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Old 03-21-2015, 04:58 AM   #15
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1975 20' Argosy 20
Manston , Kent
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When comparing mileage are you also considering the difference between the US gallon (3.79 litres) and the Imperial gallon (4.55 litres)....a gallon is 20% bigger in Europe so you should be getting more miles per 'gallon' not less.

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Old 03-21-2015, 01:54 PM   #16
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1982 28' Airstream 280
Port Angeles , Washington
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Originally Posted by Roquefort View Post
Thank you "Smartstream" for your details answer.
If there is no "Lock-up" in the stock converter, and the only change we made is from stock to the Allison Converter, WHY is the gas cosumption that high now ?????
Any idea ???? Your gas mileage with the ISUZU Diesel is wonderfull, will never get this with the V8 gas Chevy. Also the rpmīs you drive at highway speed seems to be different to the gas model, am i correct? Anyhow, 5.3 MPG is more than terrible, WHERE is the default..?!

I also decided to buy the "Gear-vendor" under-/ overdrive unit, but the costs are very high. Not only the purchase, but also the labour here in Germany and shipping of the parts. In addition to this the Euro (€) became very weak and this will raise the costs again.
We donīt drive a lot per year, because of missing time. just about 4000-5000 mls...!
My thought was to install a LPG system from IMPCO, this is very interesting here, because the LPG is just 1/3 as the price of the gas.
I would guess the biggest difference is the type of driving. Stop and go traffic or small town driving is real killer to mileage in these type of vehicles. I would guess you don't get out on open highways for many miles like in the States. Also it is very difficult to get accurate mileage from one or two tanks. Calculating the mileage over several tanks of fuel or several thousand miles would be a better comparison.

The diesel mileage is great but we sacrifice power that you have in the gas engine. The diesel is slow in the hills. I believe these coaches all have 4.56 gears in the rear axle so with the same transmission rpm should be the same. The big difference is the max rpm for the diesel is 3400 so the top speed is about 66 to 67 mph. That is why the Gear Vendor unit is so nice in the diesel. It is expensive but as I said before all the modifications are expensive and the number of miles you drive is a consideration. The LPG conversion may be the best choice for the money.

Owning one of these coaches is expensive but in the end it is the cost of entertainment. If you don't spend it on the Airstream you will probably spend it somewhere else. Only you can decide what you enjoy more.

Cheers, Dan

"Socialist governments traditionally do make a financial mess. They always run out of other people's money. It's quite a characteristic of them."
~ Margaret Thatcher ~
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Old 07-10-2015, 04:27 PM   #17
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1984 34.5' Airstream 345
Foothill Ranch , California
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My opinion....

Just to be clear, the 454 is a torque monster, but never efficient with fuel.
My 7000 mile old Jasper rebuilt 454, with banks exhausts, but an Edelbrock Carb, and pancake air filter did between 6.5 and 8.6 mpg on its 1600 mile maiden journey. The 8.6 was a freak I believe. The 7mpg quoted is a real world figure if you drive carefully and the engine is optimized.

My TBI injected 454/TH400 powered Suburban which weighs a whole lot less, and had a whole lot less frontal area to push along than the Airstream at 6000lb would never break 12mpg.
Weight kills you getting up to speed, or on hills, and frontal area kills you at cruise.

People with the Cummins 5.9 in the same rig report 12/15+ mpg.

The transmission in these Airstreams is a TH475... which is close to a TH400 but stronger as it has some upgrades. Neither have a Lockup converter, so they slip a little or a lot and that hurts gas mileage.

If you need fuel efficiency my advice... if TUV allows it... put a diesel in there. Maybe a VM or other European model. The cost would be high, but you could spend almost as much putting fuel injection, and a Overdrive/Lockup transmission or Gearvendor in, and it STILL would rarely break 10mpg.

If that is not an option...
Fuel injection can be cheap(a used TBI setup could cost you less than $500), or an aftermarket Injection setup at $3000 will gain you 1 or 2 mpg.

For transmissions look to spend $3000 or more on a gearvendors, or a 4L80E/4L85E which will gain you 1 or 2 mpg.
Both prices are excluding fitting....

Here is your calculation for the day...
Airstream Miles/Km driven per year... Divided by Mpg/L/100km... times fuel cost.
Then look at what you need to spend to gain 2mpg/4mpg/6mpg....
I tell you, it buys a lot of fuel...
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Old 07-10-2015, 04:34 PM   #18
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1975 20' Argosy 20
Manston , Kent
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Another option that is quite often taken in the UK is the LPG route. Although the mpg is about the same, the cost of fuel is less than half. Take a look at Propane Conversion Kits by Nash Fuel
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Old 07-13-2015, 03:16 PM   #19
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1984 34.5' Airstream 345
Foothill Ranch , California
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Good point Martin... I have been mia from Europe for 15 years so am out of touch! I think the stock propane tank is 100lb plus...
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Old 07-16-2015, 01:33 PM   #20
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1975 29' Ambassador
1986 34.5' Airstream 345
Grefrath/ Germany , NRW
Join Date: Jun 2013
Posts: 181
Tas mileage

Thank you ALL very much for sharing your thoughts!
I agree, the 454 V8 n a 345 classic is allways a "guzzler", but i still do not understand this significant difference between the trip in Amerika (8,5 mpg) and the travels on the roads here in Germany (5,5 mpg...!).
While i understand, the open roads in Amerika are much easier and better to drive, then the small roads here, i still "abused" 5,5 mpg on a freeway trip by night from Cologne to Hamburg (about 280 mls). I was @ a cruisespeed of 55-60 mph, engine was @ 2600-2800 rpm.
Anyhow, if you want to play, you need to pay!
Changing the engine is not an option, she runs PERFECT, i love this wonderfull deep V8 music from my Banks-system !!!
The gearvendor overdrive could be an option, but not for now.
I will switch over to an IMPCO lambda controlled LPG system, with a capacity of 100 US gallons. I will remove the "bathtub-like" gasolintank, and install instead a 30 gal. "Emergency-tank". The free space will be used by 2 giant Propanetanks!
I allready bought a propanekit for my generator, i need it, because the cab AC is to weak to cool down the rig on the road! Thank you for the link to Nash-fuel, i knew him allready, it is a reliable and "good" company!!!
One last question:
If i decide to install a new or maybe used TBI intake kit, is my BANKS system still "up to date"? I bought it exspecially for this model, it is a dual pump carburetor now.
Allways happy travels and happy Airstreaming, once i a able to post some pictures (sorry Peter, you explained it to me, but i am a computer dinosaur!), i will show my beauty here in Germany !
If anybody is on the forum from Germany, or at least from west europe, let me know, we could share some expiriences!!!!!
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Old 07-17-2015, 03:25 PM   #21
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1997 30' Excella
1983 31' Airstream310
Austin , Texas
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Originally Posted by Roquefort View Post
One last question:
If i decide to install a new or maybe used TBI intake kit, is my BANKS system still "up to date"? I bought it exspecially for this model, it is a dual pump carburetor now.
Marcus,Your Banks system would only improve any Electronic Fuel Injection, in my opinion.

1983 310 Classic Motorhome
1997 30' Excella Trailer
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