718 Speedo Error
#19
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#21
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Here's a fun interactive calculator. Fill in the gear ratios and tire diameter to see what your true speed should be for any gear/rpm.
https://www.blocklayer.com/rpm-gear
https://www.blocklayer.com/rpm-gear
Last edited by Z06jerry; 03-15-2023 at 07:56 AM.
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reacp911 (03-15-2023)
#23
Saw this thread the other day and decided to pay attention to speedo accuracy on my car.
My Uniden R3 has a gps speed display and it is dead nuts the same as my dash indicated speed. My car is an 18CGTS on stock sized tires. If my speedo is fast then the GPS in the uniden is miscalibrated as well.
My Uniden R3 has a gps speed display and it is dead nuts the same as my dash indicated speed. My car is an 18CGTS on stock sized tires. If my speedo is fast then the GPS in the uniden is miscalibrated as well.
#24
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@reacp911 My BGTS speedo also reads high. There does appear to be a calibration menu in PIWIS 3. I haven't adjusted mine yet due to winter conditions but plan to do so in the near future. Our Alltrack is also very accurate but our Audi Allroad not so much.
** Edit ; The last three lines translate to velocity calibration characteristics.
** Edit ; The last three lines translate to velocity calibration characteristics.
In addition to differing gear ratios , manual vs PDK and variations in tire OD this may help to explain why some have accurate speedos while others do not. I haven't tried to adjust any settings yet as my GTS is still in storage but will look into this in the future.
velocity characteristics for GT4
Speedo characteristics, RDW , UK, USA
UK x4-x8 do not equal y4-y8
UK x4-x8 do not equal y4-y8
USA x = y
USA x = y
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reacp911 (03-23-2023)
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x = speed received by the instrument cluster
y = speed the cluster displays
I'm guessing we Canadians get the RDW calibration, not the USA calibration, but I can't confirm since my car is up on the hoist atm
y = speed the cluster displays
I'm guessing we Canadians get the RDW calibration, not the USA calibration, but I can't confirm since my car is up on the hoist atm
Last edited by Z06jerry; 03-23-2023 at 04:34 PM.
#27
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^^^ its similar to the coolant temperature calibration. With GT4s and Spyders x = y but GTS 4 (and probably all non GT's temps from x = 80.3c to x = 110.3c are displayed as y = 90c. This why our coolant temp always reads 90c while the actual temp is up to 15c warner (in Normal mode)
Last edited by Z06jerry; 03-23-2023 at 04:45 PM.
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reacp911 (03-23-2023)
#29
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Oh, been meaning to look into the proper software for Porsche diagnostics. I have ISTA+ and VAGCOM running on a windows 7 virtual machine on mac air. Both work fine. I could not get VAGCOM working on Windows 11 on my new MacBook although others have reported it works on M1 chip Macs...>I have to figure that out.
Anyway, do you know if PIWIS supports VM's on macs???
Mike
Anyway, do you know if PIWIS supports VM's on macs???
Mike
#30
I've been meaning to test this by changing the wheel size (Clubsport custom sizing per wheel) and comparing speedo to GPS. I should be able to do this on the weekend