Speedometer/odometer calibration?

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ChickenPinz
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Speedometer/odometer calibration?

Post by ChickenPinz »

Has anyone embarked on recalibrating their speedometer/odometer? My speedo is about 9% fast and odo is about 13% fast.

Of course I could take it to a shop, but I'm wondering about DIY options.
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rmel
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Re: Speedometer/odometer calibration?

Post by rmel »

I believe classic Porches e.g. 911 use VSO mechanical Speedo's
and is the same basic design as the Pinz -- though "clocked" a wee
bit higher to 150 Km/hr.

You might find this link interesting. Not an easy re-cal job.

http://forums.pelicanparts.com/porsche- ... ation.html

cheers,
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
ChickenPinz
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Re: Speedometer/odometer calibration?

Post by ChickenPinz »

Thanks. Given that the odometer is also pretty fast, seems like a gearing question, and unless the drive gears in the transmission can be changed, it'd mean that gears in the odometer would have to change.

Anyone happen to know if the speedometer section of the speedometer/odometer is direct-drive from the cable input, or if there are places where gearing could be changed internally to recall the speedo+odo? I've not seen a Pinz speedo teardown.

And to preempt those who will suggest an electronic replacement, I'm trying to keep the Pinz as close to stock as practical.
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RPinAZ
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Re: Speedometer/odometer calibration?

Post by RPinAZ »

If I remember correctly, the odometer/trip meter are gear driven from the input cable. The speedometer is indirectly driven. The input cable turns a magnet that fits inside a cup (but the magnet and cup don't actually touch each other - there's an air gap). The other side of the cup has a shaft on it with the speedo pointer attached. There's a hairspring attached to the shaft to return the pointer to zero when the magnet quits turning. When the magnet turns, it exerts a force on the cup due to eddy currents induced and the cup tries to keep up with the magnet and that turns the pointer more and more as the magnet turns faster.

-RP
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Mr Zero
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Re: Speedometer/odometer calibration?

Post by Mr Zero »

Rather than re-gearing the speedometer itself, have you considered a gear box ratio adapter...?

https://speedometercablesusa.com/gear_box_adapters.html
Jason @battlebornpinzgauer
[1975 Pinzgauer 710K 2.7L EFI, 1972 700AP Haflinger Pathfinder]
ChickenPinz
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Re: Speedometer/odometer calibration?

Post by ChickenPinz »

Mr Zero wrote: Mon Aug 29, 2022 9:20 am Rather than re-gearing the speedometer itself, have you considered a gear box ratio adapter...?

https://speedometercablesusa.com/gear_box_adapters.html
YES! That's exactly what I was hoping for. Now....do you know if they'll have any idea what Pinzgauer is, or is it the same as something more common?

If anyone knows the right parts to fit the Pinz, that'd save some effort and perhaps trial-and-error. I've reviewed their catalog and it might be doable by measurements.
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Mr Zero
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Re: Speedometer/odometer calibration?

Post by Mr Zero »

ChickenPinz wrote: Tue Aug 30, 2022 10:41 am YES! That's exactly what I was hoping for. Now....do you know if they'll have any idea what Pinzgauer is, or is it the same as something more common?
I don't know. I'm familiar with the concept in general, but have never installed or used one. It's an inline component that fits at one end or the other of the speedometer cable (Example below of a ratio adapter for Dodge and GM trucks.) I imagine that if you can establish that the Pinz uses a common standard for the speedometer cable and what that is, then the only other variable to identify the proper adapter would be the % difference needed to correct the guage reading, which it sounds like you've already determined. An adjustable adapter would be nice, but I don't know if that option exists.

Image
Jason @battlebornpinzgauer
[1975 Pinzgauer 710K 2.7L EFI, 1972 700AP Haflinger Pathfinder]
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