After doing a 4-day 354 km = 220 mile test that used up a full tank of fuel in my 2023 RG3, I think I have to regretfully accept that the HD Trip Info screen (“TIS”) is a mix of truth and serious fiction. I also learned how easy it is to accidentally cause it to display completely untrue and mangled information.

I had long suspected that the TIS was accurate in reporting the distance covered during a trip. It was also believable in its average speed calculated for the trip.And it displays a running trip-so-far average fuel MPG or Liters/100km that appeared accurate compared to the displayed distance traveled and the fuel consumption the TIS claimed.

But I knew there has to be something wrong with the trip-so-far fuel consumption displayed, because it seemed notably too low, and so consequently made the average fuel consumption number look way too good.

I had reported all the above in a prior posting thread on fuel mileage.

I set up this test to make it relatively “easy” for the TIS to obtain and display accurate numbers. I set up a “trip” to a destination I would never reach, so the trip would never end. I ran routes on all 4 days of testing at the same, modest, cruise-controlled speed: 82 kph = 51 MPH = 2114 rpm. The only deviations from this speed were for getting in and out of town (2km in and 2 km out each time), for stop signs when changing county road type highways, and for u-turns midway through each day’s segment of the total trip (to ensure that any helpful or adverse wind effects would be equalized in their effects. The test continued each day until the fuel tank was declared buy both the TIS and the fuel gauge to be close to “empty”.

I also manually “topped up” the gasoline in the fuel tank to the tips of the toothed ring in the tank’s filler tube, repeatedly before the test, until the fuel level stopped falling. This was an effort to combat the inconsistency of the “fullness” of the tank, as the hD 6 gallon tank seems to trap a bubble of air, that can prevent as much as a full liter of fuel from completing the fill. The only way to defeat this air bubble is to iteratively wiggle the handlebar, or dive the front fork, while holding the front brake, to break it up and allow fuel to be added after each wiggle or dive. This way, I could actually approach closely the actual full capacity of the tank. This was done immediately before starting the test (which consumed

I figured if the TIS could not be accurate under these very tight controls, it could never be accurate in a typical real world mix of riding speeds, varying numbers of stops and idling, and differing fuel fill-up techniques..

The results are summarized in the following sequence of photos, which I will elaborate on for each:






The above photo shows the TIS right after the engine was shut off, after the test, at the gas station. Note that the trip in total covered 354 km = 220 miles. Since this almost drained the tank, I can conclude that my true “fuel range”, from a tank filled with particular care, is really only 354 km = 220 miles under fairly ideal conditions (51 mph, modest winds, very few stops).

Next, notice that even with the strict controls on speed and minimizing traffic stops (stop signs, traffic lights) and minimized non-highway distances traveled, the “average” speed is still only 69 kph when the cruise controlled speed was 81 kph, so roughly 15% below sustained cruise control speed. This is why short distance tests cannot provide accurate enought data.

Notice next that the TIS says that only 15.94 liters of fuel were consumed for the entire 354 km. And, that the ITS therefor calculated the average fuel consumption, “correctly”, as 4.5 Liter / 100 km, which is 52.3 miles / US gallon. Do YOU believe that? I did not.

Notice next, in the speedometer portion of the instruments, below the TIS, that the fuel “Range” remaining is claimed to be only 28 km. If you believe the optimistic 4.5 L/100km average fuel consumption, then I should have been able to go 28 more km using up 28/100 x 4.5 liters of fuel = 1.26 liters of fuel. So, basically the TIS is saying I have at least about 1.26 liters of gas still available.

But the TIS says I consumed only 15.94 liters so far, so 15.94 + 1.26 = 17.2 liters would be the ENTIRE fuel capacity of the fuel tank! But HD says the gas tnak hold 6 gallons = 22.7 liters. So, what happened to the missing 22.7 -17.2 = 5.5 liters = 1.45 gallons? is that really “unavailable” for some reason? Of, does hD hide that 5.5 liters = 1.45 gallons as a hidden “reserve” so that riders won’t get pissed when they run out of gas because they did not look at their fuel gauge?

Speaking of the fuel gauge, here’s what it looked like before refilling at the gas station:






Note that it is deep within the red zone just above “Empty”. That would seem to support the TIS’s claim that there IS only a remaining range of 28 km = 17.4 miles.

Note also that the trike gave me a “low fuel” alert at exactly 325 km on the TIS. That was 354 minus 325 = 29 km before the gas station. And remember the TIS said I had 28 km of rnage left at the gas station before the fill-up. That means it snapped the low fuel alert on when it thought I had only 29 + 28 = 57 km of range left in the tank. But, since the TIS claims average fuel consumption is 4.5 liters / 100km, that also means that 57 km of range is 57/100 x 4.5 = 2.6 liters left in the tank when the low fuel alert snapped on. For you U.S. guys, that’s only 0.68 of a gallon.

