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normal operating temp and mpg?


jeffro7172

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The real answer is....

Humidity, Temperature, and Barometric pressure.

As Humidity goes up, engines get richer,

As temps go up, engines get richer,

And as Baro's go up, engines get Leaner.

Colorado air is Very Dry. A lot of high elevation air is Multiplication Drier than lower elevation air. Take for instance right now... it's 23% humidity here in Colorado, and in Oklahoma 48%, and in Florida it's 92%.

This means there's almost twice as much oxygen being displaced by humidity in Oklahoma, and almost 3.5 time as much being displaced in Florida.

There's you big numbers, that account for the big AFR & MPG differences.

And yes you're spot on about one thing...

engines should really be mapped at elevation !

PS. I get stupid good gas mileage in West Texas as well..... why, because it's Dry, and there's lots of pressure. ( but you don't have to believe just me, ask Stan how I was riding in Texas, and I was still getting mid 40's mpg....Or Ask Jay how I was riding in western Colorado... and averaging 47mpg.)

:icon_biggrin:

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Well,I`m not questioning that your mapping is vastly better then O.E.M. in regard to fuel economy.

Humidity only matters in high temperatures,at 80 F deg saturation % of water is 3.3%,90-4.7%,100%-6.5%,etc

So, if it is 80 F deg and 100% humidity the engine will run only 3.3% richer vs dry air, it very rarely gets that warm at 10000-11000 ft, in any case it is still 3.3% in worst case scenario.

Can`t explain 10-20 mpg % gain.

The formula for corrected air pressure CAM=UMP-(SPxRH/100)xinches of Hg,

CAP-corrected air pressure

UMP-uncorrected baro pressure

SP-saturation pressure for given temperature

RH-relative humidity in % .

You know,never bikes and pretty much all the cars run in closed loop during cruise mode,they are immune to a/f variations vs elevation,somehow still get better mpg at elevation,,, :icon_wink:

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Well I always thought that it's a little bit of everything that gets multipled together, in order to account for the Large differences.

With that said... I also always thought that the biggest factor in my higher mileage was Air conditions and combustion. I also knew that Aerodynamics plays a Huge, Huge, Huge part on the top speed of a Bike, but did not give it that much warrant for speeds below 70 mph.

I like charts.

psychrometric_chart_29inHg.pdf

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Well, I just learned something new....

Atmospheric Pressure at 6000 feet is... 0.78461 that of sea level.

Atmospheric Density on the other had is... 0.82168 that of sea level.

Interesting...... very, well to me anyways.

Edited to add:

So what does this mean.... it means I was right, and Tomek was right, which means I was wrong... sort of.

My argument was that the Air Was better Molecule wise at altitude, due in part to the dryness multiplied against the oxygene content of the air. Since its was my understanding that Humidity displaces the Oxygene faster than the Nitrogen, but I won't go there.

Tomek was stating the Aero drag was so much less. I thought, that the aero drag and density of the air were proportional. Meaning that as you lost Aero drag due to the decreased pressure of the air on the bike, that you also lost the combustion chamber content at the same rate, due to the loss of pressure filling the cylinder and I thought the Density was the same percentage loss as the pressure.

Which means.... the air is content is better at altitude. More Oxygen.

Which means....Aero Drag is Far less at Altitude. Proportional to Density.

Which means I was wrong.....

But now I'm smarter for it. I like that.

Thanks Tomek.... that was fun. :icon_biggrin:

ps. Thanks Stan, had we not talked, I would not have gone looking for the relationship of Density to Pressure at Altitude. :icon_biggrin:

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OH now wait again....

I was reading at lunch about atmospheric density and Aerodynamic drag... and well, now I think I'm on information overload.

Mud maybe...

What I do know is this... I've got some studying to due.

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OK after a Long bit of studying, a lot of very dry reading.... I have got some info to post, and have come to a different decision entirely.

First I read most of the ISA... which is the 1976 International Standard Atmosphere. Holly Crap is that thing Dry to read.

OK. back on target.

