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Old 10-03-2012, 03:04 AM   #1 (permalink)
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New guy with a 1970 Ultravan classic RV

Hi,
My name is Larry Forman and my wife and I own a 1970 classic RV called an Ultravan. It is 22 ft. long, by 8 ft. high and wide. Most of these have a Corvair powertrain, which is a 1960's Chevy air cooled aluminum flat 6 engine. Despite these engines being VERY small for an RV, they actually work because these are relatively light weight RVs. This is because they were designed by an aircraft engineer and have NO chassis since they are monocoque construction similar to an air plane with aluminum skins and C channel supports. The horsepower to weight ratio for most of these Ultravans is very close to any RV on the road today, but they are more efficient. My particular Ultravan came from the factory with a 307 c.i.d. Chevy engine, HOWEVER before I got it, it had been converted to an Olds Toronado 455 c.i.d. 375 horsepower entire power train moved to the back from an original Toronado f.w.d. All this makes for a VERY unusual RV and it has a retro look. Do a google search for Ultravan for more information and photos.

As an Electronic Engineer, I look for ways to improve the mpg of this vehicle and currently run about 12-13 mpg for long trips, which is not bad considering the vehicle and engine size. This engine has a Holley carb and is not fuel injected (currently). My interests are to improve the fuel economy to about 15 mpg, if possible and practical.

My specific immediate need is for an mpg gauge for this carburetted engine. Does anyone know where I can obtain or build one, ideally like a MPGuino for carb engines? I suspect some of the hot rod guys might have similar needs and requests.

Many thanks for any assistance and I find this entire site very interesting with lots of applications to what I want to do.

-- Larry Forman

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Old 10-03-2012, 03:29 AM   #2 (permalink)
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I lust for one of those! I'd consider a 3800 GM heart transplant; those drivetrains are good for nearly 30 mpg and make very good power.
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Old 10-03-2012, 04:16 AM   #3 (permalink)
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Welcome to ecomodder.

They're already pretty smooth as RVs go.

https://www.google.com/search?q=ultr...w=1411&bih=625

What's the underside like ?
On some pics, it looks like they already have some sort of belly pan to smooth out the underside - though it could be improved a bit.

Does your UltraVan have lots of stuff hanging on the sides or on the roof ?

However, increased tyre inflation and changing / improving the way you drive it would probably be the most effective changes.
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Old 10-03-2012, 01:29 PM   #4 (permalink)
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You are correct about the underside, which has three aluminum tanks that are relatively flat. My exception is that I added an air dam a few years ago when it had a tail happy issue at high speeds or when trucks passed. That has been solved so I need to consider if the air dam helps or hinders gas mileage.

I also have started driving about 55 mph for long trips and that alone helped a ton. Also I added a vacuum gauge to assist in keeping my foot off the gas pedal.

What I REALLY need is an instanteous gas efficiency gauge to help me determine how to continue improvements and to evaluate changes, e.g. removal of the lower air dam, adding a cold air intake, increasing tire inflation, etc. I already have LRR tires but need to fix an intermittent sticking brake pedal that does not always return to full up and causes dragging brake pads.

Thanks for the suggestions. -- Larry
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Old 10-03-2012, 01:53 PM   #5 (permalink)
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Tachometer, vacuum gauge and fuel flow meter. Those three will do a lot, though the latter is expensive. I'd pre-heat the engine/trans in advance of any trip (electric heaters).

Fuel injection will make the biggest difference. Steady-state cruising won't be all that different (short of major altitude changes), but start-up & warm-up will be under control in ways carbs can't handle. The engine should show longer life and reduced oil consumption as well.

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Old 10-03-2012, 03:34 PM   #6 (permalink)
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Thanks! I have a tachometer and just need to run the wires to make it work. I DO want to add an instaneous mpg gauge to help determine how to maximize going up and down hills.

The tach will tell me where I am on the rpm-torque curve. I have the possibility of adding a solenoid switchable variable vane on the tranny torque converter to lower rpms approximately 200 or so, like about a half overdrive. I need to determine if the added cost is worth the possibility of improving fuel economy.

