07 touring speedo

<div class='quotetop'>QUOTE(Bill Merchant @ Mar 17 2007, 09:22 PM) [snapback]407677[/snapback]</div>

Bill<

will this work in a prius without nav??? my 06 package 5 doesn't have the nav system

 

<div class='quotetop'>QUOTE(Rangerdavid @ Jun 8 2007, 05:08 PM) [snapback]458365[/snapback]</div>

Even with the Navigation system, the calibration does not affect the speedometer, only the NAV distance calculations.

 

<div class='quotetop'>QUOTE(ken1784 @ Jun 7 2007, 08:32 PM) [snapback]457729[/snapback]</div>

OK. i will try to confirm that in my car tomorrow.
Another strange observation is that in the service menu the speed in miles/h is incremented in steps of 1, but the speed in km/h seems to be the calculated integer of the speed in miles/h, sometimes incrementing by 2 and sometimes incrementing by 1.
Is the system based on miles/h?

/e

 

<div class='quotetop'>QUOTE(Erik Sweden @ Jun 11 2007, 05:53 AM) [snapback]459256[/snapback]</div>

We observe something like...
39 -> 42 -> 44 -> 47 -> 50 -> 53 -> 56 -> 58 -> 61 -> 64 -> 67 -> 70 ...
so, it does not have relations to mph neither.

I don't think so.

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ Jun 10 2007, 11:58 PM) [snapback]459501[/snapback]</div>

Ok Now I have done a manual readout from Speedo, VehicleSignal_SPD and external GPS.
I have recorded the data from 0-170Km/h with data from at least every second speedo km/h step from 5-130 km/h. (will post the excel datasheet w. graphs later, right now I and excel aren't exactly friends )

Initially it is obvious that the "Speedo bias" is progressive in relation too speed, but it is not, as I first thought, in percentage, rather it is in steps.
Roughly from 3 - 30 km/h the bias is + 3 km/h, from 30-75 it's + 5 and from 75-up it's +8.

An interesting thing is that the the VehicleSignal_SPD is clearly not the source for the data to the speedo, this signal increments in steps of 2-3 km/h but the speedo increments (as we all know) in steps of 1.
So where is the data source for the speedo?


Will get back when I have made friends with Excel and done a deeper analyse.
/e

 

<div class='quotetop'>QUOTE(Erik Sweden @ Jun 12 2007, 05:20 PM) [snapback]460433[/snapback]</div>

Here is the Data, Chart and my test setup.
/e

 

Since the car is designed and built in Japan, I believe that all internal readings are in metric. Speed is KM/H, temp in C, etc. Then the system converts to english.
This is certainly evident with the ambient temperature display.
But then, as pointed out, the english speed readings are in increments of 1, so the car may be calibrated in english units internally and converted back to metric for the US (or NA for that matter) cars.

But all the readings are being sensed off the braking system's wheel speed sensor. The NAV takes that same pulse drive from the wheels which is routed through the combination meter (which includes the speedometer). The NAV does dynamically adjust the registered speed/distance since it does have an independent reference: GPS. The GPS may have an error of say 300 feet, but over miles of travel, especially in one direction, that error is a fixed amount, which as the measured distance increases, the percent error goes down. For example, if I travel from Tampa to NYC, it is about 1000 miles. The GPS would calculate that very accurately, with possibly an error of 300 feet at either end of the trip, for a total possible error of 600 feet. A mile is 5280 feet, so the trip would be about 5.2 million feet. 600 feet seems insignificant compared to that!
This error correction that the nav uses is not fed back to the combination meter.

Now why would the speedometer be biased to show a higher than true reading but never lower?
So that for safety, you are always travelling slower than you think you are. If the speed limit says 60, and you are one to follow the speed limit, you'll never exceed that limit due to speedometer calibration. And so, you can almost never use the excuse that the speedometer was wrong.
Law enforcement though would have to be careful about clocking you by following you and your speed and then looking at their speed. They could be reading higher than actual.

 

I tested my 07 Touring speedometer against my Garmin eMap GPS this morning.

The Prius speedo is dead on. The eMap shows one decimal place (e.g. 48.5 mph), and the Prius generally would round up to 49.

I compared at all speeds up to around 60mph. Didn't go beyond that.

 

<div class='quotetop'>QUOTE(andrewsilver @ Jun 15 2007, 10:27 AM) [snapback]462317[/snapback]</div>

Then it seems that the previous poster was correct, the US Prii are correct and the European are biased.
Why? I risk being political, but Europe is probably more inclined to follow UN directives than the US. (see previous posts)

Ok, never mind, does somebody know how to "unbias" the speedo?

/e

 

bump

Methinks the south-pacific model also has the 'improved safety' speedometer (although I had seen odometer funny-readings too); and I too would thus be interested in 'fixing' this little feature. I like to know that 50kmph on the numbers afore me is fifty kilometres per hour on the ground.
(That way I know precisely how much I'm speeding!)

I will try the Service Menu speed reading at some stage and see how that correlates.

Does the built-in Nav offer a speed indicator derived just from GPS (buried in a service menu, etc); or are you all using third-party GPS to check your speed?