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11Instructables883,563Views257CommentsOakland CA
I am an ordinary guy. Except that I live in an RV, drive a 250cc motorcycle, have a truck that runs on bio-diesel, am vegetarian, and have had almost 30 jobs in 10 years, including armored truck driver, bicycle messenger, medical test subject, TV commercial actor, "adult" actor, ditch digger, lab assistant, liquor store cashier, secretary, non-profit fundraiser and carnie. Now I am running my own small business, which is the only one of its kind which has been certified green in the …

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  • Vehicle Efficiency Upgrades: 30+ MPG in 2.5ton Commercial Truck

    I'm afraid I've got bad news for you. You are never going to make an RV fuel efficient. There's just too much working against it. The shape could not be worse for aerodynamics. It's heavy. It's motor is huge. They aren't designed with efficiency as a priority.About the best thing going for them is that people aren't surprised when you are driving slower than normal.Don't get me wrong, I'm a fan of Rvs. I lived in one for most of my adult life, from around 19 until 33. I've owned 3, drove one clear across the country and back. My big orange truck was originally purchased to tow an RV trailer. I credit RV living with being nearly financially independent after a lifetime of living at less than half the national average income.But you can't argue with physics. There are things you …

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    I'm afraid I've got bad news for you. You are never going to make an RV fuel efficient. There's just too much working against it. The shape could not be worse for aerodynamics. It's heavy. It's motor is huge. They aren't designed with efficiency as a priority.About the best thing going for them is that people aren't surprised when you are driving slower than normal.Don't get me wrong, I'm a fan of Rvs. I lived in one for most of my adult life, from around 19 until 33. I've owned 3, drove one clear across the country and back. My big orange truck was originally purchased to tow an RV trailer. I credit RV living with being nearly financially independent after a lifetime of living at less than half the national average income.But you can't argue with physics. There are things you can do that will help, absolutely, but don't expect miracles.The airflow bullet truck managed to get 13.4 mpg average hauling freight coast to coast, after 3 years of research and development (and 30 years of experience) for a truck built specifically for maximizing mileage. Thats a huge improvement from the standard 6mpg for a semitruck, but 13.4 is still pretty dang low.That said, better is always better than not better, and if you have to drive, may as well use as little fuel as you can.Start with speed. In something as unaerodynamic as an RV, speed will have much more of an effect on you than it does on a car. When I crossed the country, it was at about 50mph. It takes a little longer.To the extent possible, keep it areodynamic. If you have a long trip, consider removing stuff that sticks out, like roof racks, rolled up awnings, TV antenna, etc. Wheel well covers and underbody panels.I would advise against paralleling your house and engine start batteries, because then you can't use the house battery to jump start your engine if they both die together. But there is no reason you can't replace your start battery with a deepcycle, which will help it last longer between charges. However, its only advisable to disable the alternator if you have a diesel engine, because you may get a weak spark from the 12v a battery puts out, vs the 14v from an alternator. How much that will matter depends on your specific engine, so you could always experiment with it. Some people on the ecomodder.com forums have tried boosting the battery to 14v with a converter, and some just run gas engines at 12v. you may want to register and post on that forum for better tips, they are all enthusiasts of maximizing fuel.Since an RV has such a wide flat roof, and uses a lot of power, and already has battery storage and has all 12v lights and appliances, it is perfect for solar, which could potentially charge house and engine batteries if you do go that route.Best of luck, and send me an update if you do start tinkering with it!

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  • Yup, I've read that a number of places. I even tried modeling a simulated air tunnel myself, when I was deciding on how to build my cover:

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  • 1) This is really old! I don't even own the truck anymore...2) I actually did try a "boattail" fairing at once point, but my mileage actually went down slightly. No windtunnel for proper design and testing :(3) True, higher pressure can lead to more easily damaged tires from potholes and nails and such, and could possibly shorten life. But (outside of snow, mud, sand, etc) it should provide similar traction (on smooth roads) and actually better handling. The main sacrifice with higher pressure is ride quality (i.e. you feel more road vibrations - on a very bumpy road at high speeds it can decrease traction just because it bounces slightly over bumps). Besides, I did regularly carry maximum loads!4) I am unfamiliar with the chalk test, care to elaborate?

    The boattail experiment:

    I loved the truck, but I was doing mostly handyman work and very little hauling and moving, plus a baby on the way - no safe way to put a child seat in the truck. My new Jetta wagon has enough room for all my tools (and ladder, and materials), but can convert to a family friendly mode - it gets better mileage at its worst than the truck at its best; AND it still runs on biodiesel.As far as tire pressure, I don't claim to personally be an expert. But I can provide links to people who do:"If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steer…

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    I loved the truck, but I was doing mostly handyman work and very little hauling and moving, plus a baby on the way - no safe way to put a child seat in the truck. My new Jetta wagon has enough room for all my tools (and ladder, and materials), but can convert to a family friendly mode - it gets better mileage at its worst than the truck at its best; AND it still runs on biodiesel.As far as tire pressure, I don't claim to personally be an expert. But I can provide links to people who do:"If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point."https://www.tirerack.com/tires/tiretech/techpage.j..."One tire expert from the Edmunds.com testing team said that this slightly compromises braking distances but actually improves handling because it provides more "bite" as the tire flexes during sharp cornering. This expert said he chooses 4 psi over the specified level."https://www.edmunds.com/fuel-economy/edmunds-emplo..." the vehicle manufacturers specifications are either patently too low (for this area), or barely adequate."https://www.souzastireservice.com/tires-101/air-pr...However, almost no one ever specifies exactly what "overinflation" refers to exactly. Overinflated by more than the tire max is likely too much - although one company *doubled* max sidewall pressure and failed to find the limit of improvement (in wet conditions): "Michelin performed a hydro­planing resistance test using pressures above the “max press­ure/max load” rating. The test was motivated by the common practice among law enforcement officers of inflating their tires above that recommended by the vehicle manufacturer. The test almost doubled the “max pressure” without discovering where hydroplaning resistance reached a plateau."https://www.tirereview.com/can-psi-adjustments-fix...From the same site "Can we improve handling and ultimate grip by increasing tire pressure? You bet! I participated in several at-the-limit, race-track-style pressure tests. We found that increasing the pressure on the end with less grip worked wonders. " The car manufacture sets the recommended pressure with ride comfort as a significant factor:"Engineers determine how much pressure we require to support the vehicle and its load. With passenger vehicles they also consider ride comfort. With less air pressure the vehicle rides more comfortably. Less pressure allows the tire sidewall to flex, which absorbs roughness in the road. This flexing also damages the tire and promotes faster wear.This is why on passenger cars, the tire placard rating might be considered the minimum.Some tires experience excessive wear with the vehicle manufacturer’s recommended pressure. In such cases, they may base the recommendation too heavily on ride considerations. As tire pressure increases, ride comfort generally decreases. This is because we reduce tire flexing. More pressure may also increase tire life and fuel mileage, up to a point."http://www.agcoauto.com/content/news/p2_articleid/...The chalk idea makes a lot of sense, except it seems it would be most useful if done in real world conditions - i.e. with the tires at the average temperature they are at when in use, and at the average speed they are driven at.

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  • interesting theory. I suppose humans did not live in countries with hot weather before the early 1900s, when A/C was invented? That's funny, because I'm pretty sure people actually did live near the equator before 1900. Which would imply it actually is physically possible. Perhaps what you meant was that in the country you live in car windows can not be rolled down? This is equally surprising, but I haven't lived everywhere, so I grant that it is possible.

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