had an optimistic speedometer, including my current MB GLK-350.

This is actually an unofficial mandate by the Feds that goes back to the 55 MPH days in the 1970s. Car manufacturers calibrate speedometers to read slow for two primary reasons:
1). To account for the loss in rolling diameter as a tire's tread wears (lower rolling diameter = faster RPM = higher speedometer reading)
2). To prevent lawsuits and such against car manufacturers, municipalities, states, etc. for false speed readings that lead to unlawful behavior, i.e. speeding tickets

Most U.S. law enforcement agencies are instructed to NOT pull over vehicles that are traveling less than 10 percent over the posted speed limit. Why? A combination of three reasons:
1). User error/improper calibration of speed-reading apparati (timers, laser/radar, etc.)
2). The aforementioned speedometer calibration tendencies
3). The relatively low income that comes from most low-level speeding tickets (i.e., below 10 MPH, not in a construction zone, etc.), and the likelihood that income will be mitigated by defendant challenge in court. In other words, it's simply not cost effective.

Most modern cars' gauges are computer controlled, so what the OBDII says (and what the digital readout would say if it's coded) is almost certainly going to mirror what the analog gauge says. That's definitely the case with the speedometer on my P3Cars gauge, which is an OBDII device.

And now y'all know.

[BEM-S4]

Not sure if it's a "mandate" but in PA at least you really have to be cooking to get a real ticket. I got pulled over doing 95 in a 70 and they wrote me for the highest possible speed for the lowest possible infraction - believe it was 79. Logic being you get no points, pay a fine, and it's not worth your time to fight it. I am sure someone did some major statistical analysis along the lines of $100 no points collect 95% of the time, $300 + points collect 25% of the time, so EV of smaller tickets higher.

[Viffermike]

Precisely. So basically you can travel 77 MPH in a 70 MPH zone and be golden; a cop won't touch you unless you're doing something in addition to the speed (i.e., weaving, taillight blown out, what have you).

[BEM-S4]

Originally Posted by Viffermike

Precisely. So basically you can travel 77 MPH in a 70 MPH zone and be golden; a cop won't touch you unless you're doing something in addition to the speed (i.e., weaving, taillight blown out, what have you).

They did keep me sitting at the side of the road for half an hour and yelled at me for laughing the whole time. The cop apparently didn't find the humor in the absurdity of a 36 year old getting pulled over for "joy riding" in a station wagon with temp tags that belonged to my father. Also was not amused when I told him I had no choice but to test the car properly, that I just had Dinan Stage 1 installed and needed to make sure it was working properly before I returned the car to dad. You know, for safety purposes.

[Viffermike]

Originally Posted by BEM-S4

They did keep me sitting at the side of the road for half an hour and yelled at me for laughing the whole time. The cop apparently didn't find the humor in the absurdity of a 36 year old getting pulled over for "joy riding" in a station wagon with temp tags that belonged to my father. Also was not amused when I told him I had no choice but to test the car properly, that I just had Dinan Stage 1 installed and needed to make sure it was working properly before I returned the car to dad. You know, for safety purposes.

[Gabrola]

Originally Posted by Viffermike

Most modern cars' gauges are computer controlled, so what the OBDII says (and what the digital readout would say if it's coded) is almost certainly going to mirror what the analog gauge says. That's definitely the case with the speedometer on my P3Cars gauge, which is an OBDII device.

My experience is actually exactly the opposite. My OBD reading through Torque reads consistently lower than my speedo. Today I set my cruise control to 100kph and Torque was reading 93kph which was the same exact speed indicated by GPS.
This actually makes sense since the OBD reads the value directly from the wheel speed sensor while the speed correction happens at the instrument cluster (and can be coded off by coding KOMBI).

[Maynard]

I'd heard that BMW set their speedos low, didn't realize it was across the industry, so neat trivia. Gabrola's info is in line with my expectations - I would assume that the gauge is biased, but that they have reliable accurate info for the computer to use to calculate MPG etc. (or it would also be 10% off).

[martopoulos]

App-based 0-60 times are widely inaccurate-- the GPS hardware is just not meant for something like this. Someone on this forum also claimed their m235i with a few mods was getting 3.6 seconds when measured with an app. Keep dreaming. If you want to know your time, go to a track or get a real accelerometer. Here's one that has been consistently accurate (i.e. before mods it consistently registered 4.6 seconds, and after Dinan mods is consistently showing 4.3 - 4.4):

K.A.T. Matrix 3-Axis Car Performance Accelerometer - ~$110 on Amazon, though out of stock at the moment

[Fasteddy1]

Originally Posted by martopoulos

App-based 0-60 times are widely inaccurate-- the GPS hardware is just not meant for something like this. Someone on this forum also claimed their m235i with a few mods was getting 3.6 seconds when measured with an app. Keep dreaming. If you want to know your time, go to a track or get a real accelerometer. Here's one that has been consistently accurate (i.e. before mods it consistently registered 4.6 seconds, and after Dinan mods is consistently showing 4.3 - 4.4):

K.A.T. Matrix 3-Axis Car Performance Accelerometer - ~$110 on Amazon, though out of stock at the moment

The BMW laptimer app does not use GPS.

