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Fuel economy ideas for an old RV

DRTDEVL

DRTDEVL

Mothfukle
Joined
May 19, 2020
Member Number
78
Messages
768
Loc
Austin... TX? Nope. Minnesota!
So I rock a 1980 Winnebago Minnie Winnie 20RG for a camper/hauler. Its the shortest RV you can find on a cutaway chassis of the era (20'6"), yet still has one of the last 440s tossed in an RV. Yeah, I know, almost zero compression from the factory (something like 7.95:1), so I'm never going to see real power out of it, but that's not what this is about.

So, anyway, it gets about 7.5 mpg when not towing anything and going only 60. That drops to about 5.5 mpg with my 7x16 enclosed and a pair of Harleys in it. With Sturgis around the corner, its time to consider what I am going to do to it this year before the trip.

First mod on the table: FiTech EFI kit. $1400 all-in, but will probably do wonders for cleaner exhaust and a more economical burn than the 800 cfm ThermoQuad that came from the factory. Anyone think this would pick up that towing mpg above 6.5 or 7?



Next up (probably for next year): Replace 727 with a built 47RH and a vacuum switch kit for an automatic locking convertor. This will get the RPM out of the stratosphere when going 60, and probably allow for 65-70 mph comfortably.

OR

Pay out the nose for a gear vendors OD. The cost is a little more than my idea of the 47RH swap, but the simplicity is there. How well have 727s with non-locking converters held up with a GV, and how well have the GV units held up when constantly loaded down in an RV towing?

TL;DR: Will EFI help my fuel economy enough to justify the price? Will a built 47RH be better than a Gear Vendors OD?
 
Fuck anything that's made by FiTech. That is all.

Oh, and forget the GV unit, they won't hold under the weight of your RV.
 
They will absolutely hold under that piss ant rv. Ive put them in way bigger.

Id tell you not to because they are more exspencive than a o/d trans and you WILL NOT see any mpg and will more than likely just bog down and be out of it most of the time. Youll only get shift at 2nd and 3rd gear
 
total newb said:
They will absolutely hold under that piss ant rv. Ive put them in way bigger.

Id tell you not to because they are more exspencive than a o/d trans and you WILL NOT see any mpg and will more than likely just bog down and be out of it most of the time. Youll only get shift at 2nd and 3rd gear
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Indeed, it is tiny for the chassis size (MB400, 1 1/4 ton class 4)

RV Trailer.jpg



As for the power? I've been doing some reading, and it would seem that I can gain quite a bit by remapping the timing to 12* initial and 38* total with a weight kit. Some have suggested the Comp 268/280- Xtreme Energy cam as an option, but that seems more street-rod driven than off-the line torque. I figure with the cleaner burn of EFI and more timing, I should be able to pull a little better and gain about 20% fuel economy.
 
I joke, slightly, with the “LS swap.”

but with 7.x compression, non-lockup 3-speed... you’re probably money ahead with a pull out 6.0/6l80 than throwing thousands at your current setup
 
rockota said:
I joke, slightly, with the “LS swap.”

but with 7.x compression, non-lockup 3-speed... you’re probably money ahead with a pull out 6.0/6l80 than throwing thousands at your current setup
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Indeed I would. If the 8.1 fit in there nicely, it would be an option, but the rails are too narrow for an easy swap.

I have even considered getting a wrecked 94-95 Ram 3500 2x4 Cummins for a donor truck and swapped the entire front end under it, along with the entire drivetrain (axle, too), but then we're looking at a MONSTER doghouse. Perhaps better off thinking 6.2/6L80e(?). In the end, this RV was my grandfather's and there's just something cool about being able to turn the key on a 40+ year old unit and drive it anywhere at any time with the original engine. That's the point to which I have gotten it, and I would like to continue the theme by improving it little by little each year.
 
DRTDEVL said:
Indeed I would. If the 8.1 fit in there nicely, it would be an option, but the rails are too narrow for an easy swap.

I have even considered getting a wrecked 94-95 Ram 3500 2x4 Cummins for a donor truck and swapped the entire front end under it, along with the entire drivetrain (axle, too), but then we're looking at a MONSTER doghouse. Perhaps better off thinking 6.2/6L80e(?). In the end, this RV was my grandfather's and there's just something cool about being able to turn the key on a 40+ year old unit and drive it anywhere at any time with the original engine. That's the point to which I have gotten it, and I would like to continue the theme by improving it little by little each year.
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So small turbo setup? :flipoff2:
 
DRTDEVL said:
Indeed I would. If the 8.1 fit in there nicely, it would be an option, but the rails are too narrow for an easy swap.

I have even considered getting a wrecked 94-95 Ram 3500 2x4 Cummins for a donor truck and swapped the entire front end under it, along with the entire drivetrain (axle, too), but then we're looking at a MONSTER doghouse. Perhaps better off thinking 6.2/6L80e(?). In the end, this RV was my grandfather's and there's just something cool about being able to turn the key on a 40+ year old unit and drive it anywhere at any time with the original engine. That's the point to which I have gotten it, and I would like to continue the theme by improving it little by little each year.
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4bt. :flipoff2:
 
Dodge trans suck, I can't really see any reason to want to stay in that brand.

440 big block is cool but at the current tune, (maybe even new) it is less powerful than most 1/2 ton truck powerplants.

FI will help a lot of stuff for driveability etc. but may make zero difference on MPG or total power.

