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Old 07-31-2002, 12:52 PM   #1
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The QUEST for 20-25 Miles Per Gallon

Hopefully, my auction buyer picked up a 5.9 liter, 1 Ton Dodge 3500 Van for me this morning. If not, he will eventually as that is his job.

I will be using this van daily for my job as a Realtor. I plan to keep it for at least 4 years and that will result in about 200,000 miles of real estate driving; and will include, at a guess, about 20,000 miles of trailering with my '72 Sovereign 31' AS.

I seek to achieve an average gas mileage of 25 mpg when not trailering and have done so in the past with a similar van; after all Dodge has been making this same van for about 35 years!!

I know that is possible, having done it. I seek 20 mpg when trailering and know that will be difficult; hence the quest.

My plans are to have ample cool air intake to a low restriction air filter; dual exhaust made of 4" eliptical pipes with double or triple cross-overs; tuned, large diameter, headers; a VERY HOT racing ignition system that will load many times the normal spark to the plugs; dual or multiple point plugs; tuned fuel system to run properly lean at normal highway speeds, even when trailering but have ample fuel available when I floor it for good acceleration; the very large radials will be suitable for 40 psi and mounted on wide rims, about 12" wide probably for more stability; sway bars will be largest available and HD shocks will be augmented by added spring capacity front and rear; rear of van will be set up to run, fully loaded, about 3 inches higher than back for better streamlining; I will run Slick-50 or some low friction lubricant in the engine.

I've probably forgotten several very important things. Also, and most importantly; I have not engaged upon a QUEST for power and mpg via vehicle modifications in nearly 20 years -- at least not to the maximum extent possible. Therefore I KNOW that there things available that I've never done before. Also; I've never had a forum or even one other individual to converse with or help me in my quest before.

Since there are many on here who have done all of the modifications that I plan, and then some; I hope to get guidance and input from you folks. I, most of all, need to find out what things are possible now, that were not possible or available 20 to 30 years ago, but are now.

I know the Tornado type swirling intakes are new and SEEM to be better than regular low-restriction, cool air intake systems. There are most likely other things as well.

NOTES: Eventually, I will need to rebuild or replace the engine; when I do that I will opt for some specialty items there. I will not change the differential ratio until I have settled on some larger wheels and some GREAT tires that will fit into the wheel wells and then I will change the differential to a limited slip with appropriate ratio to the tires and the job. The transmission will be the HD automatic with OD but I will not use the OD when trailering of course.

I seek all the input I can get from you folks who can walk the walk as well as talk the talk of increased vehicle efficiencies which result in more torque, horsepower and better fuel economy.

What have I missed, that I will need to further my QUEST.
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Old 07-31-2002, 02:18 PM   #2
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Gravity and Drag

Jody,
You have created quite a challenge for yourself.
I have a bone-stock, unmodified Ram 350 van, only changed the rimsand tires to a bigger, but still stock size with high load rating. I run 75lbs in the rear, 60lbs pressure in the front.
I get 6 to 10mpg towing my sub5000 lb trailer. I get an absolute maximum fuel mileage of 14.5mpg on the highway at about 70mph with teh cruise on in overdrive going flat as a pancake with no headwind.
I get 10 or 11 mpg around town. My van's engine and transmission are in tip top shape with fresh filters and good plugs etc. It takes some energy to move a vehicle weighing over 4000lbs empty. it takes even more energy to move the same thing with a huge twinkie hanging on it's bumper.
I encourage you to continue on your quest, but please don't be disappointed if your results don't quite meet your expectations.
I am sure one can make improvements to existing stats, but I am not sure we can beat gravity ( yet)!
Please share with us your individual results after you do mods to your vehicle.
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Old 07-31-2002, 03:52 PM   #3
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Hi Ewe,

As I mentioned above, I've done the 20 mpg with the same van in the past. I did all those things mentioned AND I usually carried about a thousand pounds of stuff in it, in addition to the van weight. I did not have the wide wheels but had wide tires on standard rims and I got a little over 20 mpg all the time, average, not just on good trips. However, the BEST I got was not much better. On a 100 mile trip on good roads at 60-65 mph the best I did was only a little over 22 mpg.

