How does the Speedo calculate range?
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Joined: Nov 2012
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From: Philly
How does the Speedo calculate range?
As I toggle through my Slim speedo, there is an indicator for miles left on the tank, or range.
It works pretty well, changing with every fill up, but I wouldn't test it close in.
Since the computer doesn't have avg or instantaneous MPG in its readout, I have to assume that this works by a simple calculation of an MPG constant multiplied by the gas gauge readout.
Does anyone know the constant used by the MoCo and if that constant changes when you add pipes and an AC?
It works pretty well, changing with every fill up, but I wouldn't test it close in.
Since the computer doesn't have avg or instantaneous MPG in its readout, I have to assume that this works by a simple calculation of an MPG constant multiplied by the gas gauge readout.
Does anyone know the constant used by the MoCo and if that constant changes when you add pipes and an AC?
Seasoned HDF Member
Joined: Feb 2006
Posts: 5,351
Likes: 648
From: Vegas, baby!
As I toggle through my Slim speedo, there is an indicator for miles left on the tank, or range.
It works pretty well, changing with every fill up, but I wouldn't test it close in.
Since the computer doesn't have avg or instantaneous MPG in its readout, I have to assume that this works by a simple calculation of an MPG constant multiplied by the gas gauge readout.
Does anyone know the constant used by the MoCo and if that constant changes when you add pipes and an AC?
It works pretty well, changing with every fill up, but I wouldn't test it close in.
Since the computer doesn't have avg or instantaneous MPG in its readout, I have to assume that this works by a simple calculation of an MPG constant multiplied by the gas gauge readout.
Does anyone know the constant used by the MoCo and if that constant changes when you add pipes and an AC?
I have always assumed that it uses mpg, since last reset, times gas left in the tank to get the miles left. I would guess that your Slim doesn't use a constant, but instead calculates the mpg.
Just because there is no display of your mpg doesn't mean the computer doesn't know what your mpg is. I'm not familiar with a Slim, does it have a gas gauge or a low fuel light? If so then the computer knows how much fuel is left in your tank, and can calculate your mpg.
It might know how much fuel is left even if it doesn't tell you (the rider). Using a constant wouldn't offer much accuracy.
Ron
Last edited by rjg883c; Jul 13, 2013 at 10:51 AM.
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From: Philly
Just because there is no display of your mpg doesn't mean the computer doesn't know what your mpg is. I'm not familiar with a Slim, does it have a gas gauge or a low fuel light? If so then the computer knows how much fuel is left in your tank, and can calculate your mpg.
Ron
With EFI is there a fuel mass meter that knows how much fuel is passing through the jets?
Road Master
Joined: Aug 2012
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From: Where I lay my head is home.
Fill it up, see what it says... divide by fuel capacity. Go riding. Fill it up, see what it says... divide by fuel capacity. Go riding. Fill it up, see what it says... divide by fuel capacity. If those three numbers are basically the same... you have your answer. If they're not... you also have your answer.
My truck seems to calculate by the MPG of the last 50-100 miles. If I use it for nothing other than short errands and towing equipment around the job for a few weeks... when I get on the highway... the range will go up steadily.
My truck seems to calculate by the MPG of the last 50-100 miles. If I use it for nothing other than short errands and towing equipment around the job for a few weeks... when I get on the highway... the range will go up steadily.
Tourer
Joined: Sep 2012
Posts: 344
Likes: 8
From: wisconsin
ah yes. don't rely on that. it's not accurate. i've been using my 2nd trip meter. i filled when i ran it low once with 30 miles left and it only took 3.5 gals. here is my comment on this the other day.
https://www.hdforums.com/forum/softa...-accuracy.html
https://www.hdforums.com/forum/softa...-accuracy.html
Outstanding HDF Member
Joined: Apr 2010
Posts: 2,477
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From: Western MD
as far as i know in cager pcm/ecm the fuel mileage calculation is done by an algorithm in the computer software program. i don't believe that HD would be any different. the manufacture knows the estimated miles per gal, of the vehicle based on eng rpm, load (by tps, map sensor and or air flow meter), air/fuel ratio(O2 sensor), eng temp, speed and gear. it takes all this info and calculates remaining miles per tank or mpg whichever you all looking at. in cagers, it also uses this info to turn the "Change Oil" light on among other maintenance reminders.
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Joined: Feb 2006
Posts: 5,351
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From: Vegas, baby!
There is a simple way to check if the 'range' displayed is valid. Fill up the scooter and check the 'range'.
Ride a known set of miles 10,20,50, etc. and see if the range lowers a corresponding amount. That would be a way to know whether it could be trusted.
Even if it isn't rocket science, relying on an estimated mpg would seem not to be an accurate method of calculation. Too many variables to consider.
Ride a known set of miles 10,20,50, etc. and see if the range lowers a corresponding amount. That would be a way to know whether it could be trusted.
Even if it isn't rocket science, relying on an estimated mpg would seem not to be an accurate method of calculation. Too many variables to consider.
Last edited by rjg883c; Jul 13, 2013 at 09:14 PM.
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Road Master
Joined: Dec 2010
Posts: 1,248
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From: Jacksonville, NC
I find the range estimator to work pretty good for me, in fact I don't bother to use the gas gauge at all and only really bother with the trip meter if it's a long ride. I ride to work everyday and the estimator works pretty good to remind me when it's time to top off the tank. Is it dead on, no, but it's good enough. I've been thinking about getting rid of the gauge and going to the RSD gauge and gas cap. The RSD gauge only has a low fuel light. I probably would have made the switch by now but I can't find out if the estimator will still work or not.
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