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Old 07-30-2020, 01:21 AM   #1
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Short Bus & engine/gearbox replacements

Hi - as a total newbie, I'm starting out on my search for the right skoolie to convert. The mpg attained by some is a big frightener for us in UK. We have diesel at around £1.20 a litre, so that's approx US$5.90 for a US gallon. I think your average is US$2.43 a US gallon, so we're over double that.

With that in mind, I'll probably be looking for one of the shorter 'mid sized' skoolies to give me 20 to 25 feet of living space to play with. These seem to come with DT466 diesel engines which, although robust, drink fuel....

So, this takes me to my big question: has anyone changed out the original engine/gearbox to something more economical? Key factors are that this would need comparable engine BHP and torque. I've looked at Ford F150 powertrain options as a starter:

Ford F-150 Engines:

3.3-Liter Ti-VCT V-6: 290 hp, 265 lb-ft
2.7-Liter EcoBoost V-6: 325 hp, 400 lb-ft
3.5-Liter EcoBoost V-6: 375 hp, 470 lb-ft
High-Output 3.5-Liter EcoBoost V-6: 450 hp, 510 lb-ft
3.0-Liter Power Stroke Turbo Diesel V-6: 250 hp, 440 lb-ft
5.0-Liter Ti-VCT V-8: 395 hp, 400 lb-ft

For us Brits and driving in mainland Europe, the diesel option is preferable, however it looks a little light at 250hp although torque seems good.

Look forward to any comments!
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Old 07-30-2020, 01:53 AM   #2
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The Sprinter vans with 3.0 turbo diesel get about 15mpg. Can't get much better than that.
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Old 07-30-2020, 02:03 AM   #3
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the other direction

I am going older mechanical injection diesel. I expect minimum 12-14 miles to the gallon... and I think I can get 18 MPG.

cummins 12valve 5.9 with 6 speed manual transmission.... how ever

there are several diesels that europe has .... we dont get in the united states.

I have not seen any discussion of new diesels in older busses. I am seeing, I think, more gasoline engines in busses.

william
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Old 07-30-2020, 02:05 AM   #4
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Is that a Mercedes Sprinter? Or a different type of Sprinter?

In UK we have 3.0 V6 Turbo Diesel Sprinters (Merc) and they are quoted as around 28mpg (Imperial gallon) 'real life'. I guess that's a mixture of laden and unladen. I have seen US website stating 14.8mpg, US gallon.

Imperial (UK) gallon is 20% more than US gallon...
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Old 07-30-2020, 02:09 AM   #5
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Six speed transmission might allow for longer leg-room in the gears so better on motorway (freeway), unless it's a close ratio box?

Older systems wouldn't have ECU and the ton of interlocks to frig/defeat or reprogram, so a benefit there vs. better mpg with newer engines.
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Old 07-30-2020, 09:26 AM   #6
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Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
six speed

The box in question is an NV5600.... 6th is .73 and 5th is direct

I chose this transmission because I liked the gear spacing... progressive spacing. The lower gears are a little farther apart and get closer as you go up through the gears.

IF my math is correct 1875 rpm in 6th gear at 65 mph -104kph

and if I have to down shift 2525 rpm in 5th gear at 65 mph - 104 kph

The bus will not have stuff stickin out into the air stream, trying to keep the outside as smooth as I can and will have undertrays.

Total weight to be 12,000 lbs 5,400 Kg

Design cruise speed is 65 mph

william
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Old 07-30-2020, 09:29 AM   #7
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benz 300sd

I wonder what can be done with the older mercedes 5 cylinder inline out of the cars.... seemed to be pretty durable engine.

fault tolerant is how I think of the mechanical set ups. another advantage to mechanical injection.

with electrical system failure and manual transmission it will still go.....

william
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Old 07-30-2020, 10:21 AM   #8
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Thanks for the info. I guess that transmission wasn't a standard offering in any of the production skoolies? A Google search paired it with a Cummins 5.9 Litre engine in Dodge 2500 and 3500 series trucks. Wiki lists it as 'close ratio'.
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Old 07-30-2020, 04:45 PM   #9
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Quote:
Originally Posted by magnakansas View Post
I wonder what can be done with the older mercedes 5 cylinder inline out of the cars.... seemed to be pretty durable engine.

fault tolerant is how I think of the mechanical set ups. another advantage to mechanical injection.

with electrical system failure and manual transmission it will still go.....

william

In stock form the 5 cylinder 617A Mercedes is 125hp. Do not remember torque values. The injection pumps can be turned up for more fuel, enlarging the pre chamber spray holes helps a lot, and setting the boost control up around 15-16 psi, will really wake the 617a up. I have also messed with the 616 4 cylinders and added turbo, and other mods. Fun little engine to play with.

