Tesla speedometer calibration

[ajdelange]

Afraid you are: ὁδός, a path, a way, a road (in Athens, a lane). An odometer measures/records distance traversed. You are confusing it with an "hour meter". In the BEV (MX) I drive the odometer, as is the case in every car, BEV or ICE I have ever owned, is tied to the wheels. It shows the total mile driven and thus gives the prospective buyer a fairly accurate idea as to how much the car has been used. By contrast every airplane I flew had a "Hobbs Meter" which was just a timer activated by engine oil pressure. Its purpose was to record engine hours between inspections, major maintenance events and in the case of rented planes how much to charge.

In the olden days one could detach an odometer cable and run it backwards or reset it in other ways. More recently laws have been enacted to make that difficult and illegal.

As you list occupation "TBD", use "boy" in your user name and don't know what an odometer is I have to ask: "Are you old enough to drive?" If not you must be the youngest guy on this site which seems to be mostly populated by old retired farts (like me).

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[Crissa]

The odometer on my motorcycle - and most motorcycles - is rotations are the motor. Which means that to display miles, it need to know the sprocket ratio and tire size.

-Crissa

 

[TI4Dan]

The ABS system in most vehicles have speed sensor in each wheel, The ABS computer has dual processors which are dedicated to to wheel control and on some vehicles it also controls the engine ECM, cars that have traction control or stability control can have the driver input taken over by the ECM. For instants a car is driven in road conditions with patchy ice on road way and one wheel spins faster than the rest of the wheels, ABS may send a signal to the EMS to retard the engine in order to regain wheel traction. In some conditions the brakes may be applied but it has to do with road speed observed by the ABS. Some vehicles have the ability to turn off the ABS system, this is very useful when driving up a steep hill in snow or muddy and other low traction situations where basically you are going to spin the tires to get through. Most vehicles get the speed reading from a speed sensor located on a output axle or drive line. Odometers are a requirement for car makers and it is a federal crime to tamper with a odometer or disconnect it from vehicle and operated it, just in case if anyone wanted to know.

 

[FutureBoy]

Hmmm...... I may be vastly mistaken here but I was thinking that odometer readings were particularly used to measure the usage history of an engine.

In the BEV (MX) I drive the odometer, as is the case in every car, BEV or ICE I have ever owned, is tied to the wheels. It shows the total mile driven and thus gives the prospective buyer a fairly accurate idea as to how much the car has been used.

So you are confirming my assertion that the measurement is a way of determining the "usage" (me) / "how much the car has been used" (you). I skipped mentioning where the measurement was taken from but we seem to be at the same endpoint.

My real point is that "how much a car has been used" is most useful as a proxy measure of reducing risk for very complex items like an engine and largely invisible damage like internal wear. For the rest of the vehicle, distance doesn't have the same weight as say maintenance records, accident history, driving on salted roads, etc.

So back to my real question, if an engine is not involved and there are no really complicated internals that are dependent on distance, is an odometer reading really of any practical use? For an EV the real risk would be around the batteries instead of the motors. So better measures to track might be things like:

• # of battery charges
• average max charge percentage
• average charge dissipation percentage

I'm not saying that an odometer reading is useless, but it certainly would have much less value to me for an EV than for an ICE vehicle.

As you list occupation "TBD", use "boy" in your user name and don't know what an odometer is I have to ask: "Are you old enough to drive?" If not you must be the youngest guy on this site which seems to be mostly populated by old retired farts (like me)..

Yes, I am old enough to drive. I haven't been looking around at profiles to see what everyone describes themselves as but I doubt I'm the youngest around here.

 

[ajdelange]

So you are confirming my assertion that the measurement is a way of determining the "usage" (me) / "how much the car has been used" (you).

Clearly an odometer's intended use is to record the overall use of the vehicle. It's analogue in the aviation industry would be "airframe hours". Your opinion as to whether it is a useful metric or not is immaterial. It has been in use since way back when and will continue to be used for this purpose into the future. It is required by law.

The thing you need to be clear on that it is divorced from engine hours as a new engine could have been fitted when the car had quite a few miles on it. In lots of places (Australia comes to mind) you don't buy a car without a detailed logbook (similar to what is maintained for aircraft in the US). All repairs are listed there.

Yes, I am old enough to drive.

OK. Next question (tell me if I am getting too nosy) is do you have a driver's license? The reason for asking this is I just can't fathom that anyone that operates a motor vehicle wouldn't know what that little thing on the bottom of the speedometer with the 6 numbers showing is.

 

[Crissa]

OK. Next question (tell me if I am getting too nosy) is do you have a driver's license? The reason for asking this is I just can't fathom that anyone that operates a motor vehicle wouldn't know what that little thing on the bottom of the speedometer with the 6 numbers showing is.

Did you read his first post on this thread?

Hmmm...... I may be vastly mistaken here but I was thinking that odometer readings were particularly used to measure the usage history of an engine. For instance, I have a family friend who exports low mileage engines out of Japan and they have to have odometer readings for each engine.

So what do odometer readings help for in an EV? Especially in cases where some EV's have separate motors that may or may not even be engaged all the time. Like in a 2 motor scenario for a vehicle that only uses the front motor if it needs to engage AWD.

I get that an odometer reading can be somewhat telling of a vehicle as a whole but if the measurement is really just a reading of how much use the engine has on it, what is the use for a vehicle that does not have an engine?

Maybe the odometer laws need to get updated...

Yeah, we need some pretty specific health of battery pack statistics. Odometer readings will match motor rotations, so that's not so bad, but what we really need is a way to check the health and capacity of a battery. Its cycles are a decent measure, but as the Leaf showed, not all cycles are made equal.

-Crissa

 

[FutureBoy]

Clearly an odometer's intended use is to record the overall use of the vehicle. It's analogue in the aviation industry would be "airframe hours". Your opinion as to whether it is a useful metric or not is immaterial. It has been in use since way back when and will continue to be used for this purpose into the future. It is required by law.

The thing you need to be clear on that it is divorced from engine hours as a new engine could have been fitted when the car had quite a few miles on it. In lots of places (Australia comes to mind) you don't buy a car without a detailed logbook (similar to what is maintained for aircraft in the US). All repairs are listed there.

I get that it has been. And I get that the law requires it. And I get that it's going to be around for a while yet. Just not sure it is so useful or that it can be relied on in the same way. Laws often get outdated. Years later we look back and find laws that sound ridiculous. Seems like odometer laws might become one of those. Eventually... In a time far far away.

OK. Next question (tell me if I am getting too nosy) is do you have a driver's license? The reason for asking this is I just can't fathom that anyone that operates a motor vehicle wouldn't know what that little thing on the bottom of the speedometer with the 6 numbers showing is.

Yes, I have a driver's license. And have had driver licenses internationally where the requirements were MUCH more stringent.

I'm going to leave be your disabled fathoming as a sign of misattributed speculation.