Overdrive math re-visited

[Horst]

Well kids - I'm nervous. Not sure about what gas prices are going to do - but $4.00/gal is expected, and $5.00/gal is not out of the question in the not too distant future. Kind of makes my retirement traveling plans very difficult from a budget perspective.
So, time to re-evaluate the Gear Vendors over-drive unit.

If you have a Clipper (or any RV) that gets 8 mpg, you'll get 10 with a Gear Vendors unit. They cost about $4,500 (includes installation, taxes, shipping)

If gas costs $4.00/gal, you'll get your money back in about 45,000 miles.

Then there are the other benefits of the Gear Vendor units.....it's making me think again...............probably not gonna be RVing around as much as I'd hoped when I'm retired!

Lets hope gas prices stabilize (and drop some!!) soon - if they keep going up, it will stall any economic recovery, and make driving my Clipper very stressful!

[John Eversoll]

As in the news a few weeks ago they were already saying the gas

prices will be 5.00 a gal in 2012.  This gives us a year to enjoy the dcomforts of our Clippers..

Then it is either off  to the wrecking yard or just park the things till we can save enough for six weeks of gas travel....

What to do ------?

The govt will do what they want and we can not stop them

[JerryT]

Hi John

Have faith my friend! I think it will all work out in time.
I have a G.V. overdrive and I did not see a 2 mpg jump, more like .2 to .4 What is does is allow you to drive like a modern vehicle at posted speed limits with less rpms which I think is = to longer engine life. At 50 cents a mile, when you see the sign that the bla bla bla is 18 miles up the road it makes you think is it worth the extra $9 for me to see it? Or $18 if it is out of route. As the old saying goes you can't take it with you BUT it seems like it's getting harder just to keep it around while your here

JerryT

[Horst]

Jerry - you are only getting .2 to .4 better than before??
That is very sad to hear....makes me wonder.

I have only talked with two owners, one claimed 20% increase (mid 90s Chevy  truck towing an Airstream) and the other was an old-timer/full-timer in an early/mid70s Winnebago - a big Class A box - who says he went from  6mpg to 8mpg - and he drives all over the USA - and takes his time doing it. He likes to drive at night, and drives easy.
He said the biggest benefits next to the mileage gain was cabin noise and hill climbing. He had a detailed mileage log - and this was his third engine (440-3) - the first with the GV unit - which at that time had 6,000+ miles on it - not one problem.

So I went on the internet to check things out - and there are many people who claim significant mileage increases - BUT - there are also many who claim very little improvement (similar to your experience).

There was a trend though (rough science, small sample here) people with trucks tended to report significant gains, as did people with  older (carburated 3 speed) large Class A motorhomes. Many people with smaller class c motorhomes and newer motorhomes (fuel injected, 4 speeds, etc.) reported much smaller gains.

By the way - my pricing is wrong - it's about $4,000 installed.

Still - now I'm re-thinking my retirement set-up - maybe truck and lite travel trailer..........

[JerryT]

Hi Horst

I think your right on the money on the G.V. overdrive. I would never tell anybody that it was going to save them money---BUT--- I would tell them that it makes the rig more enjoyable to drive. There is nothing more enjoyable as having that second gear in overdrive mode for a passing gear. I keeps the motor in a nice RPM range. I talked to a G.V. Rep at an auto show about my application and he told me that the overdrive unit in 440 3 speed auto with 4.10 gears was a perfect match, and I think he was right. Mine was 2K+ and we did the install ourself, I might never see a pay back in fuel savings, I will see some pay back in extended engine life, and I got immediate pay back in drivability. I tell everybody I love the spunk and enjoy driving it and that I am less tired at the end of a long day, heat, noise, time. I still say that you can buy a nice Clipper, modernize it, and still have a large chunk of cash left over to buy fuel with, instead of buying a new(er) fiberglass 21'-24' rig as they are (new) 75K +++ and less livable too!

JerryT
   

[John Eversoll]

HI JErry or Horst,,,,,

I have a problem..

I justy droped the tank and found the sending unit to be

solid rust ...............

I have called Dodge and they No longer make the sending unit....


Where do I get  another one to replace this one.....?

I am sitting here with finger on the keys for a thank you......John

[Hank Jourdin]

Hello John, I changed sending units I both tanks, also changed fuel gauges to 12 volts> I used a universal sending unit on each tank. The 50 gallon tank was no problem, but the 35 gallon tank took a little doing.They cost about 40.00 each for the sending units, and I used 2 fuel gauges  at 50 or 60 bucks each. I have an electric fuel switch so when I change tanks a small led light which is right over the gauge lights up so you know which tank your running on. I got everything I needed at United Speedometer in Riverside. It was a lot of work but everthing works great!    Hank Out!

[John Eversoll]

Thanks Hank,!!!!!

I have wharis soaking with the toilet bowel cleaner right now --- But the sending unit is GONE....

I will call the guy up on Monday..

You are a big help......

JOHN

[USNRetired]

Fuel economy is about my only real complaint about my Clipper.  But I have adopted the attitude that while my RV gets pretty bad mileage for a vehicle, it sure gets great mileage for a cottage on wheels!!  The trade off being that I don't have to pay for motel/hotel costs, eat at a restaurant for the same reasons I go to the restaurant while at home --- 'cause I want to!  I can stop just about anywhere I want and fix lunch, hot cup of coffee or or or....  take a nap?  Can carry more changes of clothes than I could on the back of my motorcycle!  If I have to go to the bathroom sure don't have to look for a rest stop or convenient location with a big bush!  I could go on and on....  So I have to pay a little more for fuel... I think it's a pretty good trade off.  But I do need to consider either a larger fuel tank, 50 gal, or a second tank, maybe another 30 or so gallon tank.  I am also seriously considering a larger fresh water holding tank.  I already bought a portable 35 gallon gray/black water holding tank that I can pull to a dump station (very slowly of course).

