What's new
By:
Filters

Fuel economy ideas for an old RV

I got 12.3 mpg empty in a 5.3 Tahoe Sunday rocking 600 plus miles with a lead foot . I’m not sure what you’re thinking you can gain and if willing to lose 1400 to a fitech setup for the minimal gain if any you might see to do so but you need to be honest and realistic with yourself . You’re not going to get decent fuel economy with that dinosaur and if you want something with more power or economy you need to sell it and buy something else or accept the gas tax and rock it til it’s wheels fall off . If you’re getting 5.5 towing now and 7.5 empty let’s just pretend you’d get 10mpg empty and 8 mpg towing you’d save a messily 215 dollars from Austin to sturgis over the course of 1261 miles or 430 round trip . Personally I’d say it’s time to upgrade .
 
Leadfoot21 said:
I got 12.3 mpg empty in a 5.3 Tahoe Sunday rocking 600 plus miles with a lead foot . I’m not sure what you’re thinking you can gain and if willing to lose 1400 to a fitech setup for the minimal gain if any you might see to do so but you need to be honest and realistic with yourself . You’re not going to get decent fuel economy with that dinosaur and if you want something with more power or economy you need to sell it and buy something else or accept the gas tax and rock it til it’s wheels fall off . If you’re getting 5.5 towing now and 7.5 empty let’s just pretend you’d get 10mpg empty and 8 mpg towing you’d save a messily 215 dollars from Austin to sturgis over the course of 1261 miles or 430 round trip . Personally I’d say it’s time to upgrade .
Click to expand...
$215 for Sturgis. Another $100 for our annual Wisconsin family trip. We were also wanting to take a family trip up to the north shore of Superior every year (probably to start next year) for another $150 in savings. That's $365/yr minimum in savings... and I am thinking it would be a lot more comfortable of a drive if I take rockota 's route and go 6.0/6L80e, since I could then cruise at the speed limit, rather than 60 all the time. If it were more economical and comfortable, we'd use it a lot more than we currently do.
 
A Ford 5.4 or Chevy 5.3 would run circles around that in both the fuel economy and power department. :lmao:
 
4BT might get you mileage at the same speeds.

Keep it Dodge and do some sort of HEMI swap?
440 can make a bunch of power, not usually associated with great mileage.
 
This Indy 440 makes 540 lb ft @ 4300 rpm and 550hp @ 6000 rpm.
that would be pretty awesome

INDY CYLINDER

indyheads.com
1625056368790.png
 
DRTDEVL said:
$215 for Sturgis. Another $100 for our annual Wisconsin family trip. We were also wanting to take a family trip up to the north shore of Superior every year (probably to start next year) for another $150 in savings. That's $365/yr minimum in savings... and I am thinking it would be a lot more comfortable of a drive if I take rockota 's route and go 6.0/6L80e, since I could then cruise at the speed limit, rather than 60 all the time. If it were more economical and comfortable, we'd use it a lot more than we currently do.
Click to expand...
I love living rent free in peoples heads. :flipoff2:

unless you go whole hog on a nice 4bt/4l80, the 6.0ls/6l80 pullout is probably the cheapest, easiest, fastest option.

having said that, the 4bt would be killer.

almost would suggest a 6.8 as well, since they were used in many RV’, but not sure that would fit.
 
DRTDEVL said:
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.
Click to expand...

Start with the free or nearly free stuff first. Do you know what the timing is at right now? It is probably retarded beyond belief being an 80s smog era motor. Definitely recurve the ignition, It'll make a noticeable difference. Worst case it'll pick up some power.

There's no reason you shouldn't be able to dial that thermoquad in better. How are you getting the secondaries to open when cranking? They are vacuum secondaries. Sounds like a little carb tuning would go a long way. The thremoquads and quadrajets will give better MPG than a similar holley/edelbrock so I wouldn't necessarily swap it for a holley. You could pick up a wideband O2 sensor if you really want to get it perfect.

That 440 really needs some compression and more cam, but i bet there is an MPG or 2 in it for under $200 and some time tuning.
 
