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E85 / E86 Z4 (2003-2008)
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  #1  
Old 09-08-2007, 04:14 PM
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Z4-M speedo check

Indicated----Actual

40-----------38.2---1.8
45-----------42.9---2.1
50-----------47.6---2.4
55-----------52.3---2.7
60-----------56.8---3.2
65-----------62.2---2.8
70-----------67.0---3.0
75-----------71.9---3.1
80-----------76.5---3.5

Will move the needle soon.
Will also be adding a white Coupe on the tach like I did with the Z3 but in the top area.




Last edited by Ron Stygar; 09-08-2007 at 04:17 PM.
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  #2  
Old 09-08-2007, 05:10 PM
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So how did you verify the speedometer's "accuracy"?
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  #3  
Old 09-08-2007, 06:22 PM
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So how did you verify the speedometer's "accuracy"?
Garmin Etrex.

Last edited by Ron Stygar; 09-09-2007 at 06:10 PM.
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  #4  
Old 09-09-2007, 07:04 AM
Caddyshk Caddyshk is offline
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So ~ 4.5% speedo error - thats basically what I found too.
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  #5  
Old 09-09-2007, 07:11 AM
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Many manufacturers will build-in a speedo error indicating a higher than actual speed. Think of the consequences of having a lower that actual speed indicated, especially if you change wheels and tires tant have a greater circumference than stock.
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  #6  
Old 09-09-2007, 01:07 PM
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Originally Posted by GeorgeT View Post
Many manufacturers will build-in a speedo error indicating a higher than actual speed. Think of the consequences of having a lower that actual speed indicated, especially if you change wheels and tires tant have a greater circumference than stock.
-I've read that this has to do with legal consequences of producing a speedo that underreads. If I remember correctly, a speedo can be up to -1 to +5mph off without incurring a fine or recall. But the penalty for exceeding the -1mph is much more severe so most manufacturers aim for +4mph. I wish I could remember where I read all this.
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  #7  
Old 09-09-2007, 01:16 PM
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Originally Posted by Palantirion View Post
-I've read that this has to do with legal consequences of producing a speedo that underreads. If I remember correctly, a speedo can be up to -1 to +5mph off without incurring a fine or recall. But the penalty for exceeding the -1mph is much more severe so most manufacturers aim for +4mph. I wish I could remember where I read all this.
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  #8  
Old 09-09-2007, 02:09 PM
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-Much better. Thanks Ron
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  #9  
Old 09-09-2007, 02:46 PM
BMcCoupe BMcCoupe is offline
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Quote:
Originally Posted by Ron Stygar View Post
Indicated----Actual

40-----------38.2---1.8
45-----------42.9---2.1
50-----------47.6---2.4
55-----------52.3---2.7
60-----------56.8---3.2
65-----------62.2---2.8
70-----------67.0---3.0
75-----------71.9---3.1
80-----------76.5---3.5

Will move the needle soon.
Will also be adding a white Coupe on the tach like I did with the Z3 but in the top area.
how will you be moving the needle? is this something that can be done in the MZ3 too? or just MZ4?
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  #10  
Old 09-09-2007, 03:17 PM
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Quote:
Originally Posted by BMcCoupe View Post
how will you be moving the needle? is this something that can be done in the MZ3 too? or just MZ4?
http://bimmerfest.com/forums/showthread.php?t=4925

Actually easier on the Z3 if you have a signal/counter device.
You feed a signal into the wiring from the differential sensor.

The Z4 gets it's speed fron the rear right side wheel ABS sensor.
Haven't looked into that yet so maybe the Z4 can be done the Z3 way too.
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  #11  
Old 09-09-2007, 03:19 PM
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Quote:
Originally Posted by BMcCoupe View Post
how will you be moving the needle? is this something that can be done in the MZ3 too? or just MZ4?
Feed a signal into the speed sensor wire and move the needle to the correct location. Same thing on the Z3, search here from when Ron did it on his '01. Need a signal generator to do it.
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  #12  
Old 09-09-2007, 03:22 PM
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Quote:
Originally Posted by Ron Stygar View Post
http://bimmerfest.com/forums/showthread.php?t=4925

Actually easier on the Z3 if you have a signal/counter device.
You feed a signal into the wiring from the differential sensor.

The Z4 gets it's speed fron the rear right side wheel ABS sensor.
Haven't looked into that yet so maybe the Z4 can be done the Z3 way too.
No seperate speed signal on the Z4? Makes sense, but I hope it doesn't complicate speedo calibration for you. I forget the frequency of the signal from the wheel speed sensors, but somewhere I have a scope trace from one.
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  #13  
Old 09-09-2007, 03:33 PM
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Originally Posted by dwm View Post
No seperate speed signal on the Z4? Makes sense, but I hope it doesn't complicate speedo calibration for you. I forget the frequency of the signal from the wheel speed sensors, but somewhere I have a scope trace from one.
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  #14  
Old 09-09-2007, 04:44 PM
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Quote:
Originally Posted by Ron Stygar View Post
Indicated----Actual

40-----------38.2---1.8
45-----------42.9---2.1
50-----------47.6---2.4
55-----------52.3---2.7
60-----------56.8---3.2
65-----------62.2---2.8
70-----------67.0---3.0
75-----------71.9---3.1
80-----------76.5---3.5

Will move the needle soon.
Will also be adding a white Coupe on the tach like I did with the Z3 but in the top area.



