Cars with ambitious speedometers

[addz86]

The Golf R's speedo goes up to 200mph

[Bodo]

h0b0 said:

Bodo said:

h0b0 said:

RDMcG said:

My 991RS has a 350 km/h speedo.....217 MPH. Not even close. Maybe 190 in effect conditions.

They have allowed for the vast over reading of Porsche speedos. Mine reads over 10% over actual speed and that's even with the optional 21" wheels.

My 987 VDO speedometer over reads around 5%@100km/h - compared with phone GPS.

A variance of 1% accuracy (for wheel speed, taken from a Hall sensor) in the serial production of speedometers with pointers driven by stepper motors should be feasible.
Porsche specifies the accuracy of their speedos in accordance to homologation requirements:

UN ECE R39 said:

5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1) and the true speed (V2).
0 ? (V1 - V2) ? 0.1 V2 + 4 km/h

Basically that means when you're driving 100km/h, your speedo has to show a value between 104 and 114km/h.
At 190mph, this would read between 192.5 and 211.5 (theoretically - as the highest calibration speed is 75mph).

https://www.unece.org/fileadmin/DAM/trans/main/wp2...

Edited by Bodo on Saturday 14th January 14:54

The 15+ cars I've had (in the US) all read within 1mph of the GPS I was using. This is the first car I've had with Gps built in and the speedo is way out. (But, as designed by Porsche) even my wife's Tiguan is spot on.

Sounds about right for the US - which has different requirements for speedo indication; ie. it is allowed to indicate a lower speed than driven, and the specification has the freedom to come closer to the actual speed:

article said:

...
So we sought out the rule book to find out just how much accuracy is mandated. In the U.S., manufacturers voluntarily follow the standard set by the Society of Automotive Engineers, J1226, which is pretty lax. To begin with, manufacturers are afforded the latitude to aim for within plus-or-minus two percent of absolute accuracy or to introduce bias to read high on a sliding scale of from minus-one to plus-three percent at low speeds to zero to plus-four percent above 55 mph. And those percentages are not of actual speed but rather a percentage of the total speed range indicated on the dial. So the four-percent allowable range on an 85-mph speedometer is 3.4 mph, and the acceptable range on a 150-mph speedometer is 6.0 mph.
[...]
The European regulation, ECE-R 39, is more concise, stating essentially that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70). Never low. Not even if somebody swaps a big set of 285/35R-18s for stock 255/45R-16s.

There's your explanation of high-reading European speedometers, with the highest readings on Porsches and BMWs that are most likely to lure owners inclined to fool with tire sizes.
...

http://www.caranddriver.com/features/speedometer-scandal

The mentioned difference with tyre diameters might be ok for the US, but cars homologated for Europe are -on paper- limited in their tyre type and sizes.

Australia, on the other hand, has the highest requirements on indicated speed; so if you're comparing an Australian market car with the GPS, you will get different results again.

In short: you can have a J1226 or Australian or ECE speedo in the US; but in the EU, you will in any case have an ECE speed indication, and in Australia, you will have Australian accuracy.

Edited by Bodo on Saturday 14th January 23:36

[RDMcG]

My 991RS is Canadian Spec (basically identical to US) and the speedo accuracy is not bad..about 1-2% optimistic compared to GPS. As I mentioned the 350km speedo is amusing and would require the auxiliary PRL accessory to get there ( Porsche Rocket Launcher).....

[Bodo]

RDMcG, the 350km/h end is probably to reduce instrument variants, in case someone orders the Schnell-Package with their 911. Didn't happen yet, since the intern forgot to put it on the option lists.

[FunkyNige]

Was going to start a thread on this until I found this old one as my new car's speedometer goes up to 180mph. What is this streamlined powerful car? Land Rover Discovery Sport! Book says the top speed is 130 so an extra 50mph is a tad on the ambitious side...
What makes it even worse is that it's an electronic dash so it's just a software thing that makes it go up this high, not like the old days when they had the same physical dial on all cars in a range.

[Eyersey1234]

My old Fiesta had 130mph on the speedo even though its top speed according to Ford was 96mph.

[ch37]

dme123 said:

That really, really pissed me off on the nasty repmobile Audis I used to have to borrow from work. They confine the actual bit of the speedo you use to 1/3rd of the dial area, make it harder to see accurately what speed you are doing at a glance. If they will insist on giving a car that will struggle to do 130mph a speedo that goes up to 180mph they could at last weight it as you say.

Must be another part of the amazing VAG ergonomics that I just don't get, like armrests that foul the handbrake. It would be poor for a Chinese car and yet people just accept it.

Well over half of the speedo in my Citigo is in the 'legal' range (60mph is right at the top) and it's pretty huge, so they appear to have fixed this in some cars.

[nipsips]

My 2020 1.5 diesel 308 SW 100bhp has a very optimistic 160mph Speedo. Not that I use it I use the dial just the digital display.



Also appears to step up like the Rev counter. Don’t look at that either, the rattles tell you when it’s time to change gear 😂

[66mpg]

My work van, a Transit Courier has a speedo marked up to 130mph. Pity it’s limited to 62mph. I’ve never seen it go past 65mph, exactly half of it is superfluous.

[SuperPav]

I think Porsche speedos are the worst in terms of being optimistic + having a short sweep.

In the example above, the sweep from 0-80mph is less than that of the fuel gauge. The speedometer becomes almost useless at that sort of resolution.

Thank god for digital read-outs!!

[Shnozz]

My Vantage. 220mph meaning if the digital readout isn’t on speed or a fault code has rendered it out of action then you struggle to see speeds of 30/40mph come city centres.

[anonymous-user]

Some Corvettes sold as official stock in Europe have a 300 mph speedo - Oooh matron!

The catch is the increments on the dial are so small the instrument is virtually useless and you rely on the digital heads-up display instead.

[DaveH23]

My 13 year old Mazda has 180 on the clock. Don't think I've ever taken it over 100.

Can't say I'm one for top speed thrills.

[MrGTI6]

My 306 has a claimed top speed of 135mph and the speedo goes up to 140mph.

I used to have an R-reg Transit where the speedo went up to 150mph! The needle couldn't get much further than halfway round the dial.

The speedo on the current Astra goes up to 180mph, even in the 1.0-litre triple.

[alfa-alex]

Alfa 156 GTA - 200mph on the clock!

More chance of swimming the channel with a gas oven strapped to my back!

[s m]

Lotus Carlton could have done with a more ambitious one
Only went to 180

[CanAm]

The most ambitious speedo I've ever seen was on a 322cc Berkeley sports car which read up to 145mph. It could just about manage 60 mph.

I think a lot of modern cars read up to 140 so that 70 is at top centre.

[Mr Tidy]

It's usually because manufacturers just make one speedo for the whole range that will cope with top of the range models.

My 1990 Sierra Sapphire 2.0GLSi had a 150 mph speedo, because the Cosworth of that era got close to that - before it got chipped!

[BigR]

My 1957 190SL has 140mph on the clock. Who knows what anyone has ever taken it up to, but approaching 70mph feels ambitious enough these days frankly.

[Triumph Man]

The least optimistic speedo is that in my 530i - speedo reads to 155mph, and the car’s apparent top speed is 155mph. No idea how much it overreads by though - I had 145mph indicated once but no idea what the actual speed was!