The amount of advance that 440 will take with it’s terrible heads will be extremely disappointing. Be very careful not to advance it too much, it will ping like crazy under acceleration.
Just tune it up and drive it.
My 2009 Chevy 2500HD 6.0/6L80 has never done better than 13 unloaded. Any swap is not worth it, I don’t know anyone who likes their FI tech setup.
Sounds like you already love it for what it is, keep that attitude and have fun.
 
welndmn said:
I'll stand out, LS swaps are dump, keep the big block, it's cool.

For reference, my 28' class C with Ford v10 and 6 speed auto still gets 8-9mpg.
Click to expand...
8 is 25% better than 6 though.

That's like the difference between 24 and 30 or 30 and 40.

When you're talking about RV fuel economy 25% is a huge decrease in cost or increase in range.
 
LS swap is stupid or not but you can not beat the OEM improvements that have been made.
Roller cams, Cylinder head geometry, gasketing, Long tube intakes, etc.

If you can bolt up a OD trans to your block with no drama that seems like the correct move regardless of FI, whatever.
 
Mind you I've never owned a 440 or a motor home, but the rattling in my head says this...
Adapta kit for a 4l80 with manual valve body and a floor shifter with lock up and OD switches.
Find some pre-smog heads, a stroker kit and up the compression with a hottish ignition.
Edlebrock 28155 manifold, injectors and rails with some kind of throttle body and your pick of computer.
6.0 and 4l80 swap. Check with "burndown" and "fuel injection sucks" on the toobe of u for LS motor home turbo swaps.
 
i had a 440 rv. an american clipper. puling 16ft enclosed with dirt bikes and quads i'd get 4-5mpg... i don think your going to gain much from where you are at, od trans is all i'd do.


but really, i'm with rockota. and whoever else thats suggested a newer take out combo. if you want this to be an heirloom vehicle, you need to keep modernizing it. i think your throwing money away doing anything with the current drivetrain.
 
jeepnmatt said:
www.hotrod.com

440 from a Winnebago Dyno Tuned at Westech Performance

The Steves and Freiburger hang a low-mile 440ci big-block Mopar engine on the dyno at Westech and prove they are perfect for muscle-car swaps!
www.hotrod.com www.hotrod.com

Engine Masters and Roadkill has done work on some RV 440's. You might learn some tricks from watching some of those episodes.
Click to expand...


Interesting that they ran 41⁰ total timing in their stock 7.5:1 440, yet someone earlier commented that I wouldn't be able to push 38⁰ on a low compression engine without pinging.

Also of note, I asked in the past for guesses on power output, and that stock RV 440 was in the neighborhood of 320 hp and 450 tq with no power mods and the factory 800 cfm Thermoquad like mine. Most of the guesses here were in the 175 hp range, so this is encouraging news on the OD trans front... especially looking at that torque curve. It looked to stay north of 445 from somewhere down low all the way past 3500 rpm. That's more than enough to maintain speed in OD. Compare that to the max torque of an LQ4 at 370 and the LY6 at 385, and this 440 suddenly seems like the better option again.
 
In real life, in a motorhome, you can’t avoid low RPM, WOT conditions. That is when your engine will detonate.
 
if you hate the thermoquad so much then just slap an AFB on it, or a quadrajet if you're a GM guy
to get your cruise AFR dialed in you can toss a pyrometer at it and use a cut up propane torch to toss extra fuel at the intake for testing purposes
iirc you adjust fuel mixture for high EGTs, airplane guys are the ones to talk to on that particular tangent
pyrometer is my suggestion over a wideband because widebands are very fragile and expensive, I go through sensors and controllers fairly often in my megasquirt car

garbage can chinese FI conversion is a mistake, if it is a toy that you can haul back home when it dies, thats one thing, but a tow bill on this pig would be hard to swallow

Modern engine and trans is going to be the best way to get OD and lockup, and the GM shit is the easy button.

for fuel economy, focus on aero
a coroplast air dam and side skirts may look dorky, but its likely to be your best bet for gains.
skirt right over the rear wheels if you can
folding tailcone like the semis got will make a difference, too.
 