First off we must accept some sort of numbers to compare, geographical Atmospheric data, something that's not made up, and can be proven beyond a shadow of a doubt. For this I used WeatherUnderground history data, which is readily accessible.

Then I had to find a Calculator that was, not of my math ( so it would take my possible error out of the equation), and had all of the variables needed to accurately determine Relative HP, and Relative Density.

Then I had to choose to places as a comparison. How about Tampa, Fl. and Castle Rock, Co.. Then I had to find out there geographical and atmospheric data to compare.

Hmmmm... then I had a thought, I can't just compare any one given month, because some months maybe differ from the average for a given area. So I decided to use an entire years averages.

Here's the Results:

Tampa, Fl.

Average Temp.............. 73 deg. F.

Average Humidity............... 75.7%

Average Pressure......... 30.03 inHg

Elevation........................... 30 Ft.

Relative HP........................ 101%

Relative Air Density............. 96.9%

Castle Rock, Co.

Average Temp............48.6 deg. F.

Average Humidity............... 50.9%

Average Pressure......... 29.91 inHg

Elevation........................6,300 Ft.

Relative HP........................ 80.2%

Relative Air Density............. 80.6%

So what does this mean......

Tomek and I were both wrong !

There's more relative HP and less Aerodynamic Drag at Lower elevations than there is at Higher elevations.

(Aerodynamic drag is a Calculation of Air Density.)

So there you have it. :icon_neutral:

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Here's the Results:

Tampa, Fl.

Average Temp.............. 73 deg. F.

Average Humidity............... 75.7%

Average Pressure......... 30.03 inHg

Elevation........................... 30 Ft.

Relative HP........................ 101%

Relative Air Density............. 96.9%

Castle Rock, Co.

Average Temp............48.6 deg. F.

Average Humidity............... 50.9%

Average Pressure......... 29.91 inHg

Elevation........................6,300 Ft.

Relative HP........................ 80.2%

Relative Air Density............. 80.6%

So what does this mean......

Tomek and I were both wrong !

There's more relative HP and less more Aerodynamic Drag at Lower elevations than there is at Higher elevations.

(Aerodynamic drag is a Calculation of Air Density.)

So there you have it. :icon_neutral:

I`ve fixed that for you,since when denser air equals less aero drag ? :icon_duh: C`mon dud, is it easier to run in the water ?

Fd =1/2puuCdA

where

Fd is the force of drag

ρ is the mass density of the fluid,

u is the velocity of the object relative to the fluid,

A is the reference,surface area

Cd is drag coefficient

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RELATIVE to themselves at each Location, was how I was looking at it.

Relative Aerodynamic Drag..... relative to the HP.

There's 4.1% Less Aerodynamic Drag in Florida, relative to the HP in Florida.

Then there's 0.4% More Aerodynamic Drag in Colorado, relative to the HP in Colorado.

Now on the other hand..... Let's look at again in a different way.... this time let's Comparing the numbers directly...

HP to HP.... there's 20.8% Less HP in Colorado @ 6300 ft. elev. compared to the Florida location.

Cd to Cd... there's 16.3% Less Aerodymanic Drag in Colorado @ 6300 ft. elev. compared to the Florida location.

This means here in Colorado at 6300 ft. we have 79.2% of the HP and 83.7% of the Cd.

For an overall difference of 4.5%.

(that's LESS HP relative to Aerodynamic Drag in Colorado, comparing the 2 locations and data.)

...

Now maybe the Cd - HP relationship is not linear...... ? Doubtful .... but hey I've learned, a lot this week, so why don't you explore that side of it and tell me what you find.

I didn't try that angle.

...

Oh and buy the way, here's the online Calculator I used....

http://wahiduddin.net/calc/calc_hp_dp.htm

There's a lot of great info and explanations on his site.

:icon_confused:

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After reading your post,honestly WTF ?

I though we were discussing here fuel consumption at elevation vs sea level.It has everything to to with aero drag in absolute terms.

