the size of my engine

[dor]

Yes it's brake horse power. The Lister JP2 is 21 brake horsepower (18 for very early ones), they are the same horses as Beta etc quote.

 

Thanks Tim. I always wonder this when I see HP ratings given for engines from the early 50s or before. (And you can get about 50BHP out of a 750 cc Austin 7 engine...)_

[George94]

Can't comment on boats, but until recently I had a 1600, single carb, flat 4 air-cooled engine in my camper. It had about 40BHP. I replaced it with a 1955cc, longer stroke, bigger bore, twin carbed engine with about 90bhp. I now drive it slightly faster and accelerate faster (because I can). The old engine was foot to the floor, as it was underpowered for the van when trying to keep up with modern traffic, the new one barely needs any pedal to cruise. They both return exactly the same 28mpg (brimming the tank calculation).

 

Edit to add: Same gearbox.

 

You've got a more modern, more efficient, engine.

 

If the same engine is available in different sizes, the smallest will be the most economical (assuming it is not totally over-loaded).

[Athy]

Well, that's true to an extent, but all else being equal, a bigger engine will use more fuel. It can't be otherwise.

George, that is an interesting comment. Now, let me say that (in case you hadn't noticed) I am devoutly non-technical. But recently somebody much more mechanically minded than me told me that older engines such as my Gardner use LESS diesel than most modern engines. His reasoning, as I understood it, was that instead of pushing four pistons up and down lots of times per minute, the Gardner (1,700 rpm flat out) was pushing two pistons up and down half as many times per minute.

Even I could see that the bigger piston size in a 2,800 cc 2-cylinder engine might make a difference to fuel consumption - but had the chap perhaps got a point?

[Albion]

You've got a more modern, more efficient, engine.

 

If the same engine is available in different sizes, the smallest will be the most economical (assuming it is not totally over-loaded).

Not in the case of vehicles I'm afraid. If you are having to flatten the throttle to the floor to make reasonable progress with the smaller engine but the larger engine can pull the vehicle easily you can quite often achieve a better economy with the larger engine because you're not working it as hard. Back in the late 70s, when there was another recession and emphasis on vehicle economy, Ford (my employer at the time) introduced a weight reduced, budget, economy version of the Escort. It was never as economical as the standard model because people had to push it harder to maintain comparable speed to the traffic flow. Needless to say people soon didn't want the budget version and it soon had options to add back in the carpets and trimmed door panels instead of rubber mats and cardboard panels. Soon after that it was dropped.

Roger

[boathunter]

You've got a more modern, more efficient, engine.

 

If the same engine is available in different sizes, the smallest will be the most economical (assuming it is not totally over-loaded).

It's ceratinly not modern, it's a 60 year old design. So is the new one.

 

It's the same basic engine as before, same crankcase, same heads, same valve sizes, same rockers, same con-rods, same push-rods, slighly different cam, longer throw crank (76mm compared to 69mm), bigger bore (90.5mm compared to same 86mm). Same exhaust system. The twin carbs have helped too.

 

I was expecting less mpg which is why I checked. Same journey too for what it's worth. Maybe the wind was blowing in the opposite direction - it's shaped like a loaf of bread.

Edited November 11, 2012 by boathunter

[GUMPY]

You should try the 411/412 engine thats what my daughter has in her 64 Samba.

Not the most economical of busses but it is quick

[bowten]

It's ceratinly not modern, it's a 60 year old design. So is the new one.

 

It's the same basic engine as before, same crankcase, same heads, same valve sizes, same rockers, same con-rods, same push-rods, slighly different cam, longer throw crank (76mm compared to 69mm), bigger bore (90.5mm compared to same 86mm). Same exhaust system. The twin carbs have helped too.

 

I was expecting less mpg which is why I checked. Same journey too for what it's worth. Maybe the wind was blowing in the opposite direction - it's shaped like a loaf of bread.

Yea I had the 1900cc engine in a VW van and added a Holley 2 barrel I acquired from the States,went like stink and was more economical.Must have been far more efficient.