Projectjunkie said:
I could never stomach $1500 for efi and 2k for overdrive when you can buy an ugly auto 2nd gen dodge for 3k and Cummins swap it
Click to expand...
I have run this situation through my head, and its not a feasible swap. The 440 is 30 inches long and uses nearly every available inch of space in the doghouse. The 12 valve is 40 inches long, meaning I would have to extend the doghouse nearly a foot further into the cab, and its already up to the seats. This would take up all the space between the front seats and make it difficult to get in and out of the front seats from the coach body.
 
DRTDEVL said:
I have run this situation through my head, and its not a feasible swap. The 440 is 30 inches long and uses nearly every available inch of space in the doghouse. The 12 valve is 40 inches long, meaning I would have to extend the doghouse nearly a foot further into the cab, and its already up to the seats. This would take up all the space between the front seats and make it difficult to get in and out of the front seats from the coach body.
Click to expand...
FWIW, maybe compare it to a similar era ford, I know of 2 successful econoline class c 12v swaps, but, those were also specd for an inline 6...



I would explore the LS auto swap, I'm cheap and would gravitate to the earlier with the 4l80e, but the newer 6 speed is proven, and that slug could really use the gears
 
DRTDEVL said:
I have run this situation through my head, and its not a feasible swap. The 440 is 30 inches long and uses nearly every available inch of space in the doghouse. The 12 valve is 40 inches long, meaning I would have to extend the doghouse nearly a foot further into the cab, and its already up to the seats. This would take up all the space between the front seats and make it difficult to get in and out of the front seats from the coach body.
Click to expand...
4bt
 
Realistically, no matter what you do you're going to be in a similar mpg situation.

I'm in the same boat, however I recognize I'm not really going to get better gas mileage. My main goal is to make my rig not miserable to drive. Like, I can't tow and have the a/c on at the same time. Fuck that. If I'm going to get 7-8mpg, I need some power in there to make it worth it. In all reality, it doesn't much matter which gas engine is in there, there's not going to be enough change to justify the cost. Fix it up for drive ability and keep your wallet handy.
 
Ummduh said:
Realistically, no matter what you do you're going to be in a similar mpg situation.

I'm in the same boat, however I recognize I'm not really going to get better gas mileage. My main goal is to make my rig not miserable to drive. Like, I can't tow and have the a/c on at the same time. Fuck that. If I'm going to get 7-8mpg, I need some power in there to make it worth it. In all reality, it doesn't much matter which gas engine is in there, there's not going to be enough change to justify the cost. Fix it up for drive ability and keep your wallet handy.
Click to expand...
Driveability is one of the concerns being addressed with the OD trans path... allowing reasonable RPM of around 2200 at 65 (2400 at 70), rather than a big block screaming at 2900 RPM at 60. I'm sure the engine has more than enough torque to push those speeds in OD.
 
If an inline 6 turbo diesel is off the table because of engine bay length, a 7.3/4r100 swap, or a duramax swap could be really doable, especially since you know where to find donor vehicles:smokin:

Alternately, you got room for a 3rd pedal?

Fresh heads/ carb/ ignition and a 4 or 5 speed could do the trick

I loathe the idea of a non lockup 3spd turning $3 gas into heat and noise
 
DRTDEVL said:
Driveability is one of the concerns being addressed with the OD trans path... allowing reasonable RPM of around 2200 at 65 (2400 at 70), rather than a big block screaming at 2900 RPM at 60. I'm sure the engine has more than enough torque to push those speeds in OD.
Click to expand...

My rig generally won't pull or even maintain speed once it's in OD unless it's really flat or downhill. We're probably similarly powered, I have a 95 F250 460/e4od, 4.10s and a 26' fifth wheel. Stock ratings were 245/400. I run 3500rpm at 70 in 3rd, 2500 in OD at 75. Also running 3500 rpm in 3rd really causes the trans to heat up.
 
Wizzle said:
I haven’t ran the numbers on cost to operate compared to money spent on swapping but it usually doesn’t seem worth it in the end unless you put some serious miles on the vehicle.
Click to expand...
Today, it's $3/gallon.

What will the price be in 20 years? 40 years? 60 years?

This isn't a disposable item. Its been in the family since new, and will remain so.
 
You must log in or register to reply here.
Top Back Refresh