Gear ratio is important; that is overall ratio where the tire diameter is factored in as well. Your final ratio is probably, just a guess, about 4:1 which is great for towing and needed for hills, etc. My overall gear ratio on my old van was only about 3.3:1 which would REQUIRE me not using overdrive in hills and mountains due to the loads I carried; in fact when I went to hill country I carried more equipment and was probably up to about 1500 pounds or nearly so...

However, my current plan and I'm looking for more data, is to use the transmission in lower gears, not use overdrive at all, when trailering as well.

Do you or anyone else know if there is any reason to NOT use a lower gear for long distances in the Dodge 3500, 5.9 engine -- auto transmission? In the past, with the old van, and with a heavy payload, I was not putting as much constant strain on the engine and transmission as I will be doing when towing.

And, you are so very correct Ewe, I have set up a very high goal with the towing mpg I want. If I can't use the transmission in 3rd gear or even at times in 2nd gear for long miles, as compensation for the drive ratio, I'll really be in trouble getting the mpg I want. My plan is to have an overall drive ratio of about 3.4:1 again and use the gears to get down to the drive ratios closer to normal towing ratios of about 4 or even 5 to 1.

As I will not likely use my vehicle more than 10% for towing, I'm hoping I don't have to suffer the low gas mileage for the other 90% of my driving because I do drive so many miles. Any thoughts on damage I may do to the transmission by using it in 3rd or 2nd gear for long miles while towing??? I can't think of any, BUT, I don't know...
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Old 07-31-2002, 04:03 PM   #4
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No Way!

You can't break the laws of physics. With the van you mentioned, you MIGHT get 12 mpg towing a 31' Airstream. 10 mpg is more like it. You may get 20 mpg towing a 31 footer downhill.
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Old 07-31-2002, 04:32 PM   #5
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Hi Pick,

I won't be breaking any laws of physics. However I tend to USE them correctly, and as well as I can figure out, to get the better mileage. No physics laws were broken to take my old van from 10 mpg to 20 mpg either. I promise.
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Old 07-31-2002, 05:15 PM   #6
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MPG PHD

I do use ( have to) lower gears when going long uphill stretches while towing. My transmission specialist recommends using lower gears and keeping the transmission from constantly shifting back and forth to make it last longer. Heat and friction burn up a transmission. Keeping it from constantly shifting helps tremendously. It will burn up eventually, no doubt, but hopefully not while towing. I have it checked all the time, perhaps every 6000 miles, and the fluid and filter changed at that time. So far so good. This is the 3rd transmission in this vehicle. Two on Dodge, one on me ( 198000mls) Two burned up without ever having towed anything. ( Previous owner)
I take it out of overdrive when towing, 90% of the time. Only the occasional stretch of long downhills with wind in the back gets the overdrive. My rear end ratio is 3:93
My temp goes very high on long uphills, but not to overheating.
I have never never never seen any mileage better than 14.5 mpg with this injected 5.9 Dodge. It gets 10mpg towing a small 6x12 dual axle Uhaul trailer, and less with the airstream. Much less.
I got the 14.5 mpg after using Z-Max on a trip from Los Angeles to Nashville, going through the Texas Panhandle heading east, with no headwind. It was such an astonishing thing for this Dodge, I'll never forget......
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Old 07-31-2002, 05:49 PM   #7
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I had not heard of Z-Max before; but we got 10% better fuel economy on our airplanes when we went to Slick 50 from Dupont. I figured there are better and newer additives now than when we used the Slick-50 20 years ago.

