Prius Mark 3 Top Speed

[chi tang]

I was on the autobahn and drove my Prius to 122MPH. It could probably go that little bit more but I only wanted to stretch its legs and didn't really wanna go all out.

So I came home and went to the Toyota website and the book says the cars top speed is 109MPH.

Can anyone else comment on this?

[CPN]

Did you consider the fact that the car's speedo will be at least 10% reading high which actually means you were doing 122-12.2=109.8 which is close enough to the quoted 109 to be valid?

[FROSTYBALLS]

UK regulations stipulate that above 70mph speedometers should not read more than 110% of the actual speed. So 110% of 109mph is 119.9mph, or 120.

[johalareewi]

I thought the gen3 was speed limited to 112mph not 109mph?

My gen3 reports approx 7% above actual speed.

112 * 1.07 = 119.84.

[PeteB]

Gen 1 Prius limited to 99 mph (106 on speedo)

Gen 2 limited to 106 (112)

Gen 3 112 (121)

Those that reported on Gen 1s on the autobahn said it had plenty of power right up to the limit then the engine management prevented further acceleration.

[chi tang]

no i didn't know it shows 10% more, which now makes sense.

[PeteB]

It's a European thing - the car's internal network uses the true speed, as does the SatNav for speed limit warnings, it just fudges it for the speedo display.

If you buy a Prius in places like Japan or USA, I understand the speedo shows the true speed.

[YarisHybrid2016]

That's stupid! What's the point of that?

[CPN]

Thank the gnomes in Brussels for that! This is an example of the psychological games they "play" on the citizens that they think are a bunch of irresponsible toe rags incapable of driving sensibly and keeping to the proper speed limits. So, they mandate that the cars over read in a silly attempt to get everyone to slow down in real terms... Well, that's my theory anyway lol... ;)

[FROSTYBALLS]

The UK has slightly different speedometer regulations to the EU and the regulations date back to 1986 (although amended from time to time sincd then). The difference is that for speeds between 25mph and 70mph, the indicated speed must not exceed 110% plus 6.25mph - so for a vehicle travelling at a true 40mph, the indicated speed should not exceed 40.25mph. A speedometer should never under-read.

Ok modern speedometers are a lot more accurate (certainly compared to GPS the speedo on my Auris doesn't over-read by much) but don't forget that there are older vehicles on the road whose speedometers may not be as accurate, and the permitted variance also allows for things like changes in tyres and wheels which may affect speedometer readings.

[johalareewi]

That's stupid! What's the point of that?

What Frosty said plus, if you are making a car and you have to ensure the speedo is never below the true speed and never more than 10% (+ a bit) above the true speed, what speed are you going to show the driver?

[PeteB]

Mind you, even old style (rotating cable driving springs & magnets in the head unit) speedos could be surprisingly accurate.

In the 1970s/80s there was a road near where I lived where the local traffic police had put 2 marker posts exactly a quarter of a mile apart. They used them to prove their calibrated speedos were accurate.

I often took cars past with a stopwatch and found Fords were very inaccurate, Fiats ludicrously so (a 132 2 litre was 15% optimistic!). Surprisingly, an Austin Allegro was spot on at every speed I tested it, and a Morris Marina almost as good, being 1 mph over at 60 indicated.

they think are a bunch of irresponsible toe rags incapable of driving sensibly and keeping to the proper speed limits

They may have a point. I can count on one finger the number of people I see in an average day making any serious attempt to drive legally.

[CPN]

Sadly, I can't disagree with you... :(

[YarisHybrid2016]

That's stupid! What's the point of that?

What Frosty said plus, if you are making a car and you have to ensure the speedo is never below the true speed and never more than 10% (+ a bit) above the true speed, what speed are you going to show the driver?

Modern technology means there is no reason not to have very accurate speedos. Even an accuracy of -0/+1 MPH is not unreasonable, if they're worried about under-reading.

[FROSTYBALLS]

'Modern technology means there is no reason not to have very accurate speedos. Even an accuracy of -0/+1 MPH is not unreasonable, if they're worried about under-reading.'

.... but the current speedometers which may over-read by up to 10% meet the appropriate legislation, so there is actually no reason for manufacturers to improve accuracy of speedometers.

[johalareewi]

'Modern technology means there is no reason not to have very accurate speedos. Even an accuracy of -0/+1 MPH is not unreasonable, if they're worried about under-reading.'

.... but the current speedometers which may over-read by up to 10% meet the appropriate legislation, so there is actually no reason for manufacturers to improve accuracy of speedometers.

And to avoid being sued for under or over reporting speedometers, the best bet is to over report by 5%.

[cootuk]

People have got used to doing 35 in a 30 zone etc, knowing that the true spped is close to 30 - make it bang on and they start getting close to being caught out.