jfm
Well-Known Member
100% agreed - if you're lucky or geeky enough to have water jacket heaters and Barring motors!
How Often Do You SDtart Your Motor.
- Thread starter ChrisB177
- Start date
100% agreed - if you're lucky or geeky enough to have water jacket heaters and Barring motors!
benjenbav
Well-Known Member
It's absolutely essential to run diesels up to temperature in the winter, preferably under load, even more preferably when not attached to the shore.....
....at least that's my story and I'm sticking to it.
....at least that's my story and I'm sticking to it.
A_8
Well-Known Member
I don't know about all your engines but it is stated in the manual for my KAD43's that they should be run up to operating temp every two weeks.
jfm
Well-Known Member
It's absolutely essential to run diesels up to temperature in the winter, preferably under load, even more preferably when not attached to the shore.....
....at least that's my story and I'm sticking to it.
Ah, of course, doh, you're dead right. Really needs a whole saturday. Weekly, when the weather's nice or the MiL is expected
jfm
Well-Known Member
Volvo manuals are devices intended to give VP as many excuses not to pay our under warranty as possible, so making the warranty program quasi discretionary. Another example is "reset valve clearances every X hours or every 12 months"
misterg
Well-Known Member
Noooo......
With respect jfm (and I have a lot of respect for you based on your contributions heareabouts....) I think you're doing the worst possible thing to your engines. So strongly do I feel this that I will attempt to explain why:
I don't know what engines you have in your boat (effin' big ones, I expect
) but they will almost certainly rely on hydrodynamic bearings for the major bearings in them (think crank journals, big ends, small ends, camshaft bearings, cam followers, etc.) These rely on a pressurised oil feed to keep the bearing surfaces apart. When the engine is stopped, most of the oil drains back to the sump and the bearing surfaces are left with a tiny amount of oil trapped between them. This oil film is so thin that the microscopic irregulatities on the bearing surfaces can 'catch' on each other if there is relative movement. When you start the engine from cold, the surfaces do indeed 'catch' on each other (in a microscopic way) and break off - wear - until the oil pump has had time to send cold, viscous oil all the way from the sump to each bearing.My first point? A disproportionate amount of wear occurs on start up, especially a cold start up (remember the Castrol GTX adverts?).
Next: Your cylinder block(s) are water cooled, and designed to run at a fairly constant temperature of ~100 deg C. The pistons moving inside the cylinder block aren't water cooled, but are still subject to the heat of the burning diesel. They will therefore run much hotter than the cylinder block. There is an optimum clearance between the piston, its rings and the cylinder wall for a good seal. Everything is machined to achieve this clearance taking into account the different tempertatures. In a cold engine (where everything is the same temperature) the pistons will be a relatively sloppy fit in the cylinder bores and so the rings won't seal as well. If you have cast iron blocks and aluminium pistons, they will be a really sloppy fit when cold, because they are machined to allow for the difference in expansion between cast iron and aluminium, too.
Point 2: There is more leakage past the pistons in a cold engine.
Point 3: Burning diesel creates water (chemistry).
The diesel that's injected into the engine ends up as 'products of combustion' - Mostly water vapour and CO2, but also SO2, etc. Some of this finds its way past the pistons and into the internal spaces of the engine (blow by). This happens to a greater or lesser extent at all times. If the metalwork of the engine and oil are hot, the water stays as a vapour and is vented by the normal means. In a cold engine, not only is there a greater than normal amount of blow by, there is also cold metalwork where the water vapour can condense and accumulate in the oil. SO2 and other nasties in the 'products of combustion' dissolve in the condensed water and find their way into the oil, too, eventually making it acidic.
Point 4: Water and acidic products of combustion will build up in the oil unless the oil is got hot enough for long enough to drive them off.
The contaminants in the oil are sufficiently aggressive to attack the white metal surfaces of the hydrodynamic bearings (you know, all the important ones!) in the engine. This attack proceeds regardless of whether the engine is running.
Point 5: Water etc. in the oil is a Bad Thing.
Summary:
Wear on startup is inevitable.
If the engine is started, but not brought to operating temperature for a period of time, water and other contaminants will accumulate in the oil which will attack the bearings.
Conclusion:
Start it up as little as necessary. When you do start it, get it good and hot before stopping it again.
