How accurate is your speedo?

Using a SatNav & speedometer app on my phone I recently discovered my EP3's speedo might be out by quite a bit. At and indicated 70mph on the speedo, my SatNav was showing 66mph, & likewise 50mph the app was showing 45mph . I was surprised, that's nearly out 10%. Anyone else notice this with their Type R?

This inaccuracy is well known.
On the early 8G models it was indeed 10%, reduced to about 6% on MY09 models. The 9G Civs are about 3%.

If you want to correct it, and are OK with DIY, you can install a 'Speedo Healer'. Designed for bikes but works anyway.

Oerlikon said:

Using a SatNav & speedometer app on my phone I recently discovered my EP3's speedo might be out by quite a bit. At and indicated 70mph on the speedo, my SatNav was showing 66mph, & likewise 50mph the app was showing 45mph . I was surprised, that's nearly out 10%. Anyone else notice this with their Type R?

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Thats pretty normal tbh. I've never found a speedo to under read, they always say im going faster than i actually am. I usually go by the 10% rule

In my current Astra i do an indicated 60mph during the 50mph average speed check commute.

Mine seems most accurate somewhere between 30-40mph, below that it under reads slightly, above that it over reads (I have to be doing a little under 80 on the dial to read 70 on GPS). However, remember that GPS isn't a bed of roses either, each reading is out by a likely 10m, so the speed reading is generally a best-guess that only works out on long averages and could be out significantly at lower speeds in cities (due to stop-start and lower visible satellites due to buildings in the way)

Even worse on the Stagea, that's been converted to mph and badly over reads once you get over 40-50 mph. I've worked out speeds according to rpm so I know I'm okay.

Krzys said:

Even worse on the Stagea, that's been converted to mph and badly over reads once you get over 40-50 mph. I've worked out speeds according to rpm so I know I'm okay.

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I ended up replacing the old km/h to mph adapter in my Prelude, it helped quite a bit, more modern digital solutions may well be a lot better than older ones or something. Not too expensive to do either.

mike.h said:

I ended up replacing the old km/h to mph adapter in my Prelude, it helped quite a bit, more modern digital solutions may well be a lot better than older ones or something. Not too expensive to do either.

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Should think it's a modern unit as the car only came into the UK in December last year but I may look into a different unit if it'll make a difference.