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YOUR RESEARCHSpeedometer Error
Leading reported evidence
Test on
Performed · outcome unconfirmed
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0
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1
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
It passed smog easily, but I noticed that the cars speedometer was reading 4 to 5 MPH high compared to the smog machine it was being tested on.
Leading evidence: 'Test on' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Test equipment is accurate' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
So I performed a 64.3 mile test using a GPS that I use for sailing against the cars speedometer and odometer.
Use sailing against the cars speedometer and odometer
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Performed · outcome unconfirmed · Original poster
So I performed a 64.3 mile test using a GPS that I use for sailing against the cars speedometer and odometer.
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Suggestion · Original poster
And I assume the state is going to be pretty fussy about making sure the test equipment is accurate.
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Suggestion
The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds.
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Rennlist: 1 discussions
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Generation: 20261026T190023Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
This topic has been partially covered in previous posts but I thought I would share my findings.
When I bought my 56K miles 996 a couple of weeks ago, I had to have it smogged to transfer title. It passed smog easily, but I noticed that the cars speedometer was reading 4 to 5 MPH high compared to the smog machine it was being tested on. I asked the tech about it and he said that of course his machine was right on and the cars speedo had to be off. That's not hard to believe since the rollers that spin the tires could be easily designed and constructed to consistently duplicate a correct speed. And I assume the state is going to be pretty fussy about making sure the test equipment is accurate.
Wow, I thought maybe I have 50k mile car not a 56k mile car! So I performed a 64.3 mile test using a GPS that I use for sailing against the cars speedometer and odometer. All the driving was done on the freeway with the top down for optimum sattelite reception.
I found that the cars speedometer was indeed 4 to 5 mph high compared to my GPS. The variation was not a % variance, it was a consistent 4 to 5 mph overstating.
I also found that the cars odometer was dead on compared to the GPS track log. Thus, the car odometer was not reading high, and in fact I feel comfortable that the miles on the odometer are reasonably accurate. The analog speedo is too hard to tell since the width of the needle is just about 4 to 5 mph anyway, and I didn't like staring at the analog guage while zipping down the freeway.
All that said, some earlier poster made comments that all speedos regardless of manufacturer read high. I also tested the speedo of my 2005 Toyota 4Runner, and the Toyota was dead on at all speeds. I prefer knowing what speed I am actually going without having to do the extra calculations
Speedo is off by design. Your odometer is correct though. Same on BMWs.
A bit of background:
http://en.wikipedia.org/wiki/Speedometer
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European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers [5] [6][7] are similar to the UNECE regulation in that they specify that:
1.The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
2. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.
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Since it is not possible to be dead on because of tire wear and other variations in measurement, a European manufacturer/vendor needs to build-in a cushion of a few mph just in case to make sure they always abide by #1.
FM
This is a source reference. Confirm exact model applicability in the original material.