I don't know why people (myself included) feel the need to run things 'just in case' and I can't see any logical reason for it. I think it would be 'kindest' to your engines to switch them off after a good run and leave them off for 6 months rather than running them for an hour a month. If I were to be slightly provocative, I would argue that visiting them once a month and tipping half a cup of water into the oil and walking away again would be kinder than starting them and running them for 1 minute - but I'm not provocative
Happy to debate any points, but it's the 2nd time I've typed this out (pressed the 'back' button last time and lost the lot
)Andy
hlb
RIP
So to recap, start engines only when necesary, it's the starting that does the damage. the oil is designed to stick on stuff for a long time. So once started, go a long way and get rid of the **** you induced starting it. The engine will wear out eventually, why wear it out quicker with more cold starts.??
MapisM
Well-Known Member
Very interesting post, thanks. Just a couple of questions:
1) When talking of leaving engines off for 6 months, do you mean if properly winterized I suppose? Leaving salt water sitting around the raw water circuit and exhausts for 6 months, without sealing filters and exhausts, that isn't a good idea in my books.
2) what do you think of the practice of cranking high perrformance gasoline engines every month or so, just for a second and without turning them on (that is, with the safety switch open), in order not to leave the same valve springs compressed? I've been recommended to do that even with the engine fogged and winterised.
misterg
Well-Known Member
I'm not making any comment on on the cooling side. It sounds like winterising is a good idea, but I don't know - If the raw water system is designed to hold salt water, why not leave it there?
If it's a manufacturer's recommendation, then go with it, but to me it sounds horrific from the engine's point of view. Every time you do this, you will lose a bit more of the tiny amount of residual oil in the bearings.
I really can't see that the valve springs of a high performance engine would be affected by leaving them compressed - Do you jack your high performance car up to stop the suspension springs being compressed? (OK, I know valve springs will be more highly stressed, but why should they be affected?)
It would have to be recommended and explained to me by somebody really credible for me believe that this did any good.
Edit: There are good reasons for turning big engines over occasionally, but I suspect this is done very slowly, and maybe with an externally pressurised oil supply. If you want to minimise the oil loss turn the engine "by hand" (by whatever means!)
Andy
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jfm
Well-Known Member
Noooo......
With respect jfm (and I have a lot of respect for you based on your contributions heareabouts....) I think you're doing the worst possible thing to your engines. So strongly do I feel this that I will attempt to explain why:
I don't know what engines you have in your boat (effin' big ones, I expect
My first point? A disproportionate amount of wear occurs on start up, especially a cold start up (remember the Castrol GTX adverts?).
Next: Your cylinder block(s) are water cooled, and designed to run at a fairly constant temperature of ~100 deg C. The pistons moving inside the cylinder block aren't water cooled, but are still subject to the heat of the burning diesel. They will therefore run much hotter than the cylinder block. There is an optimum clearance between the piston, its rings and the cylinder wall for a good seal. Everything is machined to achieve this clearance taking into account the different tempertatures. In a cold engine (where everything is the same temperature) the pistons will be a relatively sloppy fit in the cylinder bores and so the rings won't seal as well. If you have cast iron blocks and aluminium pistons, they will be a really sloppy fit when cold, because they are machined to allow for the difference in expansion between cast iron and aluminium, too.
Point 2: There is more leakage past the pistons in a cold engine.
Point 3: Burning diesel creates water (chemistry).
The diesel that's injected into the engine ends up as 'products of combustion' - Mostly water vapour and CO2, but also SO2, etc. Some of this finds its way past the pistons and into the internal spaces of the engine (blow by). This happens to a greater or lesser extent at all times. If the metalwork of the engine and oil are hot, the water stays as a vapour and is vented by the normal means. In a cold engine, not only is there a greater than normal amount of blow by, there is also cold metalwork where the water vapour can condense and accumulate in the oil. SO2 and other nasties in the 'products of combustion' dissolve in the condensed water and find their way into the oil, too, eventually making it acidic.
Point 4: Water and acidic products of combustion will build up in the oil unless the oil is got hot enough for long enough to drive them off.
The contaminants in the oil are sufficiently aggressive to attack the white metal surfaces of the hydrodynamic bearings (you know, all the important ones!) in the engine. This attack proceeds regardless of whether the engine is running.
Point 5: Water etc. in the oil is a Bad Thing.
Summary:
Wear on startup is inevitable.
If the engine is started, but not brought to operating temperature for a period of time, water and other contaminants will accumulate in the oil which will attack the bearings.
Conclusion:
Start it up as little as necessary. When you do start it, get it good and hot before stopping it again.
