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barrysnowball

fuel consumption

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If I had 2 narrowboats which in all other respects were the same, but one had an old low revving thumper, and the other had a modern high revving growler, which would have the better fuel economy?

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Neither

 

They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine

 

Richard

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Neither

 

They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine

 

Richard

Ours routinely averages 1.6l/hr at modest speed. (Beta 43 with 3 alternators)

 

So I think that slow revving (less friction) under-alternatored engines are quite a bit more economical.

 

Also, a smaller engine working reasonably hard is more economical than a larger engine working less hard but producing the same power

Edited by nicknorman

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Neither

 

They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine

 

Richard

Mine has a BMC 1.5 and although I've only put 70 hours on it since I bought it, dipping the tank with the gradiated dipstick suggests that it has used almost exactly 70 litres of diesel.

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You want a proper engine...

 

double-d-ex-london-double-decker-bus-auc

 

(Sorry for the image size, borrowed from a fave website of mine lol)

 

Lee.

 

E.T.A. - You don't want the gearbox though, semi-auto Voith, utter utter pants!

Edited by Black Country Lee

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a modern common rail engine might be 10% better in diesel drinking, but a good or bad propeller might be a difference of 20% or more.

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Ours routinely averages 1.6l/hr at modest speed. (Beta 43 with 3 alternators)

 

So I think that slow revving (less friction) under-alternatored engines are quite a bit more economical.

 

Also, a smaller engine working reasonably hard is more economical than a larger engine working less hard but producing the same power

 

But what of slow revving over alternatored engines rolleyes.gif - higher fuel consumption but electrical bliss wink.png

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You want a proper engine...

 

double-d-ex-london-double-decker-bus-auc

 

(Sorry for the image size, borrowed from a fave website of mine lol)

 

Lee.

 

E.T.A. - You don't want the gearbox though, semi-auto Voith, utter utter pants!

I have seen several boats fitted with old Gardner bus engines

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But what of slow revving over alternatored engines :rolleyes: - higher fuel consumption but electrical bliss ;)

No - the alternators go too slowly to do anything useful!

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I have seen several boats fitted with old Gardner bus engines

 

6LXB = Gardner 180 - hmm!

 

yebbut, yebbut, yebbut, its not in a boat.

 

 

fishing vessel or thames tugboat yes., absolutely.

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A bigger prop is to some degree more efficient than a smaller, faster turning one - but then a boat able to turn a bigger prop may need to have a greater draught, which will create more drag (or need to travel more slowly) on shallow waterways, so there's an element of 'swings and roundabouts' on that one.

 

Tim

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Thanks for all the useful comments. In answer to "Which do I want", it is most certainly on old thumper. I love working on engines, and they were so beautifully engineered. I'm glad that fuel costs is no longer a deciding factor.

All I have to do now is find the right boat. The searching will be as pleasant as the buying.

Thanks again for all your replies.

Barry.

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A bigger prop is to some degree more efficient than a smaller, faster turning one - but then a boat able to turn a bigger prop may need to have a greater draught, which will create more drag (or need to travel more slowly) on shallow waterways, so there's an element of 'swings and roundabouts' on that one.

 

Tim

That's correct, but using the largest possible within its limitation of the boat and practicality, and pick a gear ratio to give an optimal propeller size/rpm to suit. and use a efficient designed propeller.

 

but there is also different efficient designs with the same diameter/pitch and different layout of the swim that change the inflow to the propeller

 

if a modern engine is 10 % more efficient then an older, but use a 20% less efficient propeller, the result is that the older one seems to be more efficient.

Edited by Dalslandia

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Honestly, at first glance at the pic. I thought someone had fitted that into the boot of a trabant or something, its a bus innit, seriously though, there will not be a vast difference, to shift, say 20 tons at 4 mph requires x calories / kilowatts of diesel burnt and so long as rhe engines are not extreme examples the fuel used will be similar., (I failed o level physics by the way so please don't shout)

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45 foot NB, Lister LPWS4, 3:1 Hydraulic gear box, 1800 rpm gives 3-4 mph = 2.1 litres per hour

make sense.

 

saw someone doing 2.8 mph average, and using 1 liter or so.

 

3-4 mph is 3.5?

 

3,5/2,8=1,25 ^3 = 1,95 liter/h

 

most diesel engines use the same amount of fuel per HP, it just need some amount of fuel to run

the speed of the boat have big influence on power and fuel needed V ^3 (or^2.8)

Edited by Dalslandia

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