Speedometer

Yep. And it's a bit squirrely that in my '04 and '11, if I set the cruise control to 70mph, the speedo would almost always match that setting. On the '14 PiP, the car gets up to 72mph on the display pretty routinely. It's irritating but not significant.

 

ditto. been there, done that.

 

What does +2-3 mean?

 

off by 2 or 3 mph.

 

Yes it is 2 mph for me. However on 2011 prius changed tires and almost matched up.

 

Judging by the fact that everyone seems to be reporting the same speedometer error, it looks like Toyota has either planned this, or they have made the same mistake consistently. I'm seeing 2-3% more speed indicated than actual speed, therefore it's possible that this would translate to what appears to be 2-3% more miles per gallon of gasoline. Not a bad thing for advertising purposes.

 

Its planned, but not for the purposes you may think:

Speedometer - Wikipedia, the free encyclopedia (takes you directly to the "international agreements" section)

 

I still think it's for purposes I described. An accurate speedometer should be the easiest thing to achieve in a car like the Prius.

 

But if every auto manufacturer abides by the "agreement", then that would make MPG relative amongst all vehicles.. which would defeat the purpose of doing it for MPG reasons. And while we're at it, why not just go for the maximum allowable. In the given example, at 80kmh, you can be off by as much as 15%. That would be quite a healthy bump in MPG.

And as I mentioned in a previous thread where this topic came up, you also have tires issues to contend with. I agree that an accurate speedo should be do-able with today's technology. But how would you account for all the differences in tire rolling diameter amongst different manufacturers, not to mention regular tire wear.

 

or maybe it keeps the car from under reporting speed in case of wear or tyre change, and getting a ticket for going 33 in a 30 when your speedo says 30.

 

I'm going to go out on a limb and say that the speedometer could be self-calibrated from the nav-unit, if they wanted it to be accurate.

 

As mentioned in this and other threads about speedometer bias, in addition to the international agreement, no automaker is going to subject themselves to a lawsuit for under-reporting actual speed. I just realize that my speedometer reads 2-3 mph high, no big deal.

 

It is so easy for the Toyota to report a true (let's just say within %1 of Garmin gps) that they did. It is available via the dongle under the steering wheel with ScanGuage II or torque setup.

I like that you reported +2 to 3 percent higher MPH rather than +2 to 3 MPH higher Greg, as I see the difference between the speedometer and the CAN BUS dongle based reading increase as speed increases.

 

That probably won't happen until Nav units become universal, rather than optional or trim-specific.

 

I have a Scangauge, my 2007 Prius is matching MPH with Scangauge MPH. My 2014 PiP is 3 miles OFF (3 Miles Higher than the Scangauge).

- The 2014 PiP 70 MPH Scangauge 67 MPH
- The 2014 PiP 55 MPH Scangauge 52 MPH

I saw the ICE is kicked in when PiP speed o meter at 61 0r 62, Scangauge RPM is change from 0 to xxxx around 58 MPH.

 

How much is the PiP off at 20MPH?

 

Mine at 30 mph is about right on. At 65 mph it is about 2 mph slow. Just my best Est.

 

Except the ODOmeter is the only relevant device for MPG calculations. Instant speed indicated on the speedometer is not relevant whatsoever to fuel consumption.

Although it seems counterintutive, the fact the SPEEDometer is off by +2-3% does not mean the ODOmeter is off by that same proportion. In fact, if it were, there would be lots of class action lawsuits for fraudulent early termination of warranty coverage.

 

Yup. Both Honda and Subaru were hit with such suits while I owned those cars, and both settled for warranty extensions.
BTW, neither of those cars of mine had significant odometer errors.