I don't know why people (myself included) feel the need to run things 'just in case' and I can't see any logical reason for it. I think it would be 'kindest' to your engines to switch them off after a good run and leave them off for 6 months rather than running them for an hour a month. If I were to be slightly provocative, I would argue that visiting them once a month and tipping half a cup of water into the oil and walking away again would be kinder than starting them and running them for 1 minute - but I'm not provocative
Happy to debate any points, but it's the 2nd time I've typed this out (pressed the 'back' button last time and lost the lot
Andy
Ah thnaks Anday - for a properly considered set of arguments. I see your point and agree all you say. In response
1. Agreed. Though this happens less with my 1 minute run than with other peoples 30mins. Of course it would happen even less if the engines weren't run at all -which is your point
Next: all agreed
2+3 Agreed
4 Agreed. But I'd like to calculate the amount of water in 1 minute of running, as a rough guess. Can't do that now, in airport terminal waiting for flight. might do later.
5 Yes, though the concentrations of water in my 50litre sump might be small (ref 4 above)
Summary I agree with you that it should be started as little as necessary. But the question of whether, when starting it, you should run it for 1 minute or half an hour is not clear cut, is it? It's a trade off maybe?. Running the engine till hot will get rid of the nasties that you mention. But it will also impose say 15minutes of quite cold running on the bearings etc, the badness of which you describe well. Now, if the amount of nasties is tiny, it's better not to worry about them and to save the 15mins of cold running. Whereas if the nasties are significant, it's better to eliminate them even though that imposes the 15mins of cold running. So it all comes down to the quantity of the nasties, right? And so it's not clear cut. Gotta go, flight called. Thnaks for the thoughts and info though. Will revert
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LittleShip
Well-Known Member
Noooo......
With respect jfm Blah Blah Blah ect
Andy
Seems you wasted your breath Andy ! I agree with you so lets you and I just keep knackering our engines.
Tom
old_salt
Well-Known Member
Hi Andy.
A super expiation it's all in there.
For me the best answer is as you say.
Edit: There are good reasons for turning big engines over occasionally, but I suspect this is done very slowly, and maybe with an externally pressurised oil supply. If you want to minimise the oil loss turn the engine "by hand" (by whatever means!)
To add to my previous post of how we did it in the Merch:-
For the bigger engined for us with TSDY's etc and providing there is the room to do it it would answer all the problems. I would think it is not beyond a reasonable workshop to make up the necessary bits oil pump, water heater/ cerk pump and rig a barring motor with a reduction gear box and belt drive it on to an exposed front end / shaft / pulley belt wheel or the hand start crank if you have one.
Us raggies don't have such a big problem most engines can be cranked over by hand with the decompresser a dozen or so turns and you have the oil run around and chances are you will let the all the mating bits come to rest in a different position.
My own boat's engine is an old Aluminium Air Cooled Enfield. I just decompress and wind it over by hand till the oil press comes up every so often.
A super expiation it's all in there.
For me the best answer is as you say.
Edit: There are good reasons for turning big engines over occasionally, but I suspect this is done very slowly, and maybe with an externally pressurised oil supply. If you want to minimise the oil loss turn the engine "by hand" (by whatever means!)
To add to my previous post of how we did it in the Merch:-
For the bigger engined for us with TSDY's etc and providing there is the room to do it it would answer all the problems. I would think it is not beyond a reasonable workshop to make up the necessary bits oil pump, water heater/ cerk pump and rig a barring motor with a reduction gear box and belt drive it on to an exposed front end / shaft / pulley belt wheel or the hand start crank if you have one.
Us raggies
don't have such a big problem most engines can be cranked over by hand with the decompresser a dozen or so turns and you have the oil run around and chances are you will let the all the mating bits come to rest in a different position. My own boat's engine is an old Aluminium Air Cooled Enfield. I just decompress and wind it over by hand till the oil press comes up every so often.
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MapisM
Well-Known Member
Well, aside from the fact that also salt water can freeze, just think of any AISI 316 s/s components (rails, passerelle, etc.), and you'll surely agree that even these are better off when rinsed with freshwater, rather than leaving salt drying on their surface... And many parts inside raw water system ain't 316 s/s!
Mmmm... I don't see why you can't. The characteristics of any spring (yes, including car suspensions) IS affected by both the number of compression cycles and duration, and this is a fact.
Now, whether it's worth to trade that off for the residual oil in the bearings, that's a good point. But bearing in mind that as I said we're talking about a winterised and FOGGED engine, I would expect that cranking the engine for an extremely short time will rather distribute than remove the oil.