Now, let’s look at what the TIS showed just 1.4 km after the fill-up at the gas station:






Note that since the TIS does not display decimals on total trip distance traveled, it incremented the 354 to 356, instead of to 355.4 km.

Note that it updated the fuel used to reflect the 1.4 km ride to home.

Note that it continues to display average fuel consumption of 4.5 L / 100km.

But note that it has now updated the “range” from 28 km to 454 km (assuming that I will continue to ride at the same speed). it did this because it now senses I have a re-filled tank. But a 22.7 liter full tank, consuming fuel at 4.5 L/100km would use up the entire tank of 22.7 liters in 22.7 / 4.5 x 100 = 504 km ! NOT 454 km. So, the TIS is evidently assuming a smaller usable total tank capacity than the 22.7liters HD claims. The difference of 50km, at the same consumption rate, would require 50/100*4.5 = 2.25 liters. So, what happened to the “missing” 2.25 liters? is that being consume dby the air bubble that has now been compressed to as small as it can go, but is still preventing any more ful being added?

All the above is bad enough. But it gets much worse. Here’s the actual gas receipt from the gas station, showing the actual fuel I managed to get into the tank at the station, PLUS the extra fuel I was able to add when I got home 1.4 km later.






The breakdown is as follows:

The pump nozzle “stopped” at 19.1 liters.

I managed to add another 0.18 liters using the top-up technqiues right at the gas station.

Then, when I got it home at 1.4 km, I managed to get another 0.47 liter in using the top-up techniques.

So, it took a total of 19.75 liters to get the fuel tank topped up to the same exact point as when it began the trip.

But 19.75 liters to cover 354 km means an average of 5.58 liters / 100 km, which given the processes used should really be rounded to one decimal place, not 2, so 5.6 L/100km.

But that is 5.6 actual versus the 4.5 from the TIS, which indicates that the TIS is understating the actual fuel consumption by just over 24% !!

That is, in U.S. terminology, the gas mileage is actually 42 mpg versus the TIS’s erroneous 52.3 mpg!

Which number do YOU believe? I find 42 mpg to be credible given the low 51 mpg cruising speed, moderate bidirectional wind conditions, and minimized stops and slow speed segments.

Note also that the 19.75 liters I added after the trip, plus the 1.26 liters still remaining given the remaining 28 km range before the fill-up, means that the tanks’ true apparent capacity would APPEAR to be 21 liters = 5.55 gallons , not 22.7 liters = 6 gallons.

I also learned how easy it is to accidentally cause the TIS to display completely untrue and mangled information. Any of the following actions will do it:

• Intending to add a destination and instead starting a brand new trip (easy to do)
• Intending to start a brand new trip and instead forgetting to REMOVE the existing trip, so getting an unintentional continuation of first trip statistics (also easy to do)
• Starting the above brand new trip, accidentally extending the existing trip instead, and wondering why even the start date for your new trip is a date prior to today. Maybe even showing a start date several days ago if you forgot to “end” your last trip and the TIS has faithfully continued to add km or miles you actually rode locally since the trip to that last trip
• Trying to understand what happened to the missing liters in the 22.7 liter fuel tank . . .

I’m going to continue to use the TIS, because MUCH of its information is still very useful on a trip:

• Time the trip was started
• Duration of the the trip so far
• Trip distance traveled so far (which DOES match the odometer, which matches Google Maps)
• Average speed (which is calculate correctly incorporating ALL stops whether short or long. This tells you what ACTUAL number of hours you need to ride yet today to reach that reserved hotel room)
• Compass indicator that shows your actual current direction of travel
• Trouble code icon and tire pressure screen

But for the fuel used, I will multiply the TIS erroneous number by 1.24 to get the REAL fuel used so far on any trip.

And for the average fuel consumption, I will multiply the average Liters/km number by 1.25 (Close enough to the actual 1.244 and MUCH easier to do the math mentally as “5/4”). For you U.S. guys, simply multiply your MPG number by 0.80 (which is the inverse of 1.24)

Jim G

 

After reading all that, my eyeballs are tired.

2114 RPM @ 51 MPH is not good for your engine. Should be at least 2800 RPM and better @ 3000 RPM which is the sweet spot for M8 engines.

All I can say is that you got Gremlins, yes Gremlins. Get someone to give you a Gremlin Bell and then just fill up the tank and ride without analyzing anything, your stress level will be lower and you just might enjoy the ride.

 

CoolBreeze, at 2100 rpm the RG3's engine is WELL on the torque curve. This is NOT "lugging" this engine, On the 50 mph to 60 mph roads I typically run on, to run at 2800 or 3000 I would need to break the local speed limits to stay in top gear. And going to a lower gear to increase the rpm just adds to the fricition losses, so the engine's efficiency would be notably lower. If the engine were a Twin Cam, it would be a differetn story, That Twin Cam engine, pushing along a 1160 lb trike would not be able to get out of its own way at 2100 rpm, and would definitiely need more rpm. But the M8 is fine at 2100.

Jim G