I have similar problems with my planning of my sons 1965 F100 with FE 352, cool old iron, sucks at every category (compared to the last 20 years offerings)
 
CarterKraft said:
FI will help a lot of stuff for driveability etc. but may make zero difference on MPG or total power.
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This is where I would disagree. It currently has a pig of an 800 freaking cfm Carter Thermoquad on it. It literally dumps fuel in there, and even when fully leaned up on the tuning, it still smells a bit rich and hot starting? Gotta floor it to open the secondaries so enough air can get in to fire it up. If I could get it to stay close to stoichiometric, I bet it would use an awful lot less fuel. I'm not expecting any noticeable power gains, just fuel economy improvements and fixing the hot start issue.
 
posford said:
So small turbo setup? :flipoff2:
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I have absolutely zero knowledge on how to set something like that up, although it would be pretty cool. The biggest issue I would see with that, however, would be that it doesn't seem to be along the lines of my goal, better economy. It would pull the hills like a freight train, though.
 
DRTDEVL said:
This is where I would disagree. It currently has a pig of an 800 freaking cfm Carter Thermoquad on it. It literally dumps fuel in there, and even when fully leaned up on the tuning, it still smells a bit rich and hot starting? Gotta floor it to open the secondaries so enough air can get in to fire it up. If I could get it to stay close to stoichiometric, I bet it would use an awful lot less fuel. I'm not expecting any noticeable power gains, just fuel economy improvements and fixing the hot start issue.
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If that is the situation then I would agree. A correctly functioning Holley vacuum secondary though might be tougher to compare.
 
DRTDEVL said:
I have absolutely zero knowledge on how to set something like that up, although it would be pretty cool. The biggest issue I would see with that, however, would be that it doesn't seem to be along the lines of my goal, better economy. It would pull the hills like a freight train, though.
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Engine running at 50% load should pull less fuel than at 80% load
 
posford said:
Engine running at 50% load should pull less fuel than at 80% load
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Engine making 350 hp will entice my right foot to lean in harder on the hills than engine making 175 hp.

And at 50% load... how much more fuel potential is there to be used when doubling the power? That would use 50% of double, or roughly the same.
 
My .02 is fi tech sux on my buddies dauntless.
my 22r to re swap (same block) did ZERO for mpg (deliverability yes)
the newer auto will help more.
 
I'll agree going from a properly running carb to a EFI will make no difference in MPG on a motorhome.
The issue with the dodge motorhomes home is they were just so damn gutless you spend most of your drive with your foot on the floor.
A 440 motorhome is cool, if you were wanting to keep it for the long haul, I'd rebuild the engine and do some headwork so i made some decent power. An overdrive transmission is always nice too, I'd rather have that than a gear vendors.
 
welndmn said:
A 440 motorhome is cool, if you were wanting to keep it for the long haul, I'd rebuild the engine and do some headwork so i made some decent power. An overdrive transmission is always nice too, I'd rather have that than a gear vendors.
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This thing will be with me until I pass it on to the next generation. I store it indoors and it now has completely modernized systems (fridge, inverter, batteries, ac, 16" wheels, etc.). I went camping with my grandparents in it, and someday my grandchildren will do the same.

I have considered building the engine, but most of what I find on 440 builds is for hot rods, not torque monsters. From my reading, the current pistons might not even come all the way up to the deck, so that is a concern with just doing head work.

The transmission isn't in the cards this year due to time constraints, but I think I can go EFI pretty quickly, especially considering I already have to drop the fuel tank in order to replace the filler vent hose (rotted and leaking).

As for the lack of power bit, I rarely open the secondaries going down the highway, only on the bigger hills. Last year, a large Fleetwood Southwind Class A went barreling past me on I 90... but then we came upon a hill. I held 60 on the way up (pulling the trailer setup in the pic above), while his 454 was screaming like hell, bleeding off speed. He roared past me coming down the other side of the hill, but the same thing occurred on the very next hill. We traded positions like this for about 30 minutes in the rolling hills between Wall and Rapid City before it leveled off enough for him to pull away. This RV is small enough where it does not have a power to weight ratio problem.
 
You modernized the internals....

but you don’t want to modernize the drive train. Makes no sense.

LS/6L80.
 
DRTDEVL said:
I love the smell of non-catalyzed exhaust in the morning. Smells like... the good old days
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Then you’re in a catch 22.

you want modern fuel economy without modernizing....
 
DRTDEVL said:
Realistically, what would an LQ4 and 4L80e combo get in an RV of this size and aerodynamic profile? 8? 9?
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you started a thread asking for advice to increase mileage.... but then you don’t want the answers.

What’s thousands of $$$ in EFI and trans/od upgrades going to get? Hint: less than a modern engine/trans swap.

so... what do you really want?
 
Don't know much about Dodges, but did they make a 440 with more torque/horsepower with a O/D transmission you could swap for less than the cost of that EFI? You could probably sell your engine and trans to someone else and recoup some of your money.

Edit: I dig the RV, we had one when I was young and I drove it when I got my learners permit while my my dad drank beer in the back. It needs some type of crazy graphics and/or paint.
 
BDK said:
Don't know much about Dodges, but did they make a 440 with more torque/horsepower with a O/D transmission you could swap for less than the cost of that EFI? You could probably sell your engine and trans to someone else and recoup some of your money.

Edit: I dig the RV, we had one when I was young and I drove it when I got my learners permit while my my dad drank beer in the back. It needs some type of crazy graphics and/or paint.
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More power? Yes. OD? No
 
DRTDEVL said:
and fixing the hot start issue.
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It may not fix that. Most throttle body set-ups are dead head fuel lines. The fuel will boil just as easily with those lines as with the carb lines. You will just have a better pump to push all that vapor through. An electric pump would offer the same thing to the carb set-up.

When I was a kid my dad went through the 440 in his motorhome. Ported heads, cam, intake, headers, pistons. Got about the same mileage, we were just going a lot faster.
 
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