Since I am hauling approximately 7,000 lbs, I cool the tranny and engine oil to keep everything within reasonable thermal limits. I am running four radiators(!) - two are full sized with the rearmost one having two flex fans cooling it and electric fan for the other large radiator. Two small heater core radiators need shrouds to improve air flow and cooling. I want to replace the flex fans with electric fans to lighten engine belt loading.

I have an air dam below the front and an air scoop ahead of and below the engine. I wonder if these help or hurt mileage and a mpg gauge will let me test any changes. Also, I wonder if the temps of the air below the body might be higher than I want, from the pavement being solar heated. I would like to add a ram air scoop for the carb and see if the engine breathes better.

I want to test the rolling resistance and Cd to obtain a baseline, then make changes and see what improves.

I can increase the tire pressures on the LRR tires. I want to see if I can get close to 15 mpg on this engine combo and I am now close to 13 mpg, which is not too bad for 7,000 lbs and a 375 hp 455 carb engine. Lowering rolling weight can also help. I have already lowered the weight by several hundred pounds with several hundred more to go. I added rear air suspension which enabled me to remove the rear boat anchor of the heavy rear subframe and torsion bars. I can add front air suspension to eliminate the steel front coil springs. Adding powered rack and pinion steering from an '08 Silverado 1500 will enable better front tire alignment with reduced tire wobble and easier steering while parking. I don't know if running full synthetic oil will help or not. The engine and tranny have been rebuilt about 55,000 miles ago and the cylinder compression is very good at 180 pounds for all 8 cylinders. I am running Ignitor III ignition with very hot Accel ignition coil, so the ignition is good. The Holley carb has been rebuilt.

Thanks for the tips. -- Larry
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Old 10-08-2012, 09:52 AM   #7 (permalink)
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The engine is likely closer to 250HP in actual trim. The "true" numbers don't matter much as it is a torque motor, in main. Find the correct HP/TQ graph (year of production) to see where the TQ peak is located. The old rule-of-thumb from the 1960's & '70's was that cruising rpm should be just below peak torque. Fewer throttle changes this way (rolling terrain) and the engine tends to run coolest, overall. Axle gearing (expensive) and tire height (rolling height) are the places to concentrate so as to get best bang for buck from tires.

EDIT: the ACCEL coil is likely not optimal for the low rpm engine you are running. I'd dump it in preference for what MSD offers (if asked with information at hand about rig). Even a stock DELCO piece would be better. And the QuadraJet can be modded for part-throttle adjustments that are crucial, IMO, for highway economy in heavy vehicles. And using an adjustable kickdown for that TH425 trans is a good idea (dial it in).

Last edited by slowmover; 10-08-2012 at 11:28 PM..
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Old 10-08-2012, 03:08 PM   #8 (permalink)
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I don't think a lock up torque converter would be a good idea in something that heavy with that much torque. If you only engaged it on the flats at cruising speed it probably wouldn't hurt anything, but that big 455 twisting against 7000 pounds will murder the transmission on any kind of hill with the converter in lockup.
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Old 10-08-2012, 08:40 PM   #9 (permalink)
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Quote:
Originally Posted by War_Wagon View Post
I don't think a lock up torque converter would be a good idea in something that heavy with that much torque. If you only engaged it on the flats at cruising speed it probably wouldn't hurt anything, but that big 455 twisting against 7000 pounds will murder the transmission on any kind of hill with the converter in lockup.
Get a MT out of an old rear engine bus problem solved.
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Old 10-08-2012, 09:01 PM   #10 (permalink)
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Quote:
Originally Posted by War_Wagon View Post
I don't think a lock up torque converter would be a good idea in something that heavy with that much torque. If you only engaged it on the flats at cruising speed it probably wouldn't hurt anything, but that big 455 twisting against 7000 pounds will murder the transmission on any kind of hill with the converter in lockup.
Dry weight 3-4000 lbs; touring weight 4500-5800 lbs.

A Buick Park Avenue's curb weight can be 3800 lbs. They have lock-up converters. Come to think of it, full-size pickups do too.

I wonder why this one weighs 7000 lbs when the Ultravan site says what I quoted above?

If a little Corvair engine can move that thing down the road, I'm sure a nice GM 3800 engine/trans combo with OD and locking converter would move it down the road even more nicely, and who knows, maybe it could break into the 20's mpgs.

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Last edited by Frank Lee; 10-08-2012 at 11:52 PM..
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