Edited November 11, 2012 by bowten

[Tony Brooks]

Well, that's true to an extent, but all else being equal, a bigger engine will use more fuel. It can't be otherwise. If it were, we'd all have gigantic engines, and use hardly any fuel at all.

 

 

No it is not. The specific fuel consumption typically falls through the first part of the rev range and then as intake tract throttling and exhaust back pressure rises it increases. A large engine operating at its best specific fuel consumption would be more economical that a small one operating above it given they were both driving the same boat and in the same conditions.

 

And yes, Renault at one time fitted a large well tuned twin choke carb engines into their economy R5 but limited the throttle opening.

 

It takes X hp to undertake a specific task and the engine that produces that at the point of its best fuel consumption will use the least fuel. This is borne out by typical average canal boat fuel consumptions of just over a litre and hour however large or otherwise the engine is.

[bizzard]

Yea I had the 1900cc engine in a VW van and added a Holley 2 barrel I acquired from the States,went like stink and was more economical.Must have been far more efficient.

That engine went into the larger 1970's VW Variant estate, the one with the petrol fired cab heater.

[bowten]

That engine went into the larger 1970's VW Variant estate, the one with the petrol fired cab heater.

Indeedee!

[Pentargon]

Not really, you're talking about an old low-revving and relatively high torque engine, while the OP was talking about a modern Beta where 25hp is not nearly enough. I'd love to see you coming downstram on the tidal Thames and try to turn a 70ft narrowboat into Limehouse on a strong ebb tide with that.And why would you imagine I know anything about your boating experience Mike? I don't pay any attention to claims made by people I don't know on the internet.

 

Blackrose: In one statement I have sussed how much you have to learn about The River. And so I'm sure has Mike the Boilerman who is a well proper Riverman: I know by the way he talks and what he says that he is a Riverman. And I am well pleased you do not pay any attention to claims made by people you don't know on the internet. Can you include me in that catagory and oblige?

[George94]

Sorry chaps, but if you are right, why aren't you all fitting 24 litre engines?

 

I did say "all else being equal". You can't compare engines with totally different carburettor systems, nor can you compare engines where one is being asked to perform outside its designed load parameters.

 

As for old-style engines being more economical, well, again, all is not equal. My JP3 may be big, but it's only 30hp. Yes, it's pretty economical at normal cruising speeds, but unlike a modern engine it's got nothing in reserve at high revs because it doesn't HAVE high revs. Old and new are chalk and cheese.

 

Nonetheless, what I said is certainly true for this type of engine. A JP4 would use more fuel.

 

What I was saying to the OP was that while a 35hp Beta or Kubota or whatever would be quite adequate, a larger engine of the same type (remember - all else being equal) would use more fuel.

 

A larger engine, all else being equal, will be heavier, and have a greater surface under friction. It must use more fuel.

[bizzard]

And me. Being a bit of a Fred Dibnah I can usually tell with practical matters anyhow whether or not someone has or has had long term genuine hands on experience with engines or whatever, or is just blagging their way through a discussion by Googling or has been searching these archives for the answers so as to make themselves seem clever. I find the Googling one upmanship very boring and don't usually parcipitate. MB is also known for his River-Dance routine i believe.

[RLWP]

<snip>

 

You can't compare engines with totally different carburettor systems,

 

<snip>

 

Huh???

 

Richard

[George94]

Huh???

 

Richard

 

I said that all else being equal, a larger engine will use more fuel than a smaller one.

[RLWP]

Carburettor?

 

Richard

[Paul C]

In general terms:

 

- The more cylinders, the more losses due to friction etc - the less economical

- Diesel engines tend to be most efficient at full power. Part load, efficiency drops

- Petrol engines at part load are even less efficient than the equivalent diesel at part load, because a petrol engine has a throttle, a diesel does not*

- The more modern the engine, the more efficient it is. But it would need additional technology to be more efficient, not just 'newer' of the same basic design. eg. a modern diesel with direct injection, ECU, turbo etc will be more efficient than an old diesel with mechanical fuel pump, no turbo. But a modern Beta engine doesn't have an ECU, turbo etc so doesn't gain anything over an older engine with the same features.

