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Step 2Improving aerodynamics
This is what I did on my 1983 F-250.
Not everything will be directly applicable to your vehicle. Modify and improvise as appropriate.
-I added an underbelly panel to smooth airflow beneath the vehicle made from Coroplast (corrugated plastic - the stuff cheap signs are made from). It is attached to the front bumper, and about 1/2 way back with cut outs for the wheels to turn, and a cut out for oil changes (and to avoid the hot exhaust manifold). Then there are smaller pieces anywhere a pocket of air could collect, while letting the transaxel and muffler plenty of space.
-I built some homemade wheel "skirts" (wheel-well covers) to improve aerodynamics. The current are made of cardboard coated in layers of aluminum tape, and then painted and edged with velcro. I lined the wheel well with velcro, and stuck 'em together, then taped over the seams with clear tape to cover the gaps of a less than perfect measuring and cutting job. These were originally just supposed to be a test, but they held up to a winter of rain and months of hauling, so I have no motivation to replace them.
-The headlights come in a little scoop. I had covers custom cut out of thin Lexan plastic, which is totally clear, scratch resistant, flexible, and nearly indestructible (the same stuff my custom motorcycle windshield is made from). I traced the headlights and brought the tracing to Tap plastics who were able to cut them for me in about 5 minutes. I drilled holes in the corners and screwed them onto the grill so I can easily remove them if a headlight burns out.
-I taped over the front turn signals, (because tape is cheaper than Lexan.)
-I removed the windshield wipers (inc. the entire arm). They come off in a few seconds with no tools. I keep them inside the cab, just in case I get caught in unexpected rain.
-I installed a tonneau cover which, in addition to increasing the trucks aerodynamics, will keep small loads clean, dry, and protected, making it a (semi)legitimate business expense.
I cut triangles out of plywood to mount the cover's rails at an angle, so that it tapers down from halfway up the window to the tailgate.
Having it angled this way makes it much more aerodynamic (I picked up about 1-2mpg just from tilting the cover), but having it go only 1/2 up the cab instead of joing at the top of the roof means I can still see over it and don't lose any visibility to the rear. It rolls up so I still have full access to the bed when I need it.
Not everything will be directly applicable to your vehicle. Modify and improvise as appropriate.
-I added an underbelly panel to smooth airflow beneath the vehicle made from Coroplast (corrugated plastic - the stuff cheap signs are made from). It is attached to the front bumper, and about 1/2 way back with cut outs for the wheels to turn, and a cut out for oil changes (and to avoid the hot exhaust manifold). Then there are smaller pieces anywhere a pocket of air could collect, while letting the transaxel and muffler plenty of space.
-I built some homemade wheel "skirts" (wheel-well covers) to improve aerodynamics. The current are made of cardboard coated in layers of aluminum tape, and then painted and edged with velcro. I lined the wheel well with velcro, and stuck 'em together, then taped over the seams with clear tape to cover the gaps of a less than perfect measuring and cutting job. These were originally just supposed to be a test, but they held up to a winter of rain and months of hauling, so I have no motivation to replace them.
-The headlights come in a little scoop. I had covers custom cut out of thin Lexan plastic, which is totally clear, scratch resistant, flexible, and nearly indestructible (the same stuff my custom motorcycle windshield is made from). I traced the headlights and brought the tracing to Tap plastics who were able to cut them for me in about 5 minutes. I drilled holes in the corners and screwed them onto the grill so I can easily remove them if a headlight burns out.
-I taped over the front turn signals, (because tape is cheaper than Lexan.)
-I removed the windshield wipers (inc. the entire arm). They come off in a few seconds with no tools. I keep them inside the cab, just in case I get caught in unexpected rain.
-I installed a tonneau cover which, in addition to increasing the trucks aerodynamics, will keep small loads clean, dry, and protected, making it a (semi)legitimate business expense.
I cut triangles out of plywood to mount the cover's rails at an angle, so that it tapers down from halfway up the window to the tailgate.
Having it angled this way makes it much more aerodynamic (I picked up about 1-2mpg just from tilting the cover), but having it go only 1/2 up the cab instead of joing at the top of the roof means I can still see over it and don't lose any visibility to the rear. It rolls up so I still have full access to the bed when I need it.
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Tailgate down - 24mpg.
Oh, Mythbusters has been caught outright lying about a great many things. And intentionally skewed results from a lot of other things as well.
Great entertainment, but please do not believe anything they say. They do it for entertainment value only.
BTW, how come no one has done an experiment with the tailgate removed?
And another one with those cargo straps for a tailgate?
2003 Chevy S10.
I have an iPhone App that reports real time MPG via the OBD2 port.
No tailgate, 29.8 mpg!
With tailgate, 30.3 MPG!
With hard Fiberglass Bed Cap 30.7 MPG!
With thin Plastic vehicle specific,'Cab-hi Shell, 30.6 MPG.