I agree that it would be better to do that very slowly "by hand", though.
But it's almost impossible to do that, even with some sort of leverage, with a big block engine inside a small engine compartment.
MapisM
Well-Known Member
What gives you this impression?
Fwiw, I really appreciated Andy contribution even if I'm pointing out some other considerations.
And as I understand, also jfm who started from a very different viewpoint is now saying that he agrees with him.
misterg
Well-Known Member
I'm not quite done yet
(but I don't see it like that, anyway).Noooo.... (again
)I've not made it clear that the wear I highlighted as my first point above happens in the first few seconds of movement, not minutes - a little bit longer than it takes for your oil pressure light to go out.
It might help to explain a bit more about how hydrodynamic bearings work:
Your crankshaft journals, etc. don't run in the middle of their bearings.
When they're stopped, they rest wherever gravity or other forces (e.g. valve springs) take them. When they're running, they 'climb up' on a film of oil that's generated because the rotation of the journal 'drags' oil into the tapering clearance between the journal and the bearing. (The bearing only works because the journal is minutely off centre). Maybe this picture will make it clearer:
Contrary to popular wisdom, it's not the pressure from the oil pump that keeps the surfaces apart (that would be a hydrostatic bearing, and they do exist). All the oil pump has to do is get a surplus of oil to the wide part of the clearance between the bearing and the journal, and the relative movement does the rest. (Cams and their followers work the same way, btw.)
When an engine is started, there is no supply of oil to the bearing - all it has is what's stuck between the journal and the bearing, and the journal will be resting against the bearing with a few oil molecules in between. (The white circle in the picture above would be resting against the orange bit). As the journal turns, it drags what oil there is through the tapering gap between the journal and the bearing, pressurising it in the process and forcing the journal and the bearing apart with an oil film - the journal is 'climbing up' to its operating position. This takes time to happen. There's not as much oil as normal, so the film isn't as thick as normal, so some bits of bearing and journal make contact and break off (microscopically speaking) i.e. wear. Some of the oil from the pressurised film flows out sideways (like it normally does) and is lost from the bearing. It now has even less oil. Hopefully a big slug of fresh oil will arrive soon from the oil pump and allow the bearing to develop the full film thickness and *eliminate* this wear. If fresh oil doesn't arrive, the oil film in the bearing will get thinner and thinner. If you stop the engine at this point, some more of the oil film will leak away as the journal settles back to where gravity, etc. sends it so there will be even less oil there next time it moves.
Consider this in relation to point (1) in my original post, and also as an explanation of why I think 'blipping' engines over on the starter is a bad idea.
Edit (sorry, rushing before): jfm - the wear happens in seconds, so your 1 minute is no different to 1 hour or 1 day in that respect (there really is negligible wear in these bearings when they're run as designed with clean oil). It's a 'one off' event associated with turning over an engine with no oil pressure. /edit
Mapis - I'm sorry, but I don't know enough about the cooling side to comment further - it would seem to be engine specific.
Yes, of course valve springs are designed for particular stresses and fatigue life. I would personally be amazed if the cold creep rate for a compressed spring was anything more than zero. Maybe if someone is building dragsters where the expected engine life between rebuilds might just be minutes, I don't know.
Andy
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MapisM
Well-Known Member
Really useful reading - easily the best of recent times around here, thanks again.
I agree on everything, but...
A friend of mine builds steel springs of various sizes and for many different applications. And as I said, I know for sure that the number of compression cycles and duration affect the characteristics of any spring.
There are measurable differences in a spring like the ones used for engine valves after keeping it compressed for just one month!
Mind, instrumentally measurable of course, but you see what I mean.
Of course, you're correct when you imply that temperature can affect the creep rate even more, but also time alone can take its (however small) toll.
What I never considered is that the wear you describe can be relevant only upon blipping the engine, as you say.
Considering also that a consequence of accepting your viewpoint is that periodic winter trips to the boat aren't necessary anymore, I'm sold!
I agree on everything, but...
...trust me, you would be amazed in this respect.
A friend of mine builds steel springs of various sizes and for many different applications. And as I said, I know for sure that the number of compression cycles and duration affect the characteristics of any spring.
There are measurable differences in a spring like the ones used for engine valves after keeping it compressed for just one month!
Mind, instrumentally measurable of course, but you see what I mean.
