BMW RT Pilot
Premier Member
And I always thought cooler, denser air was good for power production.
2016 RT greatly reduced mileage in cold weather
- Thread starter BMW RT Pilot
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JAVGuzzi
Premier Member
It is, but not for drag. And several Riders have claimed they get better mileage at higher altitudes than at lower altitudes, and I believe that, even tho at a higher altitude, less power can be produced. I don't understand why a higher altitude should give better gas mileage, except for the thinner air and less drag.
BMW RT Pilot
Premier Member
I need a drink. Lots of drinks.
Rolling resistance of the different kinds of pavement could make a difference as well. On Guam, where they used coral as a substrate and the travel paths are polished glass smooth, the roads have little resistance to anything. Whereas the highways in southern Nevada seem to be extremely rough beause they chew up a set of tires in no time and a tank of fuel doesn't seem to last nearly as long. (Yah, that's my story and I am sticking to it...)
Because of the reduced O2 density the O2 sensor tells the computer "there is less air, use less fuel to maintain the correct Air/Fuel mixture".
Mostly it's about drag. Keep in mind as speed doubles, drag quadruples. The drag at 50mph is four times the drag at 25mph and the drag at 100mph is four times the drag of 50mph. This is why "dyno" speeds are not reflective of what you can expect on the track.
JAVGuzzi
Premier Member
Ya, but I have read that bikes with carbs also get better mileage at higher altitudes.
DrNeo
Premier Member
Technically at the altitudes that we ride, it's the pressure that isn't as high - O2 concentrations are the same, but as you said, the density has changed. Big pet peeve of one of my undergrad professors
Technically at the altitudes that we ride, it's the pressure that isn't as high - O2 concentrations are the same, but as you said, the density has changed. Big pet peeve of one of my undergrad professors
True, the ratio doesn't change, but for a given volume of air there will be fewer molecules of every gas. Including O2. As for altitudes, I've been at altitudes on the bike where the FAA requires me to be on supplemental oxygen while flying....
I, too, get worse mpg in the winter on my 05 gs1200. I mostly suspect that the fuel program for the bike takes the temp and decides that the cool weather requires a certain level of enrichment not needed in warmer temps. And there is nothing the owner can do about that which would seem worthwhile. Use a thermostat rated for 200 as opposed to 180 degrees? The cardboard over the radiator might work if the rider was willing to make the hole adjustable and remember to remove it before the engine overheated on warm days? Paying attention to the bike's engine temp gauge would be a useful skill. I doubt that warmer plugs would help if the bike will start on reg temp plugs. That might work on some air cooled bikes. But I have my doubts if the engine is liquid cooled? The bike warms up to operating temp or it doesn't. MY GS temp gauge never varies by so much as one bar regardless of ambient temp after the bike warms up. Granted, I let the bike idle a little more in winter so that the heated grips get started before I have to get moving. If you are running electric gear and slowly commuting, maybe the bike uses more fuel to keep the voltage up?
My suspected guess is ambient 55F is where my enrichment hits. Above that, I get 240/tank. Below that I am lucky to get 210. As I get down to 20F, I might get 180-190 out of a tank at commuter speeds.
For every bit of automated/programmed stuff by the manufacturer, there is a trade off. Stuff that works perfectly in the state of the manufacturer works less so everywhere else. As an example: HD's auto-cancelling turn signal program works damn good here. My GS system nearly kills me several times per week. It either quit way too soon or stays on way too late and it rarely gets close most of the time. Makes one wonder how good the rest of the computer programming is? My first hint of things to come was noting that the clock did not keep good time. A $3 timex digital from the discount bin at the local drugstore out performed the factory unit by whole minutes over 6 months.
My suspected guess is ambient 55F is where my enrichment hits. Above that, I get 240/tank. Below that I am lucky to get 210. As I get down to 20F, I might get 180-190 out of a tank at commuter speeds.
For every bit of automated/programmed stuff by the manufacturer, there is a trade off. Stuff that works perfectly in the state of the manufacturer works less so everywhere else. As an example: HD's auto-cancelling turn signal program works damn good here. My GS system nearly kills me several times per week. It either quit way too soon or stays on way too late and it rarely gets close most of the time. Makes one wonder how good the rest of the computer programming is? My first hint of things to come was noting that the clock did not keep good time. A $3 timex digital from the discount bin at the local drugstore out performed the factory unit by whole minutes over 6 months.
Alas, my dealer assures me mightily that the feature cannot be turned off. Granted, I did not seek a second opinion. Even though my ower's manual reads like the feature can be turned off, my dealer does not read it the same way. Anybody got better info should post it up?
BMW RT Pilot
Premier Member
And as to prove a point, on my latest ride, with the temps in the low-90s, I could've hit anywhere between 250-265 miles on a tank @ 85 mph.
BMW RT Pilot
Premier Member
My last ride took me through TN, AL, MS, TN (again), AR, OK, KS, and CO (and then back!). Temps ranged from the upper 80s to mid 60s. Range on the tank was between 260 (based on how much fuel was still in the tank after a filling) to just over 200.