Whether there is more or less hp relative to relative aero drag has nothing to do with fuel consumption,it matters as far as Vmax ,less aero drag,less hp,but rolling resistance is the same so in the end Vmax at elevation is less.

Example,if at see level total drag splits 30% rolling resistance and 70 % aero for given speed ,at 6000 ft aero drag will decrease by 20 %,rolling will be the same, total will decrease to 86% of what it was at the see level.But you`ll have only about 80% of hp,that is why Vmax will be lower and acceleration much weaker.

Anyway,that is totally different subject.

I don`t need to explore this nonsense any further,I had at least couple of semesters of vehicle dynamics and fluid dynamics back in school many moons ago,,,,,,,,,,

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Eric, the confusion here is that you are talking about two different issues. Tomek is only talking about drag versus altitude, the nature of the air composition is not likely to be too important.

Most of what you are talking about is the engine's volumetric efficiency, not thermodynamic efficiency, and only affects the peak power which can be produced. What fuel is consumed for a given output power will set the mileage term, and this is the question at hand.

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Eric, the confusion here is that you are talking about two different issues. Tomek is only talking about drag versus altitude, the nature of the air composition is not likely to be too important.

True.... sort of.

The confusion here is in the communication.

I was working on the goal of understanding all of the possible condition changes that would affect MPG increase at altitude.

I am open to any and every possibility, and believe it's all of the contents that make up for the difference. The Soup, if you will, has changed and therefore the ingredients must have changed as well.

...

Here's another ingredient for you "Fuel", Is low altitude Fuel the same as High altitude Fuel..... No !

...

Tomek.... relax Dude. I'm working with you.... Not against you.

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Here is another analogy:

It takes a certain amount of power to move a given object, a given distance in a given span of time. This is known as "Work". When cruising down the highway (not at max power) at sea level, you are making "X" amount of MPG. Cruising at the same speed at 6000', the air is thinner, so less drag which means more MPG.

I don't think it can get any more simple than that.

One thing I do know: At last years West Coast Bash in Montrose, I went 191 haul'n ass miles on 5.2 gallons of gas. :icon_eek: I don't think I could do that at 1000' elevation unless I kept it under 55 MPH.

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Eric, the confusion here is that you are talking about two different issues. Tomek is only talking about drag versus altitude, the nature of the air composition is not likely to be too important.

True.... sort of.

The confusion here is in the communication.

I was working on the goal of understanding all of the possible condition changes that would affect MPG increase at altitude.

I am open to any and every possibility, and believe it's all of the contents that make up for the difference. The Soup, if you will, has changed and therefore the ingredients must have changed as well.

...

Here's another ingredient for you "Fuel", Is low altitude Fuel the same as High altitude Fuel..... No !

...

Tomek.... relax Dude. I'm working with you.... Not against you.

Well,it depends,I`ve been known for trailering bikes from Chicago to Cheyenne on more then one occasion,so typically those trips start on Illinoiz fuel.

I have rather short fuse in some areas of my character. :icon_twisted:

Here is the last thing missing in this puzzle,engine specific fuel consumption. http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

Let`s use my example from above,if you decrease load by 14% for given rpm you`ll move from one BSFC zone to the other one,engine might be more efficient or less efficient,it depends,although realistically in case of XX motor it will be somewhat less efficient, at least in normal speeds range.

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Very Good.

I have a very long fuse most of the time, and can take a lot of venting, especially if I think the situation is worth my time. In this case, I believe the topic at hand is not only valuable to me, but for a lot of others on this board as well. So... I'll continue.

I like you're posting and reference, and have long known about an engines thermodynamic relationship to peak torque, and hence it's optimum fuel efficiency. But how to calculate an engines BSFC... I did not know. Ahhhhh... more to learn. I like that.

I'll play with that when I get a chance... and reply more later.

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Here is another analogy:

It takes a certain amount of power to move a given object, a given distance in a given span of time. This is known as "Work". When cruising down the highway (not at max power) at sea level, you are making "X" amount of MPG. Cruising at the same speed at 6000', the air is thinner, so less drag which means more MPG.