You make some VERY good points about the Tranny and I'll remember them!!!
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Old 07-31-2002, 06:19 PM   #8
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I was quite interested to read your comments on Slick 50. I have a brother who is an industrial mechanics professor at a division of Penn State...and who did some studies on Slick 50 type products, and other teflon oil additives, and found no difference in engine wear with the products added. In other words they were mostly innefective. Now I am not saying that they did not improve your mileage, and if so would be worth adding for that alone.
I have seen a product used by dealers only for cleaning fuel systems that worked extremely well, and although i can't recall the name, it was supposedly similiar to Chevron Techron. Porsche actually recommends Techron, for what that is worth.

I put in the Tornado air manager, and did see an increase in power especially noticeable on take off, and also mileage. I estimate I went from near 7mpg to about 9.
The other factor here was I added new spark plugs (the old ones were not too bad, but it was time)...and did a good cleaning on the carb. Of course the 454 is never going to be a high mileage engine, and I crack up when I see ads for motorhomes like mine or bigger, that state they get 12-14 mpg. Isuzu diesels maybe.
Love your ideas guys!!
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Old 07-31-2002, 07:48 PM   #9
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454's

Last trip into PA, where it is quite hilly, I got 9.5 MPG (average) for the entire trip, pulling the Airstream. I was surprised that I got that, as I was expecting 8 or so.
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Old 07-31-2002, 10:05 PM   #10
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I did get some increased gas mileage in my Honda Accord and also in my Kawasaki motorcycle; about 10% in the Honda and less in the MC. However, since the difference was from 30 to 33 mpg in the Honda, the cost of the additive was not a good trade off for the mileage increase.

I have heard that the engine wear research by PA schools (the home of Pennsylvania Crude Oil) was not supportive of synthetic oils nor of teflon and molybdenum oils. Of course the claim by the synthetics and additives is that the deck was stacked in favor of PA crude oil products.

In our airplane business, before teflon, moly and synthetics, we used ONLY Pennsoil and PA crude oil products because they did have superior qualities. Since in the airplane business we had; we rebuilt the engines at least once a year, it was very important to reduce wear. Also since we ran the planes under very high stress for 10-15 hours a day every day in Agriculture Applications work, fuel consumption was substantial and the very high horsepower engines, working under maximum loads all the time use a LOT of fuel, so lowered fuel consumption was critical to expense management.

We sold the airplane business many years ago and the new owner may not be using any special oils or additives now, and may not be as meticulous of a record keeper. However, this discussion brings me to the point of calling him. I will ask him questions... However he is using only turbocharged and supercharged engines now, so his results may not be of critical importance to my purposes.

Hmmmm, now I'm thinking of a turbocharger!!! Of course that can not occur until I'm ready to rebuild an engine as I would want the engine set up differently if I were planning to charge it; with heavier bearings, harder pistons, higher compression, better rings, and a far stronger crankshaft... but still hmmmmmm... Turbo would give the big increases in torgue at midrange rpms...

That Tornado sounds impressive; that's OVER 20% increase by your reconning!
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Old 07-31-2002, 11:01 PM   #11
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Alan,
I agree with the Slick 50 statement. I had a German Car garage in SoCAl, and had many customers swear by it, and then swear at it when their cams in Mercedes V8's went flat, despite slick 50 and oil changes.
I have no clue why I tried this Zmax stuff, but it actually worked. It is not teflon. It has 3 or 4 bottles of additives for oil, atf and gas. Plus some sort of other stuff for small engines which I tossed in the dumpster. 5.9 is not a small engine....anyways, it was expensive, but effective. Not worth it in the long run, for fuel savings, because of it's high price. It made my engine noticably smoother and I actually got decent mileage after putting it in. It alsted about 2000mls, then everything was back to normal.
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Old 07-31-2002, 11:08 PM   #12
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EWE,

I had the same cost/effectiveness situations with the Slick-50. It wore out, it cost as much as I saved; so to heck with it... However, with the low mileage of my van; as opposed to the good mileage of my Honda; I was hoping that the cost would be justified for a more modern additive... it doesn't sound like it now.
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Old 07-31-2002, 11:17 PM   #13
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MPG

I used Chevron techron in a VW GTI I had every 3rd fill up and I can say it worked as advertised. Tried Slick 50, the only effect it had was I was $30 less in my wallet.
Today, to rebuild a 4 or 6 cylinder aircraft engine costs at least $15,000 if done in house and if all is within specs. I find it odd that you rebuilt every year, did the engines not hold up or did you fly that many hours?

