Gas mileage in the rain

[Mondo Limbo]

I get 5 to 7 mpg better when it's raining.  It's happened several times and that had to be it.  It's not because I'm riding slower or the cooler engine, I don't get this good mpg when riding slow with a group or riding in the cold weather.  Any ideas on why and what I might do to get the extra mpg all the time?

[tonyfan70]

Might not be riding slower, but I bet you are accelerating slower. Both from a stop and out of the corners.

[Hoser]

Might not be riding slower, but I bet you are accelerating slower. Both from a stop and out of the corners.

+1 Hoser 

[gordonv]

My thought was colder damp air, heats up and the steam adds more presure, giving more power, therefore you use less throttle.

The other about slower acceleration makes sense also, but that should be duplicatable.

[Bigwolf]

All of the possabilities mentioned so far are very likely.  There is, however, one other possability although maybe less likely.  Moisture in the intake air will help to eliminate some minor detonation.  If you are running stock ignition timing, then I would not expect this to be the difference.  However, if you are running advanced ignition, then you could be getting some minor detonation that is robbing some fuel economy and the moisture of the rain is eliminating that detonation.

Bigwolf

[JaysGone]

My thought was colder damp air, heats up and the steam adds more presure, giving more power, therefore you use less throttle.

The other about slower acceleration makes sense also, but that should be duplicatable.

I believe you are more then likely correct.
Cooler damp air will always add mileage and a bit more power to any carbed engine.
Not so true with FI.

[olddog1946]

I believe the official name for that is Volumetric Efficiency , much better in colder/damp atmosphere.

[WamegoRob]

So it'd be interesting to hear from Seattle and Phoenix folks comparing mpg's.

[garyheskett All 49 x 3 st.louis]

Wow, I was hoping to get through a day without feeling "stupid". Well, another day I didn't make it with "volumetric efficiency".  Oh well, the rain comes off the windshield a lot better at 80+ mph!!!  I guess the mpg goes down though!!!

[98valk]

My thought was colder damp air, heats up and the steam adds more presure, giving more power, therefore you use less throttle.

The other about slower acceleration makes sense also, but that should be duplicatable.

I believe you are more then likely correct.
Cooler damp air will always add mileage and a bit more power to any carbed engine.
Not so true with FI.

that means its running too rich the rest of the time. its cold air (denser with more oxygen) not dampness/water in the air,
Hmmm, volumetric efficiency?, more moisture in the air means less actual air with oxygen. less oxygen means a weaker burn, reason high humidity kills power.
water injection for race engines makes power for other reasons.

And yes FI, the O2 sensor puts it back to too rich, so the cat will work like it always does wasting fuel.

[sandy]

So it'd be interesting to hear from Seattle and Phoenix folks comparing mpg's.

Here in AZ it's well known that on a cool damp day in the winter, any vehicle feels like it's running better and has more power. The HOT DRY days and everything feels a bit more sluggish.

[ricoman]

So it'd be interesting to hear from Seattle and Phoenix folks comparing mpg's.

Here in AZ it's well known that on a cool damp day in the winter, any vehicle feels like it's running better and has more power. The HOT DRY days and everything feels a bit more sluggish.

It only makes sense.
My 10 yr. dog acts like a puppy in cool weather.
Come to think of it, so do I!

[X Ring]

My understanding is the cooler, denser air can hold more fuel which provides more power; therefore, you use less throttle.

Marty

[Moonshot_1]

You start with a single gallon of gas.
You have an average mpg of say 35 mpg.
The suggestion is that you can go an extra 5 miles on the gallon because of atmospheric conditions? That's 25 extra miles per tank in the rain?

Just can't see that.

I can see the reduced speed, reduced acceleration (the big factor) and the less aggressive riding style that accompanies inclement weather having exactly that impact on MPG though.

[CajunRider]

Funny... I usually loose mileage in the rain... usually cause I keep wrapping the trottle all the way to the stop...

The Valk "power slides" like a dream!!!!    

[O-B-1]

So it'd be interesting to hear from Seattle and Phoenix folks comparing mpg's.

Phoenix versus Biloxi, MS.... Biloxi seems to have like 95% humidity...

[98valk]

you are riding slower in the rain, unless u have a deathwish.
are using less throttle from a stop in the rain.
pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.
did u experience a tail wind on your trip?

