Diesel engine HP output

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nevillenolan

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Can anyone explain why some diesel engine manufacturers have models with different maximum horsepower figures - but it's the same block?

Nanni's 2.45 and 2.5 both use the Kubota Z482 - but produce 10HP and 14HP.

Same bore and stroke, same maximum revs, but two different outputs.

Sole/Mitsubishi does the same thing.

How do they do it - and why wouldn't you want the larger horsepower rating?


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with same block, bore and stroke the only things wd be a different piston (higher compression) and bigger injectors/fuel flow. But with same block twd be best to have the lightly stressed unit praps for longer life?

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Thanks.

Compression's the same - so I suppose it can only be the injectors.

Apart from the fuel saving and perhaps a longer lasting engine, are there other reasons to go for the lower HP?

Would more HP be harder to handle in low speed manouvering? And if 10HP will do, would a 14HP unit that rarely does any work glaze over and smoke?

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ooer, engines are loads more complicated than that. It can easily happen that higher powered engines are actually more efficient (mpg) than smaller ones at the same output. Sure, the bigger engine will use more fuel but then it'll get you there faster.

As for glazing, if you are gonna glaze a 14hp then the4 10hp would glaze as well. You have to work quite hard to glaze bores these days.

Otherwise, usually yes imho - more power is less useful at lower speeds for manoevering. But the difference wd be noticeable say between 8 and 15 hp - whereas 10-14 is a bit marginal.

Ask the supplier for their experience. Whcih is more reliable? Which wd they buy?

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<quote>
Ask the supplier for their experience. Whcih is more reliable? Which wd they buy?
</quote>

Come on, they would say 'the most expensive one'
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<hr width=100% size=1>Thanks

Leyton
(EXTAR Solutions - Software that works for you)
 
Thanks for your help.

I assume then that Volvo's 2010 is slightly less powerful than the (very similar cubic capacity) Kubota-based engines because Volvo has been more conservative in its injector settings, for longer life. Or am I being generous?

Beta, Nanni and others are quoting 10.5-14hp figures, where Volvo's quoted max is 10. The Kubotas are very slightly lighter too.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by nevillenolan on 26/04/2004 15:17 (server time).</FONT></P>
 
Hi,
One point not covered so far is that whilst a diesel engine may be rated at say 40 hp, it will not use the max fuel for that rating (which is approximately 1 gph for every 20hp developed), unless it is loaded to that effect.

In other words if it is not developing the power because it is not being loaded, it wont use loads of fuel. A diesel burns the amount of fuel for the output power being drawn off it. Full throttle, max revs and load, maximum fuel use. Because of the way propellors work if you cut from 100% revs to 80% you may reduce fuel consumption by 40%.

Good hunting. Paul

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Sorry, could not help it - Just had tube stack in heat Exchanger go belly up!
got fixed now but what a pain!! had to get bowman to make me 1



<hr width=100% size=1>Thanks

Leyton
(EXTAR Solutions - Software that works for you)
 
Another angle on this is that a user 'the customer', may have in his mind he wants say 20hp, another wants 15hp and another only 12hp. It is cheaper, and more profitable for any manufacturer to have as many common parts as possible, this ultimately, also keeps cost down for the customer.With a common block for example, the manufacturer then just needs to set fuel pumps and injectors accordingly and is still able to have happier customers. This is commercial sense all round, but most engines like ALL boats are a compromise, price, weight, power, etc.

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..but also power output effected by cam shaft lift and duration, valve diameter, fule injection timing, port size and shape, fuel temp, engine temp, compression not only controlled by piston height but also by head gasket thickness....and so it goes on, I think largely in cases such as the 10 hp vs 14hp case then yes its mainly done by fuel.....not sure if this post added anything or was just splitting hairs....

<hr width=100% size=1>Rehab is for quitters.
 
Re: micro-splitting and ....

Agree with everything you say except the compression ratio is what matters regardless whether it is done by piston height, skimming the head or gasket thickness (assuming the combustion shape is as efficient and for the effect we are talking here it will do).

What no-one has mentioned in the whole thread (not that it applies to 10 -14 hp motors but the principle applies) is turbo boost pressure and intercooling. More boost = more air/oxygen in for the same nominal compression ratio and intercooling condenses the air adding to the effect and more than overcoming the heating effect of the turbo. In fact some "higher tuned" engines have a lower nominal compression ratio because so much extra gets in and it might explode with a non-turbo comp ratio.

As for different power for the same capacity, remember Volvo 6 series engines started with 155 HP and ended up with 306 HP many years later but the same capacity and same block.

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Apart from what others have said here, different companies measure HP in different ways, some at the prop, some at the crank. Taking into consideration transmission losses, it can make a big difference.

<hr width=100% size=1><A target="_blank" HREF=http://www.arweb.co.uk/argallery/colspics> Cols Picture Album</A>
 
So does that mean at various times of the year you have no HP at all if measured at the prop?

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captain.gif
 
Re: micro-splitting and ....

Absolutely Duncan, but it is chicken AND egg. You can't just turn up the fuel supply, well you can on a "down-rated" engine, but at some stage you need to get extra air/oxygen in. Then you are right you need to increase the fuel supply but the original poster just wondered about different HP for the same swept capacity so I pointed out how it can be/is done

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