Improved MPG into headwinds

[Fiesta48]

On the other "big RV" website I did a posting on my Ram Air and the head winds we encountered over labor day. Of course I got the usual "that can't work" Based on upon the facts I recorded it does. This has occured over several other trips.
I installed a plastic dryer ($10) vent upside down, flapper removed, 10" behind an open area of the grill with a water drain hole for rain on the air intake. The OEM intake tube (2" smaller in dia. than the balance of the system) was behind a large rain deflector shield. It had to be a low air pressure area.
And most people say a K&N style air filter is "Bad" for your vehicle. I've been using them on about 20 vehicles for hundreds of thousands of miles with no bad results. And no dust upstream. My F53 has one. I always get 1-3 more MPG with one.
Well, we got 8.8 MPG when we normally get 9.0, going into a 20-25 mph headwind last weekend on a 300 mile trip. (Flags straight out and several websites confirmed wind speed) Scan Gauge and fill up confirmed the same. Ram Air works.

[awarnes]

OK. I still don't believe your results. Its simple physics. You have a big broad face vehicle moving forward at a certain speed into a wind. Go read Newton's 3 Laws of Physics. What you state is scientificly impossible. Force and friction come into play on this one buckoroo.

Arnold

[DBOL]

Quote:

Originally Posted by awarnes OK. I still don't believe your results. Its simple physics. You have a big broad face vehicle moving forward at a certain speed into a wind. Go read Newton's 3 Laws of Physics. What you state is scientificly impossible. Force and friction come into play on this one buckoroo. Arnold

Did you come from the other Big sight to call someone a Lyer if so go back!

[Camping4fun]

It never hurts to day dream.

[ga traveler]

Quote:

Originally Posted by awarnes OK. I still don't believe your results. Its simple physics. You have a big broad face vehicle moving forward at a certain speed into a wind. Go read Newton's 3 Laws of Physics. What you state is scientificly impossible. Force and friction come into play on this one buckoroo. Arnold

I retired from Delta Air Lines. For twelve years I built Jet engines. We continually modified them to get better fuel consumption. the airplanes stayed the same. Same drag coefficient etc. Yet we improved the fuel mileage.

[njs42]

I do not understand exactly what is being said----we got 8.8 MPG when we normally get 9.0---sounds backward to me. Maybe I am reading the results incorrectly?

I get the Ram Air idea and I'll take your word that you experienced improvement.

MPG is effected by many other factors, tire pressure, sustained speed, speed variables, weight, head wind speed and actual direction of the wind, road condition, how consumption was measured (Scanguage evidently) etc; Any change of the above from one test to the other can alter the results.

You seem quite satisfied with your results so congratulations.

[TN Bill]

Please show me some pictures I am a little confused as to what you did but would be interested in trying the same thing. Anything that would increase MPG and not cost a lot I would try.

[wa8yxm]

There is a way to improve MPG in a headwind... WAX THE RIG!

Works w/o a headwind too. I do mine over the next two weeks.

[njs42]

Quote:

Originally Posted by wa8yxm There is a way to improve MPG in a headwind... WAX THE RIG! Works w/o a headwind too. I do mine over the next two weeks.

Mine gets waxed twice per year sometimes and once per year every year----the trouble I have it gets dirty when I drive it particulaly after slogging through five days of winter weather.

But it is as slick as it is going to get (roof too) and I have no doubt it helps at least a little and if it were not waxed the grime would cling all the more.
Generally speaking routine maintenence is a huge contributing factor in mileage; tune up, tires, oil, etc; it all helps.

A thousand miles of flat fresh rolled asphalt and a tail wind-------be with you all.

[Perry White]

only headwind MPG increase is when I follow a big rig about 100 ft back.

[Kathy_MD]

Mr. Fiesta stated he increased his MPG by .2 according to his Scangauge. Well, if that was what the gauge stated then that is what it is and I believe him. I have that same gauge and believe it accurate.

Now, attributing that increase to his Ram Air modification...this is where I believe other factors are at work.

Simply put, the advantages of ram air at our highway speeds (anything below 150mph) is almost immeasurable.

Let's define so things first:

Static Pressure: This is the pressure we all live with. 14.7 lbs/sq in at sea level. It lowers the higher in altitude we go (which is how an altimeter works by the way). It is also in our tires - static pressure of maybe 80 psi.

Dynamic Pressure: This is the pressure (force) we have all felt when we stick our hand out our RVs window. It is the pressure that is caused by forcing the air molecules around our hand.

Engines - gas, diesel, jet fuel (JP) all require STATIC pressure to operate, and for gas engines, the fuel is mixed with the incoming air at a ratio of 14.7 to 1 (you E types will recall this as the stoichiometric ratio).

Now, this is the important part. At speeds below about 150mph or so, you cannot trade dynamic pressure for static pressure. I underlined this because it is a fact. (You E types see the fluid dynamics behind this).

Proof of point....

Find the largest funnel you can find. Attach a hose to the end. Attach the other end to a child's balloon inside the RV. Stick the funnel out the window at 70mph or, as fast as you care to drive your RV (feel the Dynamic pressure). Think it will blow up the balloon? If you answered no you are correct. And, a child's balloon only requires about .25psi (static pressure) to inflate. (A healthy human can create about 2psi).