[Horst]

Hey Jerry!
I re-read your post about only seeing a .2 to .4 mpg improvement.
What escaped was the fact that you said you're driving "modern" speeds.
Does that mean you're cruising along at 70mph???
Well then, I guess it doesn't surprise me that you're only seeing .2 to .4mpg improvement.
I wonder what you mileage would be getting at 55mph compared to before you installed the unit?
I'd bet it would be much better than .2 to .4 mpg.
I'm basing this on that old formula (can't find it just now) that they used to determine 55mph as the freeway speed limit back long ago - remember that?
It was something about wind resistance/drag starting to increase exponentially after 50 or so mph.
The increased energy required to push a box at 70 versus 55 is far greater than just the the 26% increase you'd see in a resistance free environment.

There's a really cool little mpg/travel time/cost calculator here
http://www.mpgforspeed.com/

but it's for cars - I'm sure the fuel efficiency degradation as speed increases for our Clippers are even more extreme.

Man, if gas goes to $6.00/gallon, I'm getting a gear vendors and driving 42mph - and I'll bet people will be slowing down on the freeways - I'm already noticing more people driving slower on freeways around here.

[JerryT]

Hi Horst

I think the slower speeds I am seeing people drive around here is from talk/text while driving
Yes I do drive 70+ when on the freeway, partly I like to run with traffic, and the bigger part is that my 440 seems to "notch in" around 73-75mph. I think that is where it makes it's best torque. I hope POP is reading this and can give his 2cents worth on the subject. When I am on the back roads (55) I do see a bit of mpg improvement (10%) but I get the mph creep if I don't watch it. If I drive 80+ (flat and no wind) I do see the mpg fall 10-20%, just like driving into a strong wind. The G.V. shifts into od at 40mph. We de-smogged the motor and put a Mopar quick advance kit in the distributor and set the timing to not ping on regular gas. This and my cooling mods make for a nice running/driving combo. Your right, if fuel costs continue on the path they have been on then travel will be constrained. I know that we have other energy choices---if allowed to come to market, maybe thats the silver lining in all of this. Check out these links.

  http://infogreenglobal.com/cella-hydrogen-based-synthetic-fuel-with-no-carbon-emissions/

  http://www.cellaenergy.com/

$1.50 gallon and works in present engines! Who knows what else is brewing in the labs around the world!!

JerryT

[Horst]

Unfortunately, most of the time, necessity is the mother of invention.
Greed and corruption often hinder invention for the common good.

[pop427]

I was going to stay out of this because it is a very complicated issue. First, there is no magic button but some things always stay the same. Aerodynamic drag increases at the square of the speed increase. Required horsepower increases at the cube of the speed increase. A motorhome being a big aerodynamic brick makes speed increase a important factor. So if it takes about 20 to 25 more HP to go from 60mph to 70mph.
Now the power comes from a variable speed device that does not get the same rate of efficiency at all speeds. So if your motor makes maximum torque at 3200rpm then that is the speed you will get the best mileage unless it is overcome by aerodynamic force increase. Remembering that the aero drag increase at the square of the speed increase really goes up fast. I tried to put the motorhome numbers into a very high dollar program and it would not even look at them. All I could get was error messages.

[pop427]

Sorry hit the wrong button.

The best way to test out the best mileage for your rig is to find a flat straight road and change speeds until you find the speed that the rig kind of floats along. Pay close attenation and you will see that in order to speed up you have to give it more gas than just a little. When I rebuilt motors for trucks or motorhomes I always asked what speed they wanted to drive because that made a difference what camshaft I used. Have your carb set so the secondaries don't come in until about 75% throttle. The primary circuit in the carb is metered much tighter than the secondaries.

If you can't cruise fast enough on the primaries then you need to richen up the primary circuit. Yes I said richen up. I made a lot of money and friends back in the phony Jimmy Carter energy crisis by making the primaries richer for the largest Winnebago dealer in the world. Then the coach would cruise on the primary and not keep getting into the secondaries.

Like I said at the start of this rant.   There is no magic button.      Doug

[Horst]

Funny you should describe it that way ("find the speed that the rig kind of floats along") - because I can feel that "sweet spot" in my Clipper - and it's about 52mph on my speedo, which I've tested against several other cars, and really almost 55mph. It does require a noticeable effort (gas pedal) to keep over 60mph (probably more like 63/64  actual mph), and I really have to get my foot into it to over 70mph.
I drove from Santa Cruz to SoCal (San Diego) and drove 70mph plus for much of the trip, and my mpg was UNDER 7.5mpg. This was with my old Holly two barrel set-up with stock intake, etc.
Many years later I made the same run. I drove under 55mph (drove late at night) and with my Edelbrock 4 barrel and Edelbrock intake and Flowmasters - and I got 10.4 - and that put a smile on my face. (That's still my record mpg for a long trip)
I think, just by the "feel" of it, that I'd get my best mpg at around 43-45 - but that's just a guess. And I would drive that fast on the freeway if I could - but I can't obviously. That's one of the reasons, back when we did take lots of trips, we traveled at night - cooler air, and I get to drive slower.