Wow, I was wondering why my hand-calculated FE was consistently 3% lower than the OBD. I just put in the same "adjusted 1.5% miles" calculation into my spreadsheet, and now my hand-FE is within 1% of the OBD. Still doesn't explain why I'm still 5% lower than the OBD on my last two tanks after over-inflating my tires, but that's another discussion!

 

I think there is a typo here. 69.0 - 61.9 is a big difference. You said the odometer read 0.9 miles less than the actual distance. It seems quite odd that the odometer would read low, yet the speedometer reads high (70mph vs 67mph via your GPS)

 

Nash: There is a typo error, it should 61.0, (odo),and 61.9,(GPS).
Thanks for pointing out this error.

 

The speedometer reading is intentionally biased but the odometer is not.

Ken@Japan

 

The speedometer shows 70mph, but the SGII shows 67mph, so the ECU actually knows the actual speed of 67 and displaces the speed at 70.

I think the odometer will be accurate as the ECU knows the actual speed or distance traveled.

 

Mine kicks in around 44-45 mph

 

I use a GPS worn on my wrist with a built-in barometer (Garmin forerunner 205) when I run that helps minimize the error of a GPS reading when multiple elevation changes are involved. I have a freind who also runs with a GPS, but it is a marine GPS (no barometer since it thinks you are always at sea level) and his reading differ by about ~.08 per mile on relatively flat areas, but the change is more drastic in relation to extreme changes in terrain. I am wondering which car devices have this added feature. I doubt my garmin street-pilot has this. Just wanting to put my 2 cents in FWIW.

http://wiki.motionbased.com/mb/GPS_Unit_Elevation

http://ohioline.osu.edu/aex-fact/0560.html

 

Sorry to bring up this old thread again, but I am still upset over this "intentional" speedometer error. It is by far, the thing I most dislike about my TCH.

I recently rented a new Toyota Yaris. I know, it was cheap, and I only needed basic transportation from airport to hotel for two people, beside, it gave me an opportunity to see what other cars are like that get over 30mpg in the city. Anyway, it wasn't bad for what I needed it for, but I couldn't get used to the speedo in the center of the dash.

Back on subject...the speedo read the exact same speed as my Garmin. Soooo... If a very LOW-tech car also built by Toyota, and also sold internationally, has an accurate speedo, why, oh why, doesn't our high-tech TCH have an accurate speedo? WHY?????!!!

OK, finished Ranting

 

You can corrert your speedo empirically. Just inflate your tires to various, different, pressures until you find the one that makes the speedo/odo correct. Of you could wait until the tire tread wears down to the "correct" circumference....

 

Do you know what model year the Yaris is?

Anyway, let me explain what's going on in Japan.
Japanese government decided to follow the UN ECE regulation No.39 in 2001, and they set the transition period until 2006. It became mandatory to follow the regulation for vehicles sold in Japan after January 1st 2007.
The speedometer value on the 2001-2003 Prius was set very accurate, then it has a few % higher offset on the 2004 and later Prius.

Does anyone have any information how the US government sets the speedometer regulation?

Ken@Japan