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post #1 of 13 (permalink) Old 12-19-03, 08:03 PM Thread Starter
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Speedometer accuracy...

Ok, quick question, how could I find out how accurate my speedometer is?

Living in the speed camera city (aka Melbourne), I want to make sure my speedo is as accurate as possible, in fact I'd prefer for it to read slightly over (so for example read 60km/h when I'm actually doing 59km/h) - I want to at least be able to stay at or under the speed limit when going past those revenue raising machines, oops, I mean road safety devices...

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post #2 of 13 (permalink) Old 12-20-03, 11:57 AM
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Re: Speedometer accuracy...

Have you tried the speedo check on the side of freeways and H'wys? Over 5 kms, signs posted at the start, and then every km. Check against your odometer.

Also, run your car behind a car who's speedo you trust, and go through various speed zones, noting what speed your car is telling you.

Some Dyno shops can also tell you on the dyno run (or they have on a couple of runs I have had done).

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post #3 of 13 (permalink) Old 12-20-03, 01:36 PM
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Re: Speedometer accuracy...

Try using a hand held GPS they are pretty good

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post #4 of 13 (permalink) Old 12-24-03, 06:46 AM
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Re: Speedometer accuracy...

Here's how I do mine:

1. get to desired speed on speedo and set cruise control. Try to do thiis on a flat section of road.
2. Cycle your trip computer until you get to the 'average speed' reading and hit reset.
3. After a second you will get a reading which is a pretty good indication of your current speed.

I know that when my speedo is reading 100 I'm doing about 97, when it reads 110 I'm doing about 105. So for me to be doing 110 (say on the way to the Gold Coast) I set my criuse control to 115. Now all those cars don't creep away from, or up to, me!

i know that my friends EBII is rthe same, apparently ford and few other makers set their speedo's this way for a reson. Sounds dumb I know but hey, go figure. Apparently Australia is one of two or three countries in the world that still allows this practice.
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post #5 of 13 (permalink) Old 12-24-03, 03:12 PM
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Re: Speedometer accuracy...

Chase a couple mates, not all of them will have speedos that are out that much....

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post #6 of 13 (permalink) Old 12-24-03, 03:33 PM
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Re: Speedometer accuracy...

There are places that accurately test and calibrate speedos, I sometimes work on fire trucks and once a year it goes for a test. I would expect that the police cars also need to be calibrated. Or they give a printout of the speedo reading and actual speed difference
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post #7 of 13 (permalink) Old 12-24-03, 04:31 PM
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Re: Speedometer accuracy...

Speak to a cab company they tend to have their speedos checked, they should be able to tell you where to get it done

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post #8 of 13 (permalink) Old 12-26-03, 05:14 AM
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Re: Speedometer accuracy...

If you're doing it on an EF/L you can use the Dash Diagnostic mode to find out exactly how fact you're going:

* Turn Smartlock Off, put your keys in the ignition and hold down the odo button. Count to about 12 (keep holding it in).

*Whilst still holding the button in, turn the keys to the 'on' position, but dont start the car. Let go of the button, then push it quickly 3 times, holding it in on the third time. Hold it in until the seatbelt light (in the middle of your teacho) goes out, once it goes out let the button go.

*If you've done it right, the odo should black out for about 5-8 seconds, then start flashing 'FORD' at you. You can now turn the car on.

*Once you're driving push the odo button until you see a '3' in the top left hand corner. At this screen, the bottom row of numbers is the vehicle speed, and it is exact. If your speedo is set right it'll be 3kms out (this is normal factory setting), so 100 on your speedo will equal 97 in your odo doing this test. The top line is engine RPM.

*If you keep cycling through (by pressing the odo button to move to the next screen) you can find battery voltage, fuel tank level etc etc - lots of other things that I cant be bothered writing out. If anyone wants to know the rest I'll post it up later.

*To exit dash diagnostic mode, hold your odo button in for about 3-5 seconds. It should go back to normal after that.

WARNING: If you're driving with Dash Diagnostic mode operating, it is more than likely your engine will stop for half a second or so after around 10 mins of operating in this mode. Your gauges will go back to zero, then they should return to a reading of your current speed/RPM, and the dash will automatically exit diagnostic mode.

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post #9 of 13 (permalink) Old 12-26-03, 05:20 AM
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Re: Speedometer accuracy...

Put it on a dyno and get the guy to note what speed your speedo reads for each applicabble speed limit. eg when my speedo says 85 im going 80.

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post #10 of 13 (permalink) Old 12-26-03, 06:44 PM
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Re: Speedometer accuracy...

Go to a professional place to get it measured.
Anything that the car is telling you (cruise or diags panel) is subject to the same inaccuracies the speedo itself is - tyres, the speedo gears etc etc.

Personally, I haven't got a great deal of faith in the roadside "calibration" postings, but it might be better than nothing. Oh, and don't trust any of the govt "speed notification" signs that tell you how fast you are travelling on a road - they are notorious for being wrong . . .
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