[BPAC306]

Guys... I did 12.3 in the 1/4 stock.... My 1/8 mile time equates to about 3.8-3.7 0-60 my time slip is posted in the forum.....

[crbalch]

Get a VBOX Sport and then report back. I have an extremely hard time believing this.

[BPAC306]

Originally Posted by crbalch

Get a VBOX Sport and then report back. I have an extremely hard time believing this.

But why....

http://www.2addicts.com/forums/showthread.php?t=1317455

[Viffermike]

Originally Posted by Gabrola

My experience is actually exactly the opposite. My OBD reading through Torque reads consistently lower than my speedo. Today I set my cruise control to 100kph and Torque was reading 93kph which was the same exact speed indicated by GPS.
This actually makes sense since the OBD reads the value directly from the wheel speed sensor while the speed correction happens at the instrument cluster (and can be coded off by coding KOMBI).

Interesting. I didn't realize that. I'll have to re-examine the P3Cars reading vs. the speedometer; I haven't compared for a good year and a half, and my tires are worn (rears are below 4/32; getting PSSs all around as soon as Mr. Tax Man sends my refund along)

Would the digital speedo that can be coded for the center cluster display match the analog speedo or the OBDII data?

[Gabrola]

Originally Posted by Viffermike

Interesting. I didn't realize that. I'll have to re-examine the P3Cars reading vs. the speedometer; I haven't compared for a good year and a half, and my tires are worn (rears are below 4/32; getting PSSs all around as soon as Mr. Tax Man sends my refund along)

Would the digital speedo that can be coded for the center cluster display match the analog speedo or the OBDII data?

I have that coded on my car and it matches the analog speedo.

[crbalch]

Originally Posted by BPAC306

But why....

http://www.2addicts.com/forums/showthread.php?t=1317455

Using an app on winter tires vs actual timing on what I can assume are summer tires. That's why.

[BPAC306]

Originally Posted by crbalch

Using an app on winter tires vs actual timing on what I can assume are summer tires. That's why.

Regardless of what tire you have or any timing.... the track does not lie
and the vehicle is consistent (remember its stock), my best run and 60 foot - 1/8 mile were achieved about 5 runs in (getting used to launch control)

Did you click on the link and look at my time slip?

[crbalch]

Originally Posted by BPAC306

Regardless of what tire you have or any timing.... the track does not lie
and the vehicle is consistent (remember its stock), my best run and 60 foot - 1/8 mile were achieved about 5 runs in (getting used to launch control)

Did you click on the link and look at my time slip?

Yes I did...and I agree that your result is impressive. I wasn't questioning you at all, I was questioning the OP's result.

[rich8566]

Originally Posted by Joe240

I'm not doubting the rubber. I launched with my 240 on the DWS06 and had zero tire spin. Granted I'm on 235/265 so I'm sure it's a significant difference than his snow tires, but the xDrive system is quite amazing with putting the power down.

What I'm doubting is the 3.8 Seconds only because an app is never 100% accurate when it's relying solely on GPS coordinates and the algorithms because the gps is accurate to say 100ft or something like that. That means that it could easily be a difference of .2 seconds or more and it also depends on the signal strength (remember gps on a phone is based on towers, not satellite).

I'd be much less skeptical if this was through OBDII connection and monitoring like through JB4 or something, or maybe if it was trap speeds at a drag strip because those are using more accurate sensors (speedometer reading through OBDII or set distance and measuring time between 2 specific points).

I'm not trying to knock on your time OP, I'm just trying to be a little more reasonable about what could influence that time. I have a xDrive 240 and I want it to do 3.8 stock so bad, but I just don't feel it's there. Even knowing that the xDrive is putting 308whp down with just below freezing temps (my insoric dyno run).

JB4, I could definitely see pushing closer to 4seconds for sure. Other mods on top definitely hitting 3.8

I once had a mobile gps record and stored an indicated speed of 175 mph which was clearly way above the top speed of the vehicle it was used in.

[rich8566]

Originally Posted by Fasteddy1

[IMG]http://i18.photobucket.com/albums/b1...pskggmmnpj.jpg[/IMG]

Completely stock except for an M2 Exhaust. I don't know that the exhaust gains it any power at all though.

This is in the winter, 30 degrees outside on snow tires.

I have to say I am pretty impressed.

Pat

Impressive. Don't listen to others here who discredit this result. It is what it is so take it for what it's worth.

[rich8566]

Originally Posted by Fasteddy1

One other thing to note is that BMW speedometers are known to read high. So a 0-60 run is likely only a 0-58 run....

Pat

I concur that BMW speedometers are off by about 3-5% which is 2-3 mph at most normal road and highway speeds. This is true for each of the 5 BMWs that I've had since 2007.