I don't think it can get any more simple than that.

One thing I do know: At last years West Coast Bash in Montrose, I went 191 haul'n ass miles on 5.2 gallons of gas. :icon_eek: I don't think I could do that at 1000' elevation unless I kept it under 55 MPH.

In science you know you develop a theory and then test it. Keeping the other factors the same (this is the hard part), you change the altitude and measure the mpg.

BTW - In classical mechanics, work is not done on a body in a straight line at constant speed (body in motion stays in motion unless acted upon by a force). The distance they are talking about is a force applied at a distance like one pound at a distance of one foot (a foot pound of torque) not 37 miles down a level highway in a given time.

In our imperfect world, there is work done in overcoming friction (engine, chain, tires, etc.) and drag (small at 55mph to huge at 155mph). There is also inefficiencies in the engine especially at low throttle setting that sap mpg that may change at altitude even more than drag does. You may be able to calculate it all, but back to the original point, you would still have to measure it to see if you were correct so why not just measure and forget all the theories and calculations?

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In science you know you develop a theory and then test it. Keeping the other factors the same (this is the hard part), you change the altitude and measure the mpg.

BTW - In classical mechanics, work is not done on a body in a straight line at constant speed (body in motion stays in motion unless acted upon by a force). The distance they are talking about is a force applied at a distance like one pound at a distance of one foot (a foot pound of torque) not 37 miles down a level highway in a given time.

In our imperfect world, there is work done in overcoming friction (engine, chain, tires, etc.) and drag (small at 55mph to huge at 155mph). There is also inefficiencies in the engine especially at low throttle setting that sap mpg that may change at altitude even more than drag does. You may be able to calculate it all, but back to the original point, you would still have to measure it to see if you were correct so why not just measure and forget all the theories and calculations?

Also a very good post... the whole thing, but, I especially like what I put in Bold.

Oh the fun.

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Here is another analogy:

It takes a certain amount of power to move a given object, a given distance in a given span of time. This is known as "Work". When cruising down the highway (not at max power) at sea level, you are making "X" amount of MPG. Cruising at the same speed at 6000', the air is thinner, so less drag which means more MPG.

I don't think it can get any more simple than that.

One thing I do know: At last years West Coast Bash in Montrose, I went 191 haul'n ass miles on 5.2 gallons of gas. :icon_eek: I don't think I could do that at 1000' elevation unless I kept it under 55 MPH.

In science you know you develop a theory and then test it. Keeping the other factors the same (this is the hard part), you change the altitude and measure the mpg.

BTW - In classical mechanics, work is not done on a body in a straight line at constant speed (body in motion stays in motion unless acted upon by a force). The distance they are talking about is a force applied at a distance like one pound at a distance of one foot (a foot pound of torque) not 37 miles down a level highway in a given time.

In our imperfect world, there is work done in overcoming friction (engine, chain, tires, etc.) and drag (small at 55mph to huge at 155mph). There is also inefficiencies in the engine especially at low throttle setting that sap mpg that may change at altitude even more than drag does. You may be able to calculate it all, but back to the original point, you would still have to measure it to see if you were correct so why not just measure and forget all the theories and calculations?

I stand corrected. It can get more simple. :icon_wall:

What we are trying to do here is fully understand why MPG is better. Thirst for knowledge, man!

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In science you know you develop a theory and then test it. Keeping the other factors the same (this is the hard part), you change the altitude and measure the mpg.

>>>yes

****

BTW - In classical mechanics, work is not done on a body in a straight line at constant speed (body in motion stays in motion unless acted upon by a force). The distance they are talking about is a force applied at a distance like one pound at a distance of one foot (a foot pound of torque) not 37 miles down a level highway in a given time.

>>>Bullshit; if I may be so rude. The work perfomed to overcome the aero drag IS a certain force for whatever distance we are talking about (37 miles or 37 feet, doesn't matter ) The force is variable, greater with higher speed as a rule of course.

