Looking at all the MPG threads... I think I figured out why mine is lower than so many others.

My speedo is corrected so if my bike say's 75 it's really going 75. It use to be showing like 83 when going 75 so when I checked the mileage it looked like I was getting way more out of a tank.

So, before you start bragging about your MPG's fix your Harley speedo that always reads fast from the factory.

 

How did you correct it, and how did you confirm speedo is displaying actual MPH?

 

On my 2011 RGU I confirmed the speedo was off by setting the cruise for 60 mph and noting that my aftermarket (you cannot do this with a Boom system) GPS read 57 mph. I did this several times. I then fed that into my Thundermax software and from then on my speedo was accurate to < 1 mph.

 

Corrected my '09 in the tune settings with WinPV/Power Vision, confirmed with a Garmin GPS

 

I'm curious if the PCM logs the miles and the speed the same way. Does it record the distance correctly but display the speed in 'man inches'?

That's a thought that has bounced around my head for a long long time about a few different vehicles. I once owned a VW Jetta that had an optimistic speedometer.

 

I wonder how accurate interstate mile markers are? Shortly after purchasing my 2018 FLHXS (minimal tire wear), I stopped next to a mile marker, and reset one of my trip meters to zero. One hundred mile markers later, I stopped again. Trip meter displayed 100.8 miles. This led me to believe the factory calibration was fairly (better than 99%) accurate. Thoughts?

 

Speedometers are usually set by manufacturer at 2 mph faster than actual speed in the US. This is on new vehicles. As things wear like tires it changes. But other factors later on can make them way off. A GPS will give you accurate speed that you can check how for the speedometer is off. You can also get on a interstate or highway with mile markers and a stop watch and time yourself from miles marker to mile marker at 60 mph it should take you 60 seconds, 2 miles at 60 mph will take 120 seconds, etc. A buddy with a radar will give you an accurate speed if head on and will show your speed slower as the angle of approach is increased.

 

In my experience as it applies to touring models; In 2015, the speedometer accuracy from the factory calibration improved greatly. 2014 and earlier bikes were about 6% optimistic. My 2015 and 2018 have been very accurate when measured using stand-alone GPS units. I calibrated my 2011 before those.

 

I ride by RPM, surrounding conditions and feel, and gas up when necessary. That said, I did correct my speedo using my TTS so that it was in line with what the Garmin Zumo said.

 

Can early model (2002) efi touring models be adjusted also using a Power Vision? New to the efi thing.