Looks like about a 4% or less speedo error all the way through, which isn't that bad. What was your GPS accuracy reading while you did this?
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  #15  
Old 09-09-2007, 04:58 PM
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Originally Posted by Dammmittt View Post
What was your GPS accuracy reading while you did this?
Have no idea. Had at least four satelites.
Worked with the Z3 when compared to the frequency and OBC.
On the Z3, the OBC displayed the actual speed.
The Z4 OBC matches the speedometer. Will be looking at that too.
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  #16  
Old 09-09-2007, 10:20 PM
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When I started using a Nuvi 660 I discovered my speedometer didn't agree with the GPS either.

My tests show almost the exact readings Ron got when I compared the Etrex and Nuvi 660 to the Speedo readings.

I also ran some tests on a couple of "measured" test sections on the highway to see if the GPS units were believable. One of my routes takes me through a measured 5 mile test section so I was able to get quite a few runs without interference of traffic so the tests were constant speed. Both GPS units and my stop watch agree very well. The speedometer error is easily measurable in a measured mile.

Since the Etrex and Nuvi say the same thing and they agree with my timed tests I trust them.
Now I use the Nuvi 660 as my speedometer since it has a big display which is easier to see anyway.

I created a chart and took it to the dealer and they were at least knowledgeable enough (this time) to point me to the documents Ron pointed out and said they wouldn't do anything with my ~3 mph overage. These values are well within the acceptable limits.
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  #17  
Old 09-10-2007, 01:21 AM
MysticBlue MysticBlue is offline
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My Escort 9500 is consistent with what you folks have seen. GPS speed measurment is very accurate; ironicly, more accurate than actual position.
I also get about a 4% difference.
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  #18  
Old 09-10-2007, 09:40 AM
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thanks for the info guys

so when i had an indicated 270km/h i was just going 260km/h
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  #19  
Old 09-10-2007, 10:04 AM
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Anyone have the deltas from 90 - 155? Ron's data trends slightly upwards with speed, so I wonder what the curve looks like to the limit.
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  #20  
Old 09-10-2007, 09:31 PM
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Originally Posted by Zuzax View Post
Anyone have the deltas from 90 - 155? Ron's data trends slightly upwards with speed, so I wonder what the curve looks like to the limit.
When I ran at the electronic limit for a couple minutes the speedometer looked like ~157 but the GPS said the max speed was 150. I think I was at the limit although I didn't feel any change in the way the engine ran. The car just wouldn't go any faster.

I don't have any other readings between 90 and 150.
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  #21  
Old 09-11-2007, 04:43 AM
Caddyshk Caddyshk is offline
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The percentage of error should remain constant unless there's calibration error in the speedo dial itself. Without a digital readout, Ron was eyeballing his speed, thats why his % of error varies. Take the mean of all his measurements and assume a baseline %.
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  #22  
Old 09-11-2007, 08:30 AM
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Originally Posted by Caddyshk View Post
The percentage of error should remain constant unless there's calibration error in the speedo dial itself. Without a digital readout, Ron was eyeballing his speed, thats why his % of error varies. Take the mean of all his measurements and assume a baseline %.
Eyeballing via cruise control.
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  #23  
Old 09-11-2007, 08:34 AM
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Quote:
Originally Posted by sig_int View Post
When I started using a Nuvi 660 I discovered my speedometer didn't agree with the GPS either.

My tests show almost the exact readings Ron got when I compared the Etrex and Nuvi 660 to the Speedo readings.

I also ran some tests on a couple of "measured" test sections on the highway to see if the GPS units were believable. One of my routes takes me through a measured 5 mile test section so I was able to get quite a few runs without interference of traffic so the tests were constant speed. Both GPS units and my stop watch agree very well. The speedometer error is easily measurable in a measured mile.

Since the Etrex and Nuvi say the same thing and they agree with my timed tests I trust them.
Now I use the Nuvi 660 as my speedometer since it has a big display which is easier to see anyway.

I created a chart and took it to the dealer and they were at least knowledgeable enough (this time) to point me to the documents Ron pointed out and said they wouldn't do anything with my ~3 mph overage. These values are well within the acceptable limits.
I'd definately match the GPS readings next to a flat measured area of road with a stopwatch. Seems like the most fool proof way to get an accurate reading. Hope the cruise control works well
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  #24  
Old 09-11-2007, 08:35 AM
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thanks for the info guys

so when i had an indicated 270km/h i was just going 260km/h
I've had an indicated 270 km/h as well, never took the time or effort to verify it
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  #25  
Old 09-16-2007, 08:34 AM
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where is the best place to calibrate my speedometer legally I got a couple of tickets this week and I think doing so would probably help me in court.
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