RPM vs indicated speed vs REAL speed vs odometer accuracy

[Jabba]

On my standard...

3000 rpm = 60 mph INDICATED = 56 mph ACTUAL
1 ACTUAL mile = 1.07 INDICATED miles.

On my IS...

3000 rpm = 65 mph INDICATED = 61.3 mph ACTUAL
1 ACTUAL mile = .96 INDICATED miles

Tires are the same size, though different brands.  Both front and rear.  205/60/16 NMS tires on both.  Metzeler on the Std and a Dunlop E3 on the IS.

It doesn't make sense to me that the SPEED on the IS indicates HIGHER than actual, but the mileage is lower.  Don't the speedo and odo both read off the front wheel?  and off the same gear?  Shouldn't they be represenative of one another? 

Do I have a taller (aftermarket) OD gear in my IS?

Inquiring minds want to know...

 

Jabba

 

[NITRO]

I don't know why the difference exists between the actual and indicated, but I can tell you that your IS results are the same as I've seen on mine.

Your standard results are slightly different, but very close to my old Standard.

[Black Dog]

Pretty close to mine (Standard)...  Above 50 mph, there seems to be about a 5mph difference between indicated and actual (indicated 60 = real 56, indicated 75 = real 70)...  Also, in 5th gear, 2500 RPM = 55 mph indicated.  New E3's on the front and rear.

Black Dog

[Ricky-D]

There are two different systems used in the different Valkyrie's.

The Interstate uses an electrical sensing device right there at the wheel and transmits it to the brainbox in the fairing speedometer where the computation is performed, stored(odometer) and displayed.

The Standard is fully mechanical from the drive at the wheel to the gearing in the speedometer, where the speed is displayed and stored.

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[Mildew]

When I got my speeding ticket  the officer got me at 74. I just came out of a turn on a 2 lane with the speedometer between 70-75. I was running a 205/55/16

[Jabba]

There are two different systems used in the different Valkyrie's.

The Interstate uses an electrical sensing device right there at the wheel and transmits it to the brainbox in the fairing speedometer where the computation is performed, stored(odometer) and displayed.

But on the IS... if the speedo says I'm going FASTER than I actually am... shouldn't the Odo record MORE miles than I actually went?  

That is NOT the case.  It's mixed... and THAT doesn't make sense to me.

Also... do ya'll THINK I have an aftermarket gear?  I was under the impression that the transmissions and final drives were identical between std and IS models.  Why are mine different?

Jabba

[roboto65]

My IS does the same thing on the speed have never checked the distance though but if I am doing 70 my GPS says 65ish !!!

[Jabba]

I think they ALL do that to some extent.  The speedo's on ALL our valks say we're doing faster than we really are.

My questions are specifically about the difference between the two bikes... and the rpm's vs the speed.  And WHY does the IS say I'm not going as far as I am, when the speedo says I'm going faster than I am.  It shorts my brain!

Jabba

[roboto65]

Maybe because Speed is not realitive to Distance just because you go faster which is natural on a Valk does not mean you go any further you just get there faster !!!!  

[TearlessTom]

How are you measuring your milage down to 1/100th?  I think your #s may be too precise to be accurate if that makes any sense.

Are you sure you are not doing your math backwards.  Is your gps reading 0.96 miles and your odo 1 mile or vice --versa?

Explain to us your methodology.?

(I'm taking a statistics class if you are wondering about the questions)

[Cattman]

Jabba, mines the same as yours. The mileage is less due to our larger cargo being hauled.

[Jabba]

How are you measuring your milage down to 1/100th?  I think your #s may be too precise to be accurate if that makes any sense.

Are you sure you are not doing your math backwards.  Is your gps reading 0.96 miles and your odo 1 mile or vice --versa?

Explain to us your methodology.?

(I'm taking a statistics class if you are wondering about the questions)

I did it over a 600+ mile trip.  I compared the Odo mileage vs the GPS miles traveled on the trip computer part of the GPS.  And yes... I think I got it right.  GPS said 670 miles while the Odo said 643.  I'll double check it at shorter distances... but that wil lose accuracy.  I am on my standard today too, but I'll check it again on my way home after work.

