Increase in MPG in colder weather
#11
11-17-2018, 05:18 PM
Banned
That is the fact of the matter once the math is figured out.
It takes more electrics to recharge and longer. (read bigger drag from the alternator )
The engine is in a more viscous fluid.
Along with all this, it takes a much fatter AFR to make a cold engine run.
So this anomaly falls on the math failure somewhere.
#13
11-17-2018, 07:39 PM
Here's just some examples (all highway miles) of what's been happening. I know I've done some rounding off but that wouldn't account for a 10 mpg difference
115.3 / 3.27 = 35.26
140.2 / 4.0 = 25.05
105 / 2.33 = 45.0
122 / 2.7 = 45.18
135.3 / 3 = 45.1
I should've said in the OP, I'm not complaining about the better cold temp mpg. I do however wish that it would get the better mpg in the summer when I do 98% of my riding.
Since the bike is new to you, I would suspect an error in computing MPG by the previous owner or a recent change of which you are unaware. Most of the factors reducing MPG in cold weather have been mentioned, but not mentioned was increased viscosity of lubricants. Engine oil reaches almost the same temperature in cool weather as in warm weather but wheel bearings have no combustion near them to heat them up so they stay cooler in cool weather than in warm so there is more resistance to movement in the grease. The same is true to a lesser extent to the primary case and transmission, as they are both warmed by contact with the engine, but less so in cool weather vs hot weather.
They all will.
That is the fact of the matter once the math is figured out.
It takes more electrics to recharge and longer. (read bigger drag from the alternator )
The engine is in a more viscous fluid.
Along with all this, it takes a much fatter AFR to make a cold engine run.
So this anomaly falls on the math failure somewhere.
That is the fact of the matter once the math is figured out.
It takes more electrics to recharge and longer. (read bigger drag from the alternator )
The engine is in a more viscous fluid.
Along with all this, it takes a much fatter AFR to make a cold engine run.
So this anomaly falls on the math failure somewhere.
If the air is denser in the cold temps, and less dense in the warmer temps, could the EFI possibly not be compensating for this, and causing it to run too rich in the summer?
Last edited by Long lonesome highwayman; 11-17-2018 at 07:41 PM.
#14
11-17-2018, 09:44 PM
Seasoned HDF Member
There's a scientific explanation for why you use less fuel in warmer weather, and it's to do with air temperature.
As you may know, your engine uses air, as well as gas, in order to generate energy. In fact, it uses huge amounts of the stuff, though only the oxygen is used in combustion. These oxygen molecules combine with carbon in the fuel during combustion, to form--you guessed it, carbon dioxide.
Anyway, one property of air, like many substances, is that it expands when it warms. This makes it less dense--molecules of the various gases are spread further apart. This means that every gulp of air your car is taking during combustion has less oxygen in it at warmer temperatures, and if there's less oxygen, the engine compensates by using less fuel.
This is bad from a power perspective, but good for economy. The engine is combusting less fuel due to the warm air, improving fuel economy. During winter, the reverse is true--denser air encourages the engine to chuck in more fuel, boosting performance and harming economy
randy
As you may know, your engine uses air, as well as gas, in order to generate energy. In fact, it uses huge amounts of the stuff, though only the oxygen is used in combustion. These oxygen molecules combine with carbon in the fuel during combustion, to form--you guessed it, carbon dioxide.
Anyway, one property of air, like many substances, is that it expands when it warms. This makes it less dense--molecules of the various gases are spread further apart. This means that every gulp of air your car is taking during combustion has less oxygen in it at warmer temperatures, and if there's less oxygen, the engine compensates by using less fuel.
This is bad from a power perspective, but good for economy. The engine is combusting less fuel due to the warm air, improving fuel economy. During winter, the reverse is true--denser air encourages the engine to chuck in more fuel, boosting performance and harming economy
randy
#15
11-18-2018, 07:20 AM
Correction: in my previous reply I posted some results that I've been getting in warm and cooler weather. One of those results was
"140.2 / 4.0 = 25.05"
It should be 35.05, not 25.05. The error was not made in the calculation, it was made in posting the result online. (hit the wrong key and didn't realize it I guess)
The bolded is what I'm suspecting but does anyone know why I would be running a better AFR now than before? Could something be wrong with the EFI? Should it be retuned in the summer for better results?
"140.2 / 4.0 = 25.05"
It should be 35.05, not 25.05. The error was not made in the calculation, it was made in posting the result online. (hit the wrong key and didn't realize it I guess)
Originally Posted by Kingglide549 
I would attribute it to bad math somewhere.
It takes more fuel to run at colder temps to start.
The DA is denser in cold weather...everything is working against better mileage..
The only possibility you are running a better AFR now.
It takes more fuel to run at colder temps to start.
The DA is denser in cold weather...everything is working against better mileage..
The only possibility you are running a better AFR now.
The bolded is what I'm suspecting but does anyone know why I would be running a better AFR now than before? Could something be wrong with the EFI? Should it be retuned in the summer for better results?
Last edited by Long lonesome highwayman; 11-18-2018 at 07:27 AM.
#17
11-18-2018, 12:03 PM
#20
11-18-2018, 03:55 PM
Elite HDF Member
There is also the difference in the fuel winter to summer.
The 2% energy difference doesn't account for all the difference but factoring in the things others have mentioned you can start to get closer to the difference.
A couple of weeks ago I went for about a 300 mile ride. It never got over 45 degrees and the oil temp never got over 170. I don't know at what temp the ecm goes to closed loop but I understand it runs open loop till the engine is "warm". More time open loop, pouring fuel into the engine, would drop milage as well I would think.
Despite those higher prices, summer gasoline contains about 1.7 percent more energy than winter gasoline. Warmup times aside, that’s why you could measure reduced fuel economy outside the summer months. Winter gasoline varies widely in volatility throughout the season. Refiners constantly adjust their RVP to as high as 15 psi—higher than sea-level atmospheric pressure, which is 14.7 psi—to help the gasoline ignite more easily in colder temperatures. The vapor pressure varies by month, region, and octane. In frigid temperatures, higher-volatility fuel is essential and does not cause the smog effect it would in the summer. Using low-RVP fuel is a nonstarter in freezing weather; the engine won’t turn over or might misfire
A couple of weeks ago I went for about a 300 mile ride. It never got over 45 degrees and the oil temp never got over 170. I don't know at what temp the ecm goes to closed loop but I understand it runs open loop till the engine is "warm". More time open loop, pouring fuel into the engine, would drop milage as well I would think.