You seem to be confusing torque ( a force ) which is often measured in foot-pounds, with work which is measured by force times distance, i.e pound-feet. Let me explain; imagine hanging a weight of 200 lbs from a socket wrench handle with a ten foot pipe attached, this will apply torque until something turns. The torque applied will be 2000 ft-lbs.If nothing turns then no work is done. Next consider dragging a sled behind you while walking for 100 feet. The force you must supply is equal to the friction force, lets say 20 pounds, and the distance you walk will determine how much energy you supply. So for a given distance the work is the same, i.e. 2000 foot pounds or pound feet. In the first case we appied a great force but performed no work. In the second case we definately performed work with a smallish force.

Now here is the interesting part. The rate at which you perform this work is what determines the horsepower. One horsepower is about 550 foot pounds per second, so performing the 100 ft sled pull in one second would require 2000lb-ft/(1sec * 550) or about 4 HP. And then you can see that doing the same thing in 4 seconds would require about 1 HP, i.e. 2000lb-ft/(4sec * 550)*******

In our imperfect world, there is work done in overcoming friction (engine, chain, tires, etc.) and drag (small at 55mph to huge at 155mph). There is also inefficiencies in the engine especially at low throttle setting that sap mpg that may change at altitude even more than drag does.

>>>>True! At low throttle pumping loss can be a major factor, feel how cold a throttle body/carb is at idle on most cars. This is energy lost cooling the intake air, it one major reason smaller engines get better mileage since they have the throttle open further and thus less expansion cooling.

****

You may be able to calculate it all, but back to the original point, you would still have to measure it to see if you were correct so why not just measure and forget all the theories and calculations?

>>>>Calculations and theories are fundamental to understanding and improving physical processes, Eric has shown great interest in these topics. While there has been some confusion along the way, it is people like him who wonder why and try to improve things that make this a better world.

If we were all content to just measure, then why not just buy what Consumer Reports says is best?

****

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Oh and here's a funny..... I'm lying in bed this morning, it's 2:30 am and I can't sleep, this mpg thing won't let my brain stop, so I lie there thinking, thinking I know the answer to this.... I know the answer to this.... I've done this all before, and I can't remember the answer, let alone explain it to any one else....

Then at about 3:30 am it hit's me....

There's a 20% increase in fuel economy because....................

........

(The next couple of sentences have been omitted from this post for suspense and intrigue, and due to the fact that some people, just aren't ready to know the answer, finding out the answer might kill there curiosity, and I wouldn't want to be the killer of curiosity....... at least not today anyways.)

........

Well I would have gone back to sleep.... except well, I had not told anyone yet....

Now I've told you, but now it's time to get up and start getting ready for work.

OK.... maybe I'll sleep better tonight..... that's after toDAY.... hehe...

Have a great day.

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"BTW - In classical mechanics, work is not done on a body in a straight line at constant speed (body in motion stays in motion unless acted upon by a force). The distance they are talking about is a force applied at a distance like one pound at a distance of one foot (a foot pound of torque) not 37 miles down a level highway in a given time.

>>>Bullshit; if I may be so rude. The work perfomed to overcome the aero drag IS a certain force for whatever distance we are talking about (37 miles or 37 feet, doesn't matter ) The force is variable, greater with higher speed as a rule of course.

You seem to be confusing torque ( a force ) which is often measured in foot-pounds, with work which is measured by force times distance, i.e pound-feet. Let me explain; imagine hanging a weight of 200 lbs from a socket wrench handle with a ten foot pipe attached, this will apply torque until something turns."

Why throw in "bullshit" if you misread what I was trying to explain asshole. I WAS explaining FORCE as in "acted upon by a force" and gave an example of 1 ft pound of torque (something we would all know). I was gearing up to explain work and power but thought better of it. You actually did a pretty good job.

BTW - I got almost 50mpg on a cold foggy night going across PA doing 70-80mph. The bike ran perrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrfect.

"Everything has been explained in this thread,nothing to add,if interested just read from the beginng ,,,,,,,"

Read it again just to be sure, all I got out of it is: Tampa likes soup a little thicker than Steamboat Springs.

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