" It is my fifth "Iron Butt" 1,000 mile ride this year." Damn, that's hard core. I tip my hat to you for sure...

 

So in other words you are saying that you are relying on what the ECU estimates for fuel usage which is likely based on fuel pressure and injector size / PW..

 

Like most ECU estimates, probably based more on remaining fuel and average speed. Just a guess.

 

Miles to empty. Yes.
Gas mileage. No.

I doubt fuel tank levels are calibrated.

 

If you have miles to empty you already have gas mileage, it's how you got miles to empty. It's math. And I meant Distance, not speed. Half awake my bad.

Miles ran (odometer) / gas used (Full fuel reading - current fuel level reading) = mileage

Average Mileage * Fuel remaining = Miles to empty

 

OK how well is the bold part calibrated? What happens when you fill the tank all the way up or 2 inches from the filler ring? When does the ECU know? What does the ECU know?

It's easier to learn (and more accurate) that some point on the fuel level to some other part on the fuel level means mileage between the 2 points. The software learns how far it is between the 2 points based on adding up injector PWs between those 2 points.

Fwiw some here have had issues with mileage to empty. The reason is that the ECU lost calibration between those 2 points.

Give it a shot if you have a integrated GPS that shows mileage. (My bike don't) Compare mileage that the GPS gets versus mileage that fuel measured at the pump versus mileage on a trip meter Do it 3 or 4 time to make sure the first time, you weren't lucky. More than one person needs to do it also. Especially those that are getting 52 MPG.

In other words check the calibration..

 

I'm going to type a bunch of crap because this interests me.

I know what you're saying but No, it's not calculated based on spray.
I wish it was, as it would be more accurate like you've said, but instead it's typically a slew of measurements using the formula above which is then averaged in real time over and over.

Overfilling can affect the outcome and is why typically, you can get that scenario where the thing says you have 50 miles to empty, you run 2 miles and suddenly it's telling you are empty.
It's because the meter hit bottom before the ECM said it would, and that is because the ECM did/could not properly average due to the extra fuel.
In this case you can run down through the "extra gas" and make your first gallon look like 70 miles per gallon where the next gallon and all those following are only getting say 37.
If averaged it appears to the ECM that you're getting 42.5 miles per gallon for a full tank when in reality you're getting 37.

So anyway, when people post average mileage from one single tank directly from the bike (ECM) I usually don't put too much stock in that.
If it was a long trip (say 19 hours and multiple tanks) the law of averages takes over and it becomes pretty accurate.
If you've averaged your mileage manually using odo and gas filled, then Yes, very accurate, one tank or many.
If your manual measurement and the ECM measurement match... you're doing great.

Anyway, interesting.

 

How to you get miles per gallon from miles to empty?

 

The only accurate way to determine fuel mileage is to hold the bike straight upright, not on the side stand, fill the tank until fuel is lapping at the filler hole.
Then pick a 50+ mile route that will provide constant speeds and loads. Run tha route each way.
Then return to the gas station and repeat the fill up procedure.
Now you have real numbers to calculate actual mpg.
If folks change rear belt/chain drive ratio and/or change tire outside diameters without proper recalculation of speed, all bets are off due to errors built into the calculations.
IMO, any other method is suspect to errors.
Bob

 

My M8 Road King in the 1st 1000 miles hasn't strayed to far off 40. It always amazes me when these MPG posts come up how different riders mileage vary's. I could understand 10% but lots of times we're talking 25% or more.