Diesel Engine Designs

Good article... been aound for a while, but cannot really comment as I have... ooooh two 6/71's onboard... and may be seen as having a preference.....:D

Seriously though .. you need some serious space for a DD two stroke and absolutely no good if you need something light weight, just simply forget it!!!! Ours rated at approx 385 HP each comes in dry at 1490 Kg each !!
 
good read,although as you say, a bit dated, but still true today, highly strung diesels do have a tendency to "let go early" I for one, believe it is due to the over ambitious servicing schedules the manufacturers impose on these lightweight high output units, I'm relating to car and small truck units, my knowledge of boat engines isn't great, but they are not unrelated to each other
 
Divemaster1 said:
Good article... been aound for a while, but cannot really comment as I have... ooooh two 6/71's onboard... and may be seen as having a preference.....:D

Seriously though .. you need some serious space for a DD two stroke and absolutely no good if you need something light weight, just simply forget it!!!! Ours rated at approx 385 HP each comes in dry at 1490 Kg each !!
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ANd spares dropping off the back of almost all the oil rigs which use them in the cranes and elsewhere.....Lovely sound starting up:)
 
Marsupial said:
I found this today and had a read, I found it very interesting so I thought some of you might like it even though its over 10 years old.

http://www.yachtsurvey.com/comparing_diesel_types.htm
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David Pascoe's site has indeed been around for many years but it's still worth a read because he talks a lot of sense, particularly this article about high powered diesels. IMHO, he is absolutely correct in what he says about the longevity of high powered diesel engines. Many marine engines are marinised versions of engines found in cars, trucks and industrial applications like construction machinery but in these applications, the engines are usually rated to a much lower max power. This is because these applications require the engine to be reliable over a much higher number of operating hours than a boat. A typical pleasure boat does 100 hours per year or less; that's equivalent to only 3-4000 miles per year in a car. Furthermore, because most boats, particularly planing boats. are marketed on speed (every planing boat has to achieve at least 30kts these days), boat designers need the highest possible power they can get out of the lightest engine they can find. Engine manufacturers have responded by squeezing ever more power out of increasingly lighter weight engines. That's fine because material and combustion technology has advanced but whether the technology has advanced at the same rate as horsepower is a moot point. Pascoe is quite right. More power and more rpm means more heat and more heat means more wear. Today's high revving high power marine turbo diesel engines are very different from the old plodders on which the reputation of diesel engine longevity was built.
Now we come to another problem. Ever tighter emissions regulations require engine manufacturers to control engine fuelling more accurately. In my business (construction machinery) we use many of the same types of diesel engines found in boats (eg Cummins, Volvo, Cat) and we are finding an increasing trend of premature engine failures. Furthermore, we are also finding that the latest engines are noisier, mainly because the cooling fans seem to work harder. We have been told that in order to meet tighter emissions regulations, engines have to run leaner and because there's less excess fuel to provide a cooling effect, modern engines run hotter than before and increased heat means increased wear.
I would not be surprised if the same thing happened with marine engines. More power, lighter weight, more heat, reduced wear life
 
Deleted User said:
We have been told that in order to meet tighter emissions regulations, engines have to run leaner and because there's less excess fuel to provide a cooling effect, modern engines run hotter than before and increased heat means increased wear.
I would not be surprised if the same thing happened with marine engines. More power, lighter weight, more heat, reduced wear life
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That's a weird explanation they gave you.
If that's a well known effect, why not simply design a more "powerful" cooling system? Which in boats is even easier than in many other applications, btw.
 