With the tailgate and the Shell Hatch removed, 30.8 MPG.
With a round tail-cone installed and sealed to the rear of the bed and shell, lots of duct tape!, 31.2 MPG.
These tests were made at the same time, during the same commute, down the same highway and reflect the average collected during a FULL WEEK of commuting for every result!
The Saturday before each of these weeks, the battery was disconnected, overnight, to reset the computer in the truck. This way the computer relearned the trip for that week. The ONLY modifications made were to the rear of the truck.
I have not yet tackled the front of the truck! I could change the grille, the head lights, use clear tape to seal any 'dirty' gaps. remove the windshield wipers. I could really go nuts with this stuff! But the truck has the 4.3 V6 and Over-drive Automatic. I KNOW I am doing damned good with the MPGs I am getting!
Do you believe dinosaurs didn't exist too?
But Mythbusters is strictly an entertainment show, nothing more.
Fun to watch them blow up stuff.
And no, I am not the paranoid type. I am more of a doubting thomas of sorts.
If I cannot recreate their experiments with the same or very similar results, then their show is a farce.
There have been complaints with them about some of the things they show.
Maybe googling 'mythbuster lies' could be of use?
Sure, it is primarily entertainment. And they don't always follow scientific procedure when it isn't convenient.
But they do deserve credit for bringing the concept of "don't take someone's word for it, actually try it" to a more mainstream audience.
As a "doubting Thomas" myself, I appreciate them for that.
How many miles did you do for each one, and under what conditions?
What method did you use to measure mileage?
So they really only proved it for that specific truck.
There have been other people to test and get different results. They just didn't have a popular TV show!
Anyway, what I have now is more aerodynamic than tailgate up, down, or flat tonneau, making the issue moot.
As to airconditioning, you get the best efficiency of all by having the A/C off AND the windows up. Put a beaded seat cover over white seat covers, tint the windows, paint the roof metallic silver, take off any excess clothing, and open the vents.
Cold air is denser than warm air, therefor you get more oxygen molecules in the engine at once, therefor you can add more fuel and maintain the proper fuel/air ratio, therefor you can generate more power.
This is also the principal a turbo charger runs on (compressed air is also denser)
However, more power does not always translate to better efficiency.
There is significant debate among serious hypermilers as to whether cold or warm air intakes produce better mileage.
Either way, having a cold engine has nothing to do with the air intake temperate (which normally does not come from the engine compartment)
A cold engine is less efficient.
This is why diesels have glow plugs, cars is cold climates have block heaters, people used to "warm up" old carbureted engines, you avoid taking a car to get smogged without driving it a while, and they recommend combining several small trips in a row rather than spacing them out.
I appreciate your interest, but that was crazy long!!!
At least some line breaks would have been nice.
Anyway, the majority of what you say is accurate, but I didn't see need to go into that much detail or explanation.
The bottom line on engine temp is, all other things being equal, a cold engine (measured by coolant temp) runs poorly and gets less MPG. In a diesel it will even stall. It needs a certain minimum temperature to support complete combustion. On a cold day, this temperature is reached (and maintained) easier with the grill block.
As to power efficiency not always equaling fuel efficiency, I wasn't referring to unburned fuel, but rather to drawing less fuel into the engine (using less throttle).
It came up in regards to a question about rate of acceleration.
My point was that, even if you get better power to fuel ratio at full throttle, if you don't need to go that fast, you are still wasting fuel.
Consider this analogy:
The store has a sale - you can buy one refrigerator for $100, or you can buy 2 for only $150. Buying two is more cost effective per unit (only $75 each). However, you are spending more overall; if you don't actually need 2 refrigerators, you are wasting that extra $50. In this case, the less efficient-per-unit deal is actually the more efficient overall.
In the same way, going from one stop light to the next a block away at 3/4 throttle is a waste of fuel, no matter what the BSFC map says. This is why I recommend acceleration gently in city driving.
I think all of your last tips are all valid, but I am trying to stick with things which are inexpensive and don't require much technical knowledge of engines.
Cold air = HP. That much is known. And in some circumstances, HP can increase fuel economy. In other circumstances warm air provides better fuel economy.
In fact, among the hard-core "vehicle modifications to increase fuel economy" crowd there is a long on-going debate as to whether deliberately warming intake air helps or hurts mileage.
Anyway, I am not advocating warming the intake air. In most vehicles the air isn't drawn directly from under the hood anyway. While a warm engine will warm the air passing into it to some degree, there is still a difference between a warm engine and warm air intake.
My original statement was just that a cold engine runs poorly and inefficiently.
Cooling systems are designed to keep the engine from overheating on hot days under full load, and since 99% of the time those conditions aren't both true at once, it can be advantageous to take steps to warm the engine sooner and keep it hotter.
If I drop to 60, I get around 24, and if I get up to 75,80mp it drops to 22.