Truck Route and Terrain: East/west routes experience almost continual crosswinds and head winds. Less fuel can be used on north/south routes where parts of the trip are not only warmer but see less wind resistance.

http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

[ricoman]

pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.


http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

heat pushes the piston down?
The rapid burning of the fuel does not? Heat is a by product of the burning fuel.
You quote a study by a deisel engine manufacturer dealing with semis. Do you really believe cooler oil or rear differential temps on a motorcycle will have an effect on mileage? A motorcyle weighing maybe 2% of what a loaded semi weighs? Just how much water does a bike have to push to reduce the mpg, equal to the parting of the Red Sea?
There are very minimal similarities between the operation of a gas powered 800 lb motorcycle and a semi & trailer weighing 80,000 lbs with a deisel engine.
Apples to oranges for sure.

[John U.]

Make that 1/10 of one percent: 800 divided by 80,000= .01
Still some of CA's statements hold true regardless of gross weight or gas vs. diesel.
Cold, damp air is denser, this makes the engine run better in my experience but it is harder to push out of the way.
A cooler engine will run less eficiently, within certain parameters.
Some water will need to be pushed out of the way, if the road has wheel troughs it maybe enough water to make a difference.
Against all that is the positive effects on gas mileage of riding slower and more gentle use of the throttle so as not to break traction.
So, all we need to do a valid comparison test is a dyno, a wind tunnel and several guys with a fire hose. 

[CajunRider]

Can I volunteer to man the fire hose??    

[Valkpilot]

pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.


http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

heat pushes the piston down?
The rapid burning of the fuel does not? Heat is a by product of the burning fuel.
You quote a study by a deisel engine manufacturer dealing with semis. Do you really believe cooler oil or rear differential temps on a motorcycle will have an effect on mileage? A motorcyle weighing maybe 2% of what a loaded semi weighs? Just how much water does a bike have to push to reduce the mpg, equal to the parting of the Red Sea?
There are very minimal similarities between the operation of a gas powered 800 lb motorcycle and a semi & trailer weighing 80,000 lbs with a deisel engine.
Apples to oranges for sure.

Actually, I believe that most of the influences CA states will be magnified on a smaller, lighter vechicle.

[tonyfan70]

If the water splashing on the oil pan and rear end is cold enough to make the oil thicker to the point of affecting mileage in a noticeable way...I have to ask....

How cold is the cursed rain you're riding in?

Maybe the mileage gains are from not using the throttle...because your arm is frozen solid.

[98valk]

pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.


http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

heat pushes the piston down?
The rapid burning of the fuel does not? Heat is a by product of the burning fuel.
You quote a study by a deisel engine manufacturer dealing with semis. Do you really believe cooler oil or rear differential temps on a motorcycle will have an effect on mileage? A motorcyle weighing maybe 2% of what a loaded semi weighs? Just how much water does a bike have to push to reduce the mpg, equal to the parting of the Red Sea?
There are very minimal similarities between the operation of a gas powered 800 lb motorcycle and a semi & trailer weighing 80,000 lbs with a deisel engine.
Apples to oranges for sure.

physics is physics,  it doesn't change,

1 lb of lead falls to the earth the same speed as 1 lb of paper.

did u ever ride a bicycle thru a puddle, did u ever notice the reduction in speed?, and that is with a thin tire.
there are many papers written on the affect weather has on MPG.

[RP#62]

physics is physics,  it doesn't change,

1 lb of lead falls to the earth the same speed as 1 lb of paper.

did u ever ride a bicycle thru a puddle, did u ever notice the reduction in speed?, and that is with a thin tire.
there are many papers written on the affect weather has on MPG.

Only in a vacuum.

-RP

[ricoman]

pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.


http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

heat pushes the piston down?
The rapid burning of the fuel does not? Heat is a by product of the burning fuel.
You quote a study by a deisel engine manufacturer dealing with semis. Do you really believe cooler oil or rear differential temps on a motorcycle will have an effect on mileage? A motorcyle weighing maybe 2% of what a loaded semi weighs? Just how much water does a bike have to push to reduce the mpg, equal to the parting of the Red Sea?
There are very minimal similarities between the operation of a gas powered 800 lb motorcycle and a semi & trailer weighing 80,000 lbs with a deisel engine.
Apples to oranges for sure.