I would say the 617a (the "a" designates turbo) would be ok in a van cutaway.
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Old 07-31-2020, 04:53 AM   #10
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125 HP seems a little light to me, and I guess associated torque might also be a struggle?
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Old 07-31-2020, 09:33 AM   #11
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Magnakansas. I hope you're planning to put that NV5600 in a short bus, and keep your GVW down, and drive like your on ice every day.

I've hauled a 10,000lb trailer with a dodge that had the NV.
Not my truck but with 90K miles on the clock second gear syncro was so shot you couldn't get into second without rev matching, and third was on it's way out next.

I haven't heard good things about that trans in a heavy duty application. I would not expect it to last long hauling around 12,000lb all the time.

If you're real smooth on the stick and go easy on it im sure it could, driver technique is a big factor on the longevity of a manual trans.

Just wanted to caution you after my experience with the thing.
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Old 07-31-2020, 09:36 AM   #12
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As for O.P.

Have you considered a CNG conversion, or CNG supplement fuel? if diesel is so expensive whats the prices for your CNG in the UK?

I know you guys have the safety nazi's over there too, will you even be able to do a DIY CNG conversion to a road legal vehicle?

I was going to do it on my bus, even bought the tank and all the parts, as it would bring my cost per mile down about 50%, and I could keep the existing powerplant in the bus.
When diesel prices cratered ( as low as 1.27 a gallon ) I just couldn't justify switching to the CNG any more.
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Old 07-31-2020, 11:34 AM   #13
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A key to better mpg is having a small frontal area. You might notice all those 'popup' features on various campers. Those big two-story tiny houses they make are absolutely the worst, it is like they are trying as hard as possible to make them get so bad of MPG when towing that you will never actually move one.

I'd like to build a bus with a Roof Drop. So you can raise it back up with parked.



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Old 08-01-2020, 11:51 PM   #14
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CNG (and LPG) conversions

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Originally Posted by Jsneeb View Post
As for O.P.

Have you considered a CNG conversion, or CNG supplement fuel? if diesel is so expensive whats the prices for your CNG in the UK?

I know you guys have the safety nazi's over there too, will you even be able to do a DIY CNG conversion to a road legal vehicle?

I was going to do it on my bus, even bought the tank and all the parts, as it would bring my cost per mile down about 50%, and I could keep the existing powerplant in the bus.
When diesel prices cratered ( as low as 1.27 a gallon ) I just couldn't justify switching to the CNG any more.
I've seen a fair few LPG pumps at fuel stations, but not noticed CNG option. Then again, I've not been paticulalry looking.

Reading up, here's a great link summarising benefit/risk for LPG conversions. It covers both car and bus/lorry:

https://www.honestjohn.co.uk/faq/lpg-and-cng/

The 27th July UK price for LNG was £0.64 per litre (US$0.83) which is roughly half that of diesel.

Tracking down CNG price was quite difficult! Ok, it's sold in kg rather than litres, conversion being that 1kg CNG = 1.5 litres CNG. It looks like around £0.61 per litre equivalent, making it similar to LPG costs.

Here's a link comparing CNG and LPG:

https://www.diffen.com/difference/CNG_vs_LPG

With pump prices similar, the main factors would be:
- safety of installation: CNG is at high pressure;
- availability of fuel: LPG more available than CNG
- cost of conversion: not looked into it much, but figure CNG would be more due to high pressures involved.

The point raised about aerodynamics is fundamental: driving a brick through static air is not the best place to start. The pop-up or add-on air deflectors make a significant difference for minor outlay.

There a whole lot of research and possibilities. One thing's for sure, DIY interior is one thing, DIY CNG or LPG conversion looks like not a good idea.
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