Ok..now that the ram effect is, for me, ruled out as a possible cause for increased MPG, lets look at other logical factors - altitude, temperature and fuel source.

Recall that at lower elevations air pressure is higher (static - see above). Also recall that lower temperatures air is denser - engines like dense air. It weighs more than warm air and fits into the stoichiometric ratio (see above).

My point is that variance in MPG could be cause by simply driving in colder air, a low pressure area (the big "L"s on a weather map, or a lower altitude.

I might have considered COI (or Cold Air Induction), meaning that the air intake source is moved from the engine compartment to somewhere outside to get colder (denser) air, but since this is a F53 and the air intake is in front of the radiator, it is a moot point.

Air density variations caused by altitude, humidity, temperature could also change the drag felt on your RV. You E types will recall that the "p" in the drag equation is the mass density of the fluid (or air in this case) and is a major factor. Driving our RVs at higher altitude decreases the drag. It is also why planes fly high (and there are more reasons but for simplicity..) because of less drag. Since I am talking about drag here, our RVs have a Drag Coefficient close to 1. A typical Saturn is about .3. If you drive at 55 and then change to 70, you have increased your overall drag almost 4 times. Quick formula, drag increase = square of speed increase. It pays to drive slower when you are driving something with the aerodynamics of a brick (a brick's drag coefficient is 1.05).

Another factor is fuel. Just because it states 97 or 83 or whatever, does not mean you wil get the same MPG from every supplier. There are variations - especially from season to season. You can google this elsewhere for more info.

So, After typing all that, I DO believe that Mr. Fiesta experienced an MPG increase. Do I believe his increase was due to his his innovative engineering...no. If I, and the numerous RV manufactures and Truck manufactures, thought that ram air was viable, I would have installed in my RV yesterday. And most likely your RV or Truck would come standard with ram air.

[Midniteoyl]

Quote:

Originally Posted by Kathy_MD Mr. Fiesta stated he increased his MPG by .2 according to his Scangauge. Well, if that was what the gauge stated then that is what it is and I believe him. I have that same gauge and believe it accurate. Now, attributing that increase to his Ram Air modification...this is where I believe other factors are at work. Simply put, the advantages of ram air at our highway speeds (anything below 150mph) is almost immeasurable. Let's define so things first: Static Pressure: This is the pressure we all live with. 14.7 lbs/sq in at sea level. It lowers the higher in altitude we go (which is how an altimeter works by the way). It is also in our tires - static pressure of maybe 80 psi. Dynamic Pressure: This is the pressure (force) we have all felt when we stick our hand out our RVs window. It is the pressure that is caused by forcing the air molecules around our hand. Engines - gas, diesel, jet fuel (JP) all require STATIC pressure to operate, and for gas engines, the fuel is mixed with the incoming air at a ratio of 14.7 to 1 (you E types will recall this as the stoichiometric ratio). Now, this is the important part. At speeds below about 150mph or so, you cannot trade dynamic pressure for static pressure. I underlined this because it is a fact. (You E types see the fluid dynamics behind this). Proof of point.... Find the largest funnel you can find. Attach a hose to the end. Attach the other end to a child's balloon inside the RV. Stick the funnel out the window at 70mph or, as fast as you care to drive your RV (feel the Dynamic pressure). Think it will blow up the balloon? If you answered no you are correct. And, a child's balloon only requires about .25psi (static pressure) to inflate. (A healthy human can create about 2psi). Ok..now that the ram effect is, for me, ruled out as a possible cause for increased MPG, lets look at other logical factors - altitude, temperature and fuel source. Recall that at lower elevations air pressure is higher (static - see above). Also recall that lower temperatures air is denser - engines like dense air. It weighs more than warm air and fits into the stoichiometric ratio (see above). My point is that variance in MPG could be cause by simply driving in colder air, a low pressure area (the big "L"s on a weather map, or a lower altitude. I might have considered COI (or Cold Air Induction), meaning that the air intake source is moved from the engine compartment to somewhere outside to get colder (denser) air, but since this is a F53 and the air intake is in front of the radiator, it is a moot point. Air density variations caused by altitude, humidity, temperature could also change the drag felt on your RV. You E types will recall that the "p" in the drag equation is the mass density of the fluid (or air in this case) and is a major factor. Driving our RVs at higher altitude decreases the drag. It is also why planes fly high (and there are more reasons but for simplicity..) because of less drag. Another factor is fuel. Just because it states 97 or 83 or whatever, does not mean you wil get the same MPG from every supplier. There are variations - especially from season to season. You can google this elsewhere for more info. So, After typing all that, I DO believe that Mr. Fiesta experienced an MPG increase. Do I believe his increase was due to his his innovative engineering...no. If I, and the numerous RV manufactures and Truck manufactures, thought that ram air was viable, I would have installed in my RV yesterday. And most likely your RV or Truck would come standard with ram air.

x2

[Billieg]

Geesh.... I guess she told us! I'm not an E-type but it all made sense to me. Thanks for the explanation.

So, I guess the bottom line is: if he placed the intake outside of the RV like in the grill he would get denser air which may help the mpg?

[tomwalt]

I say DIY experimenting is a good way to learn - go for it and thanks for sharing your thoughts/results with others.
P.S. I must have missed the part where you were asking for someone to critique your results.