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Old 11-07-2016, 12:54 AM   #1 (permalink)
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New member working on a vintage class C RV


I have been lurking here for years and silently cheering on everybody who's working to get better F.E. out of their rides, and I finally have a project worthy of tackling.

It's a 1980 American Clipper 21' Class C RV. Super cool, a one family owned timewarp. The plan is to make it reliable and fun, and make some modifications along the way to help improve it's efficiency.

I have amazing records from the first owner of nearly every fillup which average out to 7.5 MPG over 76,000 miles. He never did anything to improve the FE other than trying to keep it in good shape.

As for me, I'm a lapsed Engineer, and was on the first Super Mileage Vehicle team at UC Berkeley back in 1992. I think we were averaging around 3000 MPG before we broke due to lack of testing. The team the next year finished and put in a respectable result if I remember correctly.

I'll get a build thread started soon, but thought I'd introduce myself first.


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Old 11-07-2016, 07:47 AM   #2 (permalink)
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I'm glad you signed up.

Wow, you've got a lot to overcome there:

I'd probably start with fairing the top with coroplast and doing as much of an aero tail as is practical:

On the plus side, every smidgen you gain is a huge percentage gain!

Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

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Old 11-07-2016, 08:28 AM   #3 (permalink)
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Holy COW. Now...THAT is an uphill battle.

When you start your build thread, I'm going to definitely subscribe to that. And, FC was right on the button. If you get it to 10 mpg, looked at one way it's a mere 2.4 mpg improvement, looked at the other way it's a 33% improvement.

Hmm. I don't think the EPA posted ratings for RVs, so we're just going to have to go with the vehicle's own history as a baseline.

Lead or follow. Either is fine.
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Old 11-07-2016, 04:50 PM   #4 (permalink)
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Thanks for laughing with me guys, yes uphill battle is an apt analogy. Just thinking of driving this uphill over the coast range gives me goosebumps. We've delayed a maiden voyage twice now as I haven't been ready.

Last night I dug out a great article I found a few months back about trying to improve fuel economy on an 80's 4x4 dually Ford with a 460. They didn't touch aerodynamics, but did improve FE significantly with small, but measurable improvements. So I'm starting with that approach, find stuff that's measurable and make small improvements.

I also have other goals such as keeping the engine heat managable, making it handle better (no swaybars from the factory, ah the 70's), tightening the steering, etc.

And of course I know that driving it at 55 vs 65 will make the biggest difference. Thankfully for now with a 3 speed, unlocked transmission she's probably pulling 3000 RPM at freeway speeds. That's loud when the big block is sitting next to you. Putting in the overdrive trans will be more for livibility than actual cost savings.

We also did the calculation of car/hotel, vs truck/trailer (we had a 2004 Tahoe and 66 Streamline trailer previously that averaged 12 MPG towing, not bad), vs an old RV vs. a newer RV. We decided the $10k we saved going with the cool, old RV bought a lot of gas, as well as lots of room for upgrades. Plus we don't have as much money sitting in the driveway depreciating.

elhigh, I think most people just look at 1 MPG as 1 MPG. But for me it's all about the relative increase. While I probably won't notice the difference between 25 or 26 MPG in our Benz, going from 7 to 8 in the RV would be over a 10% difference, possibly up to $10 off a typical $100 fillup.

It's a 50 gallon tank, most gas stations cut you off at $75. Fun.

Anyway thanks for laughing along.
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Old 11-07-2016, 05:37 PM   #5 (permalink)
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I think a 7004r or what ever has replaced it would be a good place to start, had a 350/350 turbo in a S-10 blazer 4x4 (3.73s), went cheap to get it running and upgrade later with a fresh 350/700r4 went from 12-16 mpg. $700 tranny never did pay for itself but made it a more pleasant drive.

Or really update it and find a wrecked truck for donor engine and tranny.

Last edited by roosterk0031; 11-07-2016 at 05:49 PM..
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Old 11-07-2016, 07:31 PM   #6 (permalink)
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Exactly. I don't expect the trans swap to pay for itself, it's more the point that this thing is designed for road trips, so we need to make it road trip friendly. The options are either a Gear Vendors OVerdrive, which I would LOVE. But costs about $3000.

Or find an A518 out of an early 90's van, rebuild it, shorten the shaft in the RV and install it. Not plug and play, but we can make it work. My understanding is the A518 is basically a 727 with added overdrive. I'm not planning on climbing hills in OD so I'm not worried about blowing it up. Plus I think I can get a used trans, rebuild it and install it for $1000-$1500. Half the cost of the GV overdrive.
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Old 11-07-2016, 08:52 PM   #7 (permalink)
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Old 11-07-2016, 09:09 PM   #8 (permalink)
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My parents just bought a very similar rv earlier this year and drove around the country with it over the summer. I think it was a 26' Shasta on a chevy chassis. 350 small block but with a 3 speed no o/d. I think they got around 6mpg.

Aero is going to be easy as cake to improve on that thing but i will say with that age, dont forget to fix the a/c.

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Old 11-07-2016, 09:15 PM   #9 (permalink)
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What engine is in the camper? 400?, 383?, 360?, 0r 318? My bet is that it is a 360, which was a stroked 318. IIRC, those were carburated engines that tended to carbon up the intake manifold. Those are solid engines. Why not update it with port injection? I don't see why you need to replace the engine. Just update the torque converter with one that locks up (1982 or 83 model ?). What is the rear axle ratio?
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Old 11-07-2016, 09:31 PM   #10 (permalink)
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My thoughts on RV aero include tackling the many protrusions that likely contribute to drag all out of proportion to their relatively small size, like roof a/c, roof racks and pods, that yuge canopy on the side, giant mirrors-on-a-stick, various antennae, and so on. Do some soul searching and decide if deletes are something you wouldn't mind?

The aero tail as Charlie mentioned should be an effective mod, perhaps the best one of all. Air dam could help too.

Non-aero thought: weight. Or more specifically, weight reduction. I've been to enough camper ralleys to know that many people pack everything including the kitchen sink. I think travelling light could only help. Things like, do we really want to fill the water tank when the destination has showers and whatnot? Lots of weight there.


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