 

 

 

 

* Some very modern petrol engines don't have a throttle any more - in an attempt to improve their efficiency

[George94]

Carburettor?

 

Richard

 

Somebody was talking about his petrol engine in a camper.

 

Feel free to read the thread!

[RLWP]

Somebody was talking about his petrol engine in a camper.

 

Feel free to read the thread!

 

I see. Nothing to do with boat engines then

 

Richard

 

In general terms:

 

- The more cylinders, the more losses due to friction etc - the less economical

- Diesel engines tend to be most efficient at full power. Part load, efficiency drops

- Petrol engines at part load are even less efficient than the equivalent diesel at part load, because a petrol engine has a throttle, a diesel does not*

- The more modern the engine, the more efficient it is. But it would need additional technology to be more efficient, not just 'newer' of the same basic design. eg. a modern diesel with direct injection, ECU, turbo etc will be more efficient than an old diesel with mechanical fuel pump, no turbo. But a modern Beta engine doesn't have an ECU, turbo etc so doesn't gain anything over an older engine with the same features.

 

 

 

 

* Some very modern petrol engines don't have a throttle any more - in an attempt to improve their efficiency

 

I would say that was pretty close to being nonsense. I can see what you are trying to say, I think

 

Here's a clue - what does the throttle (that all petrol engines have) do?

 

Richard

[nb Innisfree]

We have an 1850cc LPWS4 with 40 bhp @ 3000rpm pushing a 60 nb, in deep water we can get almost 3000rpm but it just results in a small speed increase and a massive bow wave, total waste of fuel, but...it could be handy in an emergency on fast water if it made the difference between reaching a safe mooring or not.

 

I think the best compromise is a smaller engine with enough turbocharged power available to reach max hull speed for the few times extra power is neeeed.

[Paul C]

Using the valves to control air intake rather than a conventional butterfly throttle has the potential to create better swirl in the cylinder; and reduces pumping losses --> more efficiency. Also it improves throttle response.

[RLWP]

Using the valves to control air intake rather than a conventional butterfly throttle has the potential to create better swirl in the cylinder; and reduces pumping losses --> more efficiency. Also it improves throttle response.

 

Sorry - modern fuel injection systems still use a throttle body with a butterfly

 

What does it do to the engine?

 

Richard

[Paul C]

Sorry - modern fuel injection systems still use a throttle body with a butterfly

 

What does it do to the engine?

 

Richard

 

Have a look at BMW's Valvetronic and Fiat Multiair technologies.

[Albion]

Sorry - modern fuel injection systems still use a throttle body with a butterfly

 

What does it do to the engine?

 

Richard

Richard, as Paul C has said BMW have a system using controlled valve opening to throttle the engine in place of a conventional throttle body and plate. IIRC they started developing it when I was at Gaydon helping develop the Rover 75 and the Mini and that is quite a few years ago now. As he has said it reduces pumping losses and improves efficiency at the expense of greater complexity of course.

Roger

[Tony Brooks]

Sorry chaps, but if you are right, why aren't you all fitting 24 litre engines?

 

I did say "all else being equal". You can't compare engines with totally different carburettor systems, nor can you compare engines where one is being asked to perform outside its designed load parameters.

 

As for old-style engines being more economical, well, again, all is not equal. My JP3 may be big, but it's only 30hp. Yes, it's pretty economical at normal cruising speeds, but unlike a modern engine it's got nothing in reserve at high revs because it doesn't HAVE high revs. Old and new are chalk and cheese.

 

Nonetheless, what I said is certainly true for this type of engine. A JP4 would use more fuel.

 

What I was saying to the OP was that while a 35hp Beta or Kubota or whatever would be quite adequate, a larger engine of the same type (remember - all else being equal) would use more fuel.

 

A larger engine, all else being equal, will be heavier, and have a greater surface under friction. It must use more fuel.

 

Now will you answer my point about a larger (we are not talking silly number like 24 litres here, only the difference between 1.5 and (say) 2 litres) engine probably operating in a more economical part to its rev band. This is the CANAL WORLD forum and the OP asked about narrowboat engines.