Jabba

[Jabba]

Jabba, mines the same as yours. The mileage is less due to our larger cargo being hauled.

We're probably aboput even Catt.  I am bigger than you... but you got a lot more crap bolted onto yours...   

Love ya brother.

You riding anymore?  Going to the Whiskey Run?  Inzane?

Been thinking about stopping by your house and surprising you sometime.  You should join us at the Johnson County Libertarian meet-up sometime soon.  I'll but you dinner.  Last Thursday of EVERY month.

Jabba

[Warlock]

On my standard...

3000 rpm = 60 mph INDICATED = 56 mph ACTUAL
1 ACTUAL mile = 1.07 INDICATED miles.

On my IS...

3000 rpm = 65 mph INDICATED = 61.3 mph ACTUAL
1 ACTUAL mile = .96 INDICATED miles

Tires are the same size, though different brands.  Both front and rear.  205/60/16 NMS tires on both.  Metzeler on the Std and a Dunlop E3 on the IS.

It doesn't make sense to me that the SPEED on the IS indicates HIGHER than actual, but the mileage is lower.  Don't the speedo and odo both read off the front wheel?  and off the same gear?  Shouldn't they be represenative of one another? 

Do I have a taller (aftermarket) OD gear in my IS?

Inquiring minds want to know...

 

Jabba

 

There is a difference, but I have found in the past that the E-3 are a little taller than the other tires. With the smaller tire on your standard it will make it indicate faster than it is going.JAT
David

[Willow]

  You should join us at the Johnson County Libertarian meet-up sometime soon. 

You and I both live in Johnson County?  The parallels are almost frightening.    

On my Standard my speedometer reads high, but the odometer records 9.7 miles per ten.  I think that's fairly normal.

I use the mile markers to check.  Long distances for GPS's and odometers may tend to differ as the odometer is measing wheel turns and the GPS is spot checking locations at x(?) second intervals.  My GPS usually shows itself to be accurate withing ten to fourteen feet and thus may miss some movement such as lane changing and just general wobbling within the lane.  Those subtle movements are measured by the rotation of the tires method.

I'd compare on a shorter interval unless you can get 400 miles of dead straight road.    

[TearlessTom]

How are you measuring your milage down to 1/100th?  I think your #s may be too precise to be accurate if that makes any sense.

Are you sure you are not doing your math backwards.  Is your gps reading 0.96 miles and your odo 1 mile or vice --versa?

Explain to us your methodology.?

(I'm taking a statistics class if you are wondering about the questions)

I did it over a 600+ mile trip.  I compared the Odo mileage vs the GPS miles traveled on the trip computer part of the GPS.  And yes... I think I got it right.  GPS said 670 miles while the Odo said 643.  I'll double check it at shorter distances... but that wil lose accuracy.  I am on my standard today too, but I'll check it again on my way home after work.

Jabba

600 miles is certainly enough to get an accurate reading. Just wanted to make sure that you were not basing it on just a few miles and the mile post signs on the side of the road.

I think I’ve got it figured out but now I gotta figure out how to explain it.

I am left handed so my thought process is a bit off from norm.

Okay here goes:

I took your numbers and based them on 100 rather than 60 to make it easier to work with percentages.

The short version is this:

For every 100 miles (or mph)your bike is seeing itself travel  93.34 miles or (93.34mph)

In order for it to actually travel the full 100 miles it must travel an additional 6.66 miles. So you indicated distance will be more for a fast speedometer.

Now your indicated distance of  1.07 miles to make 1.0 miles gives us : 1.00/1.07= 0.934

0.934x100=93.4 just happens to equal your distance of what the bike thinks it traveled (93.4 miles instead of 100 miles)

So your readings on your Standard prove to be correct as you have them

Now I thought I had this figured out until I re-read the IS part…Damn!