John
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Old 08-01-2002, 12:26 AM   #14
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My suggestion

25 mpg in the ideal conditions you described in your motorhome post I see as possible with the empty van, but adding a trailer and expecting an average of 20 mpg would be an experimental undertaking. I applaud your efforts, but mileage engines and the torque engines needed to haul 12,000 pounds are diverse creatures. Gasoline has a finite energy per gallon, internal combustion engines are very inefficient. 25% of the energy from the gas is wasted as internal friction, 25% is converted to the rotary power of the engine and the other half goes out the exhaust as heat (hence turbochargers).

Your engine size is a penalty to begin with. You need a larger dispacement engine which can be run at a lower rpm and still produce the torque you need to move your van and trailer. The only you can get the power you need from this is to turbocharge and reclaim the waste heat in the exhaust, normally aspirated won't make it. To do this you need to convert the intake system to a pressurized system, seal and o-ring everything, create a new source of vacuum for the vacuum system. To get 20 mpg will require fuel injection and an electronic engine management system. This will have to be custom built because of the pressurization from the turbo. You will also have to construct the intake and exhaust manifolding, because I don't think you will find it as an off the shelf item at any parts manufacturers.

The machining on the internals of this engine will have to be extremely precise, the mains bored so perfectly and the journals polished so well that the crank will spin with a touch of your finger. This is expensive work and requires lead times of months to complete. All areas of friction must be reduced as much as possible, if there are two bearings they have to be align bored, roller chain on the cam, roller lifters, roller rockers, etc. The whole engine must be balanced, and assembled carefully to exact specs, checking all clearances and torques.

By using a turbocharger you can probably save the expense of porting, but the runners should be cleaned up, valve pockets opened up, and valves polished with a good multi angle valve job. Turbocharging will also save on the exhaust, you only need a single tube, unless you decide on dual turbos.

After this is assembled it really needs to be put on a dyno (chassis dyno would be best) and tuned for maximum torque. Horsepower is great, but torque is what is going to move the load. Big bucks, and you have just begun.

Turbocharged engines are hot engines, so you need to increase the cooling system capacity, plus devise a way to insulate the dog house and remove heat as quickly as possible, both for the sake of the engine and you. You will also need to plumb some fresh cool air to the intake system.

The transmission should be controlled by the same computer as the engine. If you took the inputs from the trottle position sensor, O2 sensor, speedo and tach it should be possible to write an algorithm to choose the best gear. Your plans to use the transmission in a lower gear will do nothing other than turn the engine faster (use more fuel) than a higher gear at a given speed. Stick with a computer control for the trans and torque convertor.

Tire height and rear axle ratio are a very important combination. You will need a 3.4:1 rear axle and the tallest tire you can fit in the wheel well. Engines that turn slower will use less fuel, have less friction loss. To get your target mileage you are going to have to keep this engine nice and slow- low gear, tall tires. Wide tires are the enemy of mileage; high pressure, yes but no wider than you need to support the load.

The aerodynamics of the package are incredibly poor, a box to break the air, a swirling suction area between the van and trailer, and a relatively streamline shape to follow. I say relatively, because the roof air, awnings, etc. destroy the smooth flow you will need. Aerodynamic work of this package might be nearly useless, it is hard to streamline a box, and I wouldn't loose the air and awning for an 1/8 mpg.

These are my general suggestions for your quest. It can be done, but not with Slick 50 and tornados. I wouldn't want to see the bill, and I sure wouldn't want to drive it.

John
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