Actually, I believe that most of the influences CA states will be magnified on a smaller, lighter vechicle.

let's see, a Valk rear end contains 150cc (.159 qt) of fluid. A typical semi rear end contains 7-10 qts. Can't quite see temp affecting them the same.
I would think cold rear end fluid in that amount would be a bit harder to get moving.
A Valk engine has about 4 qts of fluid. A valk has no separate tranny fluid.
A semi tractor has 15-20 qts. in the engine and 12 - 30 qts. in the tranny, thats 27-50 qts. of lube vs 4.
Could 4 cold qts. of fluid vs 27-50 qts. be as hard to get moving when cold?
I just cannot see a valid comparison. Nor do I see a magification of the problem because of the Valk being lighter.

[Gryphon Rider]

Make that 1/10 of one percent: 800 divided by 80,000= .01

Hmmmm... Ricoman guesses 2%, then figures a Valk weighs 800 lbs and a tractor-trailer weighs 80,000 lbs.  Based on his figures, he's only out by a factor of 2.  Then John U. corrects him by saying 0.01 means 1/10 of one percent when actually 0.01 means 1%, making his number 1/10 of the correct answer, an error factor of 10.  Whatever happened to the book-reading emoticon we had on the old board?  

[ricoman]

Make that 1/10 of one percent: 800 divided by 80,000= .01

Hmmmm... Ricoman guesses 2%, then figures a Valk weighs 800 lbs and a tractor-trailer weighs 80,000 lbs.  Based on his figures, he's only out by a factor of 2.  Then John U. corrects him by saying 0.01 means 1/10 of one percent when actually 0.01 means 1%, making his number 1/10 of the correct answer, an error factor of 10.  Whatever happened to the book-reading emoticon we had on the old board? 

who has time to read?
too busy on the net.
(I can do the math (not algebra though), was in a hurry.

[Valkpilot]

pushing water requires more throttle
hitting puddles reduces speed requiring more throttle.
cold water hitting the rear diff makes the oil thicker
cold water hitting the bottom of engine cools the engine, a cold engine/oil makes less power, heat is what pushes the piston down, plus thicker oil.
cooler ambient air temps are denser air, pushing a vehicle through denser air reduces mpg.


http://cumminsengines.com/assets/pdf/Secrets%20of%20Better%20Fuel%20Economy_whitepaper.pdf

The Physics of MPG

heat pushes the piston down?
The rapid burning of the fuel does not? Heat is a by product of the burning fuel.
You quote a study by a deisel engine manufacturer dealing with semis. Do you really believe cooler oil or rear differential temps on a motorcycle will have an effect on mileage? A motorcyle weighing maybe 2% of what a loaded semi weighs? Just how much water does a bike have to push to reduce the mpg, equal to the parting of the Red Sea?
There are very minimal similarities between the operation of a gas powered 800 lb motorcycle and a semi & trailer weighing 80,000 lbs with a deisel engine.
Apples to oranges for sure.

Actually, I believe that most of the influences CA states will be magnified on a smaller, lighter vechicle.

let's see, a Valk rear end contains 150cc (.159 qt) of fluid. A typical semi rear end contains 7-10 qts. Can't quite see temp affecting them the same.
I would think cold rear end fluid in that amount would be a bit harder to get moving.
A Valk engine has about 4 qts of fluid. A valk has no separate tranny fluid.
A semi tractor has 15-20 qts. in the engine and 12 - 30 qts. in the tranny, thats 27-50 qts. of lube vs 4.
Could 4 cold qts. of fluid vs 27-50 qts. be as hard to get moving when cold?
I just cannot see a valid comparison. Nor do I see a magification of the problem because of the Valk being lighter.

"Lighter" was perhaps the wrong word to use.  More correctly, the Valk has lots less mass, and therefore will react faster and more profoundly than a larger vehicle to the same inputs of wind resitance, water resistance, cool rain, etc.

[John U.]

Make that 1/10 of one percent: 800 divided by 80,000= .01

Hmmmm... Ricoman guesses 2%, then figures a Valk weighs 800 lbs and a tractor-trailer weighs 80,000 lbs.  Based on his figures, he's only out by a factor of 2.  Then John U. corrects him by saying 0.01 means 1/10 of one percent when actually 0.01 means 1%, making his number 1/10 of the correct answer, an error factor of 10.  Whatever happened to the book-reading emoticon we had on the old board?  

Quite right Gryphon Rider, I have no excuse, except it was late.