Speedo Calibration

[bill3422]

When calibrating the speedometer, once in calibration mode and traveling the 2 mile run, is there a speed that needs to be maintained?

[michael everson]

no
Mike

[phileas_fogg]

To amplify on what Mike said, the speedometer is counting pulses from the speedo sensor in the transmission. You don't have to maintain any set speed, and you can speed up or slow down as you desire / the road dictates.

Cheers,


John

P.S. Bill, you're quite the lurker. Only 104 posts in 6 1/2 years? Wow!

[bill3422]

104? Wow, that many? Thank you for the information.

[srobinsonx2]

Like others have said, you can go any speed you want.

The first time I calibrated my speedometer, I went "about" 2 miles. That was not good enough. I checked my speed with a GPS unit and it was off by about 10 mph at highway speeds. I recalibrated and went exactly 2 miles. Now I am pretty accurate. Hope that helps. Good luck.

[chopthebass]

I haven't done mine yet, but I would like to understand how it can calibrate knowing the number of pulses.

[edwardb]

I haven't done mine yet, but I would like to understand how it can calibrate knowing the number of pulses.

Because you go a prescribed distance. Number of pulses / distance = speed calibration value it stores.

[AC Bill]

Depends on the speedo..
The Classic Instruments speedo calibration was done by maintaining a set speed. I used a hand held GPS to give me a speed read out, then adjusted the black box until the speedo read the same. We then tested it at several speeds, and checked the odometer against hwy mile markers, and it was dead on.

[Papa]

Are people still using the VSS from the trans even with the GPS gauges? If so, what is the reasoning; more accurate?

[edwardb]

Depends on the speedo..
The Classic Instruments speedo calibration was done by maintaining a set speed. I used a hand held GPS to give me a speed read out, then adjusted the black box until the speedo read the same. We then tested it at several speeds, and checked the odometer against hwy mile markers, and it was dead on.

I assumed the question was about the Speedhut gauges, since they seem to be the most common. Autometers also calibrate in a similar manner. But you're right. Classic Instrument gauges do require you to drive a fixed speed. My Mk3 build had those. That was a while ago, but looking at their current instructions appears it's still the same.

Are people still using the VSS from the trans even with the GPS gauges? If so, what is the reasoning; more accurate?

The VSS can't be used with GPS gauges. No wires to hook one up plus no internal mechanism to use the signal. The gauge is one or the other. I have the GPS gauge in my #8674 Roadster. Based on what I can tell, it's dead on accurate.

[AC Bill]

I assumed the question was about the Speedhut gauges, since they seem to be the most common.

That is true. In spite of all the issues people have had with the Speedhut, they still seem the most popular. I presume that's because, that's what comes in the Complete Kit.
You'd think FFR would offer the Classic Instruments, and perhaps the Smith gauges, as optional choices, but perhaps there's not enough profit in it for them.

[Al_C]

OK, maybe I'm hijacking the thread (for which I apologize), but it is related... check out the photo. The connector for the speedometer at the transmission has two white wires. The wires from the gauge connector (classic) is one white, one black. Or in the RF bundle, one white, one gray. I have to believe that it does matter which way you connect it. But which way? Thank you for not getting annoyed at this slight diversion.

[AC Bill]

My roadster wasn't wired with the RF harness, but I was led to understand it makes no difference, as long as one of the leads from the VSS is grounded. My Classic speedo works fine.

[Papa]

Since I have the GPS speedo, what should I do with the harness and opening in the driver's side trans tunnel wall? I suspect I could eliminate the harness, but not sure if it's better to keep it and just wrap it up.



I'll just silicone a patch over the hole unless it is needed for something else.



Thanks,
Dave

[weendoggy]

I'd just tape the end and leave the connector in tact. You never know..... Also, just cut a small piece of aluminum (if the kit didn't come with the plate) and place it over the hole with silicone and rivets. I'd put the rivets in from the transmission side because you have insulation/carpet that will not show the rivet plug. Later on you know why when you're under there doing work and catch your hand on the rivets if you put them in from the cockpit side.

[Papa]

I'd just tape the end and leave the connector in tact. You never know..... Also, just cut a small piece of aluminum (if the kit didn't come with the plate) and place it over the hole with silicone and rivets. I'd put the rivets in from the transmission side because you have insulation/carpet that will not show the rivet plug. Later on you know why when you're under there doing work and catch your hand on the rivets if you put them in from the cockpit side.

Perfect!

[michael everson]

Your kit came with a patch for that location. Looks like an oval with one end cut so it had a straight area.
Mike

[Papa]

Your kit came with a patch for that location. Looks like an oval with one end cut so it had a straight area.
Mike

Thank you. I'll track that down.