Okay now;  for every 65 miles your bike see itself going you have only traveled 61.3 miles

So 61.3 miles / 65 miles = 0.943 miles which is only 0.017 off from your reading of 0.96. Indicated for an actual 1 mile

I think this is right but you might want to ask those smarter than me to recheck my logic.

Tom

[TearlessTom]

PS: My Tourer reads 68 mph at 3000 and it is dead on in speed and mileage with all three of my GPS.

I run the stock size E3's

Now that weird!!

[MP]

My 97 is 6% reading fast on the speedo, but is VERY close on the odometer.  The reason is, federal regulations require that the speed read "at least" as fast" as you are going, so they err on the high side.  But, they have the odometer set to be about right.  Just depends on the gearing between them.

MP

[roboto65]

Also we have to take into consideration the GPS's accuracy. And it reads like this...

GPS receivers are accurate to within 15 meters on average.  Thats 45 ft well a little less but hey 

Now  WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average. Thats 15 ft Ok OK I know less  but average that over 600 miles and how far off are you!!

[Jabba]

  You should join us at the Johnson County Libertarian meet-up sometime soon. 

You and I both live in Johnson County?  The parallels are almost frightening.    

We're both married to Lori's too.

Blue skunks.
Green IS's.
Johnson county.
Lori's.
Weird facial hair.

All I know is... I better not grow up to be you.  Like some sort of Back to the Future sort of thing...

Jabba

[N8171S]

I just returned from a trip where the GPS  total was 4403 and the odometer reading was 4381.5  The gps showed 68 MPH at 3000 RPM with a Bridgestone potenza 205/60/16  With my carbs syncd at 3000 this year I got 37.9 mpg.  Last hear with them syncd at idle I only got 32.2 on an almost identical trip.

[TearlessTom]

Also we have to take into consideration the GPS's accuracy. And it reads like this...

GPS receivers are accurate to within 15 meters on average.  Thats 45 ft well a little less but hey 

Now  WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average. Thats 15 ft Ok OK I know less  but average that over 600 miles and how far off are you!!

Actually it is a bit more than 45 feet, 48.75 to be exact and 3 meter is 9.75 feet. 
Anyway your point is well taken and I thought of that as I was out riding this afternoon.

However I think the errors would pretty  much cancel themselves out for the most part. An error to the left would be cancelled out by one to the right, one to the front would be cancelled by one to the rear.
I think where the difference would be made is in the curves. If it is tracking to the outside of the curve vs the inside it will show more distance.  or less distance. 

A difference of less than 2 tenths of a mile over a 100 mile stretch is pretty accurate if you ask me. Unless your NASA and shooting for the moon. That could be disastrous.

[valkyriemc]

On other bikes, the diff can be considerable. Most folks would rather see, say 70 and actually be going 66 mph or so. But over a period of time you can rack up more miles on your bike than actually traveled, read accerated depreciation. So they now make a device called a "speedo healer". As long as you are interested in a general range of mph they work well, but rarely are bikes linear through the entire speedo range.

http://www.healtech-electronics.com/

[Jabba]

Can ANYONE explain the Interstate reading FASTER than it's actually going, but recording LESS miles?

That just doesn't make sense to me.

Damn... we have a calibrated speedo check course just south of me... I am goona have to make a run down there I guess.

Jabba

[Cliff]

Can ANYONE explain the Interstate reading FASTER than it's actually going, but recording LESS miles?

That just doesn't make sense to me.

Damn... we have a calibrated speedo check course just south of me... I am goona have to make a run down there I guess.

Jabba

Perhaps the wheel sensor output is split in the circuitry,, one path feeds circuit for ODO and the other path for speedo,, that would explain how they could be different??>>>>> I just looked over the I/S wiring diagram and it does appear to be a split with one line going to ODO and other to speed sensor, with that in mind (2 seperate circuits) it is possible to have the "disagreement between the speed indicated vs miles traveled.

[vanagon40]

Okay Jabba, suppose we accept Cliff’s theory that speed is calculated independently of distance.  And lets further suppose that the two calculators are net necessarily calibrated identically.  Then everything can make sense.