Er, as I said the cooling fan works longer (and noisier). Obviously there are no cooling fans on marinised engines so I guess the engine manufacturers do uprate the raw water cooling systems accordingly. But uprating cooling systems means extra cost, extra weight and bigger dimensions. The main problem as I understand is that the emission regulations (Tiers 1,2,3,4 etc) are changing faster than the engine manufacturers can redesign their engines and amortise the costs. Some manufacturers are choosing to withdraw certain models from the market whilst others are doing belt and braces redesigns of existing models whilst at the same time trying to minimise the cost of the redesign because they know the regulations are changing in the next couple of years. We have had a number of Cummins failures recently and this story comes from one of their engineers
 
epervier said:
good read,although as you say, a bit dated, but still true today, highly strung diesels do have a tendency to "let go early" I for one, believe it is due to the over ambitious servicing schedules the manufacturers impose on these lightweight high output units, I'm relating to car and small truck units, my knowledge of boat engines isn't great, but they are not unrelated to each other
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So what life span do you give to Volvo's new 2.4l D3 pushing out 220hp? That's not far off the once sacred 100hp/l that you used to see in high performance petrol road cars! IMO, I think Pascoe might have a few choice words to say about its likely longevity :)
 
Deleted User said:
Now we come to another problem. Ever tighter emissions regulations require engine manufacturers to control engine fuelling more accurately. In my business (construction machinery) we use many of the same types of diesel engines found in boats (eg Cummins, Volvo, Cat) and we are finding an increasing trend of premature engine failures. Furthermore, we are also finding that the latest engines are noisier, mainly because the cooling fans seem to work harder. We have been told that in order to meet tighter emissions regulations, engines have to run leaner and because there's less excess fuel to provide a cooling effect, modern engines run hotter than before and increased heat means increased wear.
I would not be surprised if the same thing happened with marine engines. More power, lighter weight, more heat, reduced wear life
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Certainly Pascoe has put into words my own experience of diesel engines but I have no experience of the DD. The point you raise about emission regs is very pertinent. My own thoughts are that to meet the regulations the fuel has be completely combusted and although this leads to greater efficiency it could also lead to localised hot spots in various parts of the engine. These will cause castings to distort which will lead to premature failure. Just beefing up the cooling system wont necessarily overcome this problem .
 
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AdeOlly said:
So what life span do you give to Volvo's new 2.4l D3 pushing out 220hp? That's not far off the once sacred 100hp/l that you used to see in high performance petrol road cars! IMO, I think Pascoe might have a few choice words to say about its likely longevity :)
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Who knows but 220hp is a lot from 2.4litres but it will be the 3rd or 4th owner of the boat who finds out just how reliable they are. I guess the D3 is a relative of the D5 car engine which has about 175hp max(?)
 
Deleted User said:
Who knows but 220hp is a lot from 2.4litres but it will be the 3rd or 4th owner of the boat who finds out just how reliable they are. I guess the D3 is a relative of the D5 car engine which has about 175hp max(?)
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Volvo sell the 2.4 engine @ 140 hp

for 'sporty' Volvo drivers they sell the same engine as the D5 185 hp

You can pay £640 notes to a Volvo main dealer to have a Volvo approved software upgrade to increase the D5 to 205hp and remain in warranty.

So next time you get burnt off at the lights in a puff of diesel smoke by a flat capped grey haired Volvo driver you know the score ;)
 
DAKA said:
Volvo sell the 2.4 engine @ 140 hp

for 'sporty' Volvo drivers they sell the same engine as the D5 185 hp

You can pay £640 notes to a Volvo main dealer to have a Volvo approved software upgrade to increase the D5 to 205hp and remain in warranty.

So next time you get burnt off at the lights in a puff of diesel smoke by a flat capped grey haired Volvo driver you know the score ;)
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Ha ha, I know exactly how V70's drive as I bought my SWMBO a T5 version some years ago. The only puff you get from a high powered V70 under acceleration is the puffs of smoke from the rubber as the front tyres light up scrabbling for grip whilst the car goes nowhere.
 
2.5liters turbodiesel on 250hk have FNM (HPE 250)
had quite a long time so 220hk should not be a problem for the volvo!

Otherwise it is incorrect to say that new diesel engines run leaner. Lean means high air excess and that which is typical of today's diesel engines are small air exsess. There is therefore many uses common rail to avoid smoke at low lambda!

Volvo V70 with 200hp is terrible to drive! No traction! Hi fuel consumption also! The diesel i dont know!
 
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