Speedo/odo calibrated for OE tire size?

I'm just saying "We have the technology. We can make it better".
We could have Accuracy !!
Who doesn't like Accuracy??

The GPS re-calibration would be/could be a procedure that is done in the background once a month during a long drive where both speedo and GPS differences have been consistent for X minutes/miles.

But if everyone, and the manufacturers, thinks this is "Too hard to do" or "Not worth the effort",,,,
we can continue to live with Inaccuracies ,, "in this day and age".

 

If it is going to drive up the cost to be accurate then I am happy with the planned inaccuracy. It's really not a big deal IMO.

 

As we say in the Biz,,, "It's just software"...

Assign 10 young Toyota nerds to make speedo/odo/fuel consuption info accurate.

It's not Rocket Surgery.

To me, it is a Big Deal that I have to add a correction factor to every last bit of data my car displays to me.

I don't think it's "planned", I think it falls under the "Good Enough" category.

It's unacceptable,,, "In this day and age"...

Oh well,, maybe some day.....

 

I have Japanese make Prius C (Called Toyota Aqua). I don't think so there is so much error deliberately in-cooperated in speed. As i have been fined @136Km/h and my actual speed on Meter was 137Km/h. there is no much difference.

 

Different markets have different deliberate errors, depending on legal standards and normal industry practice. E.g. European markets typically have larger offsets than than the North American market. I don't know where Japanese-domestic-market cars fall. Japan is a signatory to the same agreement used in the EU, but that doesn't preclude having near zero error.

At least here, speeds marked on traffic citations are not a good reference to calibrate odometers, though stories suggest that officers here often seem to round down, not mark up. Plus, if your speed is varying, you don't know just when that officer tagged your speed.

For a better reference, use a GPS unit instead.

 

Agree with you "if speed is varying, you can't know just when that officer tagged speed". Need better arrangement to cross check ODO meter speed.

 

I missed this thread back in the day. The combination meter (speedo / odo) gets its information from a pulse train that is generated by the brake/skid ECU (which, in turn, is getting its information from the four wheel sensors).

And the brake/skid ECU is loaded with different firmware for factory 15" and factory 17" cars (see, for example, T-SB-0363-10).

 

FWIW, when we alternate between 195/65R15 snow tires and 215/45R17 OEM size, I don't see a noticeable difference. I've looked back-and-forth between speedo and Garmin, and they're always within 1~2 kmh of each other, any time of year.

I appreciate technically the 17's are slightly smaller OD, but it seems like it gets lost in the noise.

 

Just about any GPS unit should be able to help cross-check. I have an old hiking unit, newer automotive unit, and now a smart phone with GPS apps. Each of them is sufficient.

 

got two apps, DigiHUD Speedometer & Ulysse Speedometer , will check them

 

Checked the speed with Ulysse Speedometer, there is a difference of 8km/h , on Car meter it was 124km/h but on Ulysse Speedometer it was 116km/h

 

That is a 7% error. It seems high for a North American market car, but very much in line with some reports we have had for European market cars, where the allowance is at least 10%..

 

Its Japanese market CAR, Right hand drive imported from Japan

 

I don't recall seeing speedometer error reports from Japan, so don't have any idea what their typical errors are. My only hint is that Japan has adopted the same market regulation for this that most European nations have adopted.

 

Same situation as you. Drove it on a 1000 km stretch between provinces and noticed an exact 7 km/h variance on my Japanese import. It can't be fixed though, so gotta learn to live with it.

The worst part about this is that the EV battery cuts off far sooner than it should, as the speedo may show 45 km/h when I'm actually going 38 km/h. Really annoying!

 

Was that variance on the odometer or speedometer?

 

Speedo. My speedo would show 87 km/h whereas two apps running on two of my phones would both show 80 km/h. I figured the app was more accurate.

 

Yes, the GPS apps ought to be accurate.

Auto industry standards, written long before GPS apps or digital speedometers, forced the old analog speedometers to be biased high. They had much poorer measurement accuracy then, and a significant bell curve error distribution. Rules and laws did not allow the units on the low end of the curve to read slower than true speed. To achieve this, the center of the bell curve must read significantly higher than true speed.

Today's digital measurements produce much narrower bell curves, but the industry norms haven't caught up.

 

The odometer should currently be fairly accurate. Just my 2 cents: that's WAY more important than accurate speedo. To get the speedo accurate you need to throw everything else off.

If you're aware of the speedo error, you can adjust your speed accordingly. If it's absolutely imperative to you to to never drive slower than the posted speed limit. For example.

 

In the U.S., putting the same common speedometer error (or bias) into an odometer is considered warranty fraud. Several lawyers got rich on lawsuits about this.

If you have an OBDII-port engine monitor (ScanGauge-II, or Torque app with Bluetooth dongle, or many other choices), it can display the speed that the car's internal computers are using. In North America, this internal computer speed is fairly accurate, and does not have the same error or bias as the Speedometer display. I.e. the speed error is added right into the speed display, and is not present elsewhere in the electronic controls.

I don't recall if drivers in other markets have made similar observations, but it is worth checking out. If so, then you can use such tools or apps as your 'real' speedometer.