Lets say for example, that by design, when the front wheel with the OEM front tire on your Interstate was spinning at 765 rpm, the bike was traveling at 60 mph.  But lets also suppose that some Honda Engineer said, “Hey, I have a speedometer that reads 66 mph with a 765 rpm pulse,” and the designer says, “Close enough, lets use it.”  And they do.

Now, you being an engineer, when asked to design the odometer, would say, “OK, if the speedometer reads 66 mph at 765 rpm, I need an odometer that will read 1.1 mile after 765 rotations.”  But the designer says, “Dude, just because the speedometer is fast, does not mean I have to design the odometer fast.  Lets make the odometer read exactly 1 mile after 765 rotations.”  And they do.

I have no idea if this is anywhere close to reality, I’m just making it up as I go along.  (Maybe an electrical connection somewhere has a little bit of resistance due to corrosion.  It is not a mechanical speedometer.)  But the concept is that the speedometer does not have to be calibrated to MATCH the odometer.

Now, check out the next step.

Previous Owner buys the bike we designed above and wears out the front tire.  He puts on a tire that is 4% larger in diameter.  Now, when the bike is traveling at 61.3 mph, the speedometer reads 65 mph (actual mph * 1.1 design error * .96 tire correction) and the odometer racks up only .96 miles for every mile ridden.

With regard to the RPMs vs. actual speed, remember that the diameter on two tires (even though both are 205/60/16) are not identical (design, tread wear, pressure).  Add any error in calibration of the RPM gauge (and any possible error in reading the gauge).  A difference of a little less than 10% does not seem too out of line.

[Jabba]

Okay Jabba, suppose we accept Cliff’s theory that speed is calculated independently of distance.  And lets further suppose that the two calculators are net necessarily calibrated identically.  Then everything can make sense.

Lets say for example, that by design, when the front wheel with the OEM front tire on your Interstate was spinning at 765 rpm, the bike was traveling at 60 mph.  But lets also suppose that some Honda Engineer said, “Hey, I have a speedometer that reads 66 mph with a 765 rpm pulse,” and the designer says, “Close enough, lets use it.”  And they do.

Now, you being an engineer, when asked to design the odometer, would say, “OK, if the speedometer reads 66 mph at 765 rpm, I need an odometer that will read 1.1 mile after 765 rotations.”  But the designer says, “Dude, just because the speedometer is fast, does not mean I have to design the odometer fast.  Lets make the odometer read exactly 1 mile after 765 rotations.”  And they do.

I have no idea if this is anywhere close to reality, I’m just making it up as I go along.  (Maybe an electrical connection somewhere has a little bit of resistance due to corrosion.  It is not a mechanical speedometer.)  But the concept is that the speedometer does not have to be calibrated to MATCH the odometer.

Now, check out the next step.

Previous Owner buys the bike we designed above and wears out the front tire.  He puts on a tire that is 4% larger in diameter.  Now, when the bike is traveling at 61.3 mph, the speedometer reads 65 mph (actual mph * 1.1 design error * .96 tire correction) and the odometer racks up only .96 miles for every mile ridden.

With regard to the RPMs vs. actual speed, remember that the diameter on two tires (even though both are 205/60/16) are not identical (design, tread wear, pressure).  Add any error in calibration of the RPM gauge (and any possible error in reading the gauge).  A difference of a little less than 10% does not seem too out of line.

Leave it to a Lawyer to "clear" things up.

Yeah, I got it... but as an engineer... I'll say this... Not MANY of us design types are bery happy about saying... "Yeah, close enough!".

That's one of those things that makes my skin crawl!

Jabba

[vanagon40]

Hey, I don't know that Honda said "close enough."  Again, I just made that up to demonstrate that the odometer does not have to be calibrated to match the speedometer.

And my first degree was a BSEE from Purdue.

[Jabba]

Hey, I don't know that Honda said "close enough."  Again, I just made that up to demonstrate that the odometer does not have to be calibrated to match the speedometer.

And my first degree was a BSEE from Purdue.

Not saying ANYTHING Van.  You made a good hypothetical arguement, which I appreciate very much, however, as is often the case with legal arguements, we're in EXACTLY the same place we started.