Whats up with that? Does it have to do with the computer chip?
While it is true that driving faster than the rate a vehicle was geared to be most efficient at will reduce MPG, driving slower does not always improve MPG because vehicles are designed to run at certain speeds. The vehicle described in this Instructable is a 1983 model, and was probably designed to be more efficient at 50 mph rather than 60 or 65.
It only has a 3 speed (plus an extra low, which is rarely used) transmission, no overdrive.
However, regardless of gearing, there is an upper limit to efficient speed imposed by aerodynamic forces which increase exponentially with speed above around 40MPH or so.
This effect will be larger the less aerodynamic the vehicle is (and the Sportage is a box shaped SUV)
Both of these factors interact to give an optimal speed for each vehicle, but it is usually in the 40-60MPH range
Usually it is the speed you are going exactly after transmission shifts to highest gear. Since I have no overdrive, thats at 25mph. If I hold it at 25 exactly, it lugs just a little.
With a high enough overdrive, and an un-aero-dynamic enough shape, it could be lower than that, and if a vehicle is especially air-resistance-friendly it might hypothetically be a little higher depending on the power curve of the particular engine.
w/o buying the proper instruments, you can figure it out roughly just by driving slightly faster every day for a whole tank of gas and recording mileage, (miles driven since last fill up divided by gallons added), and then drive slightly slower every day for the next tank. Be totally consistent, use cruise control, and see which gets you better mileage.
On a second trip of same length I went 75... this then went down to 22 again.
I also was not aware of wind direction on any of the trips, I also hyper miled on some and tagged behind semis which worked slightly... but I don't think is actually worth the risk.
I was able to cruise at 65 mph IN my 94 XFI metro WITH a trailer massing over 500 pounds and still score 55mpg by drafting semi's
its NOT risky unless your a nimrod. That semi CAN NOT out brake you.
I don't care HOW hard he slams on his brakes I don't care WHAT he hits. Your brakes won't even have to work hard to "out brake" a semi.
its simply physics simple inertia.
as long as your back far enough to account for "reaction time lag" and a little more for safety you are perfectly safe.
What if you fall asleep? the issue their was you falling asleep not your distance to the semi.
I will tail a semi at 45-50feet without hesitation. If I have the CB and "get the ok" from the driver I will cut that to 30ft and get some SERIOUS FE improvements (and dramatically reduced noise since I am in his suck zone)
I get behind a semi so he can see me and call out to him. Hey mr trucker in the estes semi. I the little blue mouse behind you.
You mind if I snug up behind you while you punch some atmo for me.?
They get a chuckle and almost always say "have at it little mouse"
The only reason I stopped using semi-drafting is because around here they tend to drive 65mph (technically illegal for them, but not enforced) and, with my lack of overdrive, I try not to go above 55.
Not only does a car have vastly superior braking power, but semi drivers tend to be very steady and predictable, making it very different to follow them than a random car driver.
I like the CB idea. I've heard of some truckers objecting to being tailed (which is odd, since it actually improves their mileage too) but asking first would probably make a huge difference
as for truckers. I understand. suddenly someone it right on your butt and you have no idea why. You can't see them You don't know what they are doing or why. Yeah I can see how that would freak them a little bit.
so anytime I want to get close enough that they can not "see" me in the mirrors anymore I always ask permission.
You already mentioned the two biggest variables: wind direction and elevation.
You can compensate for elevation, and more or less for wind, by doing the same trip at the same speed in both directions. Out and back at one constant speed (use cruise if you have it). That way, any uphill you do one way cancels out going home.
Then do the exact same trip again, same start point, same end point, same route, at a different speed, there and back.
Even a slight grade or headwind, one you would never notice just by looking at it, could easily explain 1 or 2 mpg.
Of course it may not be practical to take two 3 hour road trips back to back (and it has to be close together, because overall weather conditions affect mileage too; you will get noticeably better or worse mpg in winter vs summer)
So an alternative is to just make sure all of your highway driving is at a constant speed, where ever you go, for a full tank of gas. Over the course of a full tank your uphills and downhills, headwinds and tailwinds, should more or less balance out. On the next tank do all your highway driving at a different speed.
That seems unlikely, as all but the most aerodynamically shaped vehicles (as in experimental cars; nothing you can buy from a dealer) suffer from increasing wind resistance above around 40-50mph.
On the other hand, higher gears result in better mileage. If a car has a higher overdrive gear ratio than average, that would tend to push optimal speed up a little higher.
There could also be other factors: traffic patterns, intersections, hills, that could come into play that you haven't been aware of. The only way to really be sure is to drive the exact same course several times with the cruise control set at a particular speed, multiple times each, at least a hundred or more miles in each direction and calculate the average mileage for the trip at each speed.
on the outside it blocks the entire grill and the fins and all, making it all perfectly smooth