Again... nothing REALLY personal.  I know that's how you guys operate.  I have a couple very good friends that are lawyers, and they are the same way.  We'll argue about something we all agree on for hours... and get no closer to solving the problem.  Again... it's hard to get into an internet post, that I really do appreciate the thought process that you guys have.  But it's also easy to see why people make jokes about lawyers.  (As well as about engineers) My only defense is that I'm not REALLY and engineer.  I just pretend to be while I am at work.

Is it POSSIBLE that I got thru all that without offending you?

 

Jabba

[vanagon40]

I think I'm like you.  You have to say a lot more about me, and likely something about my wife, mother, or daughter before I am offended.

[Jabba]

I think I'm like you.  You have to say a lot more about me, and likely something about my wife, mother, or daughter before I am offended.

I'll bet your wife, daughter and mother are all WONDERFUL people... and the fact that they tolerate a dirty ass, motorcycle riding Engineer-Lawyer PROVES it!

Jabba

[Rocketman]

Perhaps the wheel sensor output is split in the circuitry,, one path feeds circuit for ODO and the other path for speedo,, that would explain how they could be different??>>>>> I just looked over the I/S wiring diagram and it does appear to be a split with one line going to ODO and other to speed sensor, with that in mind (2 seperate circuits) it is possible to have the "disagreement between the speed indicated vs miles traveled.

Concur.
Even on the mechanical ones, there are enough odo-specific parts to make some error between the two.

[Hoser]

It ain't no big deal,  I hardly ever ride the speed limit,  and I suspect most other Valk drivers  don't either.    hoser

[Jabba]

My issues ain't eith the speedo.  It's with the PUZZLE of it being slower and not traveling as far.  It creates a paradox in my brain.  There have been enough theories tossed in here I guess so that my brain ain't melting anymore.  Although... I am still trying to get the issue of a different gear in the IS worked out in my brain.  I have been having GPS malfunctions lately.

I'll figger it out eventually.

Jabba

[Rio Wil]

I am guessing these 2 circuits work something like this.

The odometer is a simple digital counter, lets say the input is from a tire that turns 800 revolutions a mile.  Then when the digital circuit receives 80 pulses it increments the .1 digit,  160 pulses, it increment the count to .2. When it counts 800 pulses it increments  the units position to '1'.  This counter doesn't care how fast or slow it receives pulses, it just counts to 800 and increments the unit, tens, one hundred positions, etc.

The speedometer is a digital to analog circuit, it takes the same pulses in and then outputs a analog signal that is proportional to how "fast" the incoming pulses are, the faster they come the higher the output voltage.  The output voltage/current is sent to a electromechanical device with a magnet arrangement that allows a pointer to deflect at a rate that is in relation to the amplitude of the voltage/current.  The outer circumference is annotated with mph numbers and hot dog we got a speedometer.  The mechanical portion of the pointing device can be made to be quite linear over a broad range and produce a very accurate speed measuring device.

So, the two circuits take the same digital input pulses but the operate very differently as to how they use them.  Thus the accuracy or inaccuracy of the two circuits have no relationship to each other.

[Jabba]

Best tech explanation yet.

Jabba

[BigMacMT]

Not sure the mechanics of the odometer but I learned on the Goldwing forum that Japanese bikes are usually off 5-10%. The reason is that manufacturers would be heavily fined by our Gov. if the speedometers were off the other way so they made sure that wouldn't happen by reading 5-10% faster than actual speed. Made sense to me & both my previous bike, an 83 Goldwing & my present bike 99 Valk I/S is off by about 5% or so.

[Kymbo]

Now I have a headache 

[Kymbo]

Mind you wouldnt the speed and milage change as the diameter of the tyre decreases with wear and therefore everytime you ride you will get a different reading as each ride removes more rubber

[Ricky-D]

Rio Wil hits the proverbial nail "right on the head"

The mechanical speedometers are the same only the "signal" is a turn of the speedometer cable.

The two operations, speed and distance, although related are computed differently in each instance.

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