Of course, you're correct when you imply that temperature can affect the creep rate even more, but also time alone can take its (however small) toll.
What I never considered is that the wear you describe can be relevant only upon blipping the engine, as you say.
Considering also that a consequence of accepting your viewpoint is that periodic winter trips to the boat aren't necessary anymore, I'm sold!
OAF
Well-Known Member
Excellent thread with some really good points, very good post from Andy which makes a lot of sense. i operate a fleet of small diesel engined boats 25 to 50hp diesels and come the winter months we winterise them, full engine service and shut them up until the spring without starting them(unless we need to move them or another reason) We have engines that have done 10000 hours and they still keep going well (nearing retirement now)
I have one question, does it really matter what you do as a lot of people probably sell the boat before the engines wear out?
I have one question, does it really matter what you do as a lot of people probably sell the boat before the engines wear out?
lovezoo
Well-Known Member
I think this comes down to personal preferance. If I am not using my boat or car, I will always start the engine every few weeks and let it run up to operating temperature. I also run the boat in forward and reverse gear for a few seconds. To me this makes it more likely the boat will run and the gears will engage when I want to use it. The only times I have had problems is when I haven´t run the engines for some time.
As far as wear is concerned, I can´t see what difference to the engine longevity starting the engine every few weeks makes. Over the course of a season I may cold start the engine 30 times or so, and then another 30 warm starts. Add in 10 or so cold starts over the winter and I have a total of 40 cold starts over the year. Compare that to a car, which gets used every day and you have 600+ cold starts in the course of a year. You wouldn´t expect a car engine to wear out over a year, but that is 10 years or so of cold starts for my boat.
I think I will go on starting the engines every so often and take my chances I will wear them out.
As far as wear is concerned, I can´t see what difference to the engine longevity starting the engine every few weeks makes. Over the course of a season I may cold start the engine 30 times or so, and then another 30 warm starts. Add in 10 or so cold starts over the winter and I have a total of 40 cold starts over the year. Compare that to a car, which gets used every day and you have 600+ cold starts in the course of a year. You wouldn´t expect a car engine to wear out over a year, but that is 10 years or so of cold starts for my boat.
I think I will go on starting the engines every so often and take my chances I will wear them out.
jfm
Well-Known Member
Hi Andy
Thanks for that considered and informative post. I've got a couple of further thoughts which I'd be interested to get your reactions on. And I hope you don't think you're wasting your breath as the guy above (forgotten his name, the one with the GB in the avatar) said, cos you're not. I and others are reading your posts with much interest, thanks.
1. On the question of water made during combustion blowing by and contaminating the oil, I ran my engines today at idle from cold, with the digital fuel flow meters working. The fuel burn was 1.7 lph (these are 2008 volvo D12, 6 cyl, 12 litres, electronic). In one minute of running that's 0.03 litres of fuel, =30cc, = one tenth of a can of Coca Cola. Say specific gravity 0.8 so that's 0.025kg. Now, you get approx 0.8kg of water and 3.2kg of CO2 per Kg of hydrocarbon fuel burned (I would like to cite a reference for that 0.8 but can't find one. I'm going on memory from combustion engineering bit of my engineering. I'm pretty sure it's correct. Will try for a reference later). So my 1 minute of running makes .02kg of water. That's 20cc when condensed to a liquid, a tablespoon and a bit. Now how much combustion chamber gas blows by to the oil? I've no idea but gut feeling says much less than 10% even when cold, else it would be a pretty lousy engine/piston rings. But let's say 10%, so that's 2cc, which is half a teaspoon. Now, my sump has 50 litres of oil. So my one minute of running puts 40ppm of water into the oil (by volume), and if done 4 times over the winter then 160ppm. I honestly don't think that's significant. I mean, elinminating that tiny quantity of water in the oil doesn't justify, I suggest, running an engine cold for a total of say 1-2 hours over the winter, and inflicting the resulting frictional wear. What do you think? Counterargument, correction, comment, etc are very much welcomed
2. On the bearing wear I respectfully disagree your analysis. Hydrostatic bearings work exactly as you say, 100% agreed on that, but you missed out a very important point. There is no significant load on the bearings and hence no significant wear until the engine fires. (Ok, there will be a higher load on the crank bearings that happen to be pushing a piston on its compression cycle, say 1/4 of the time in a 4 stroke, but even that load is insignificant compared to the firing stroke loads). Now, cold engines rotate for a second (or more) before firing - by design in the case of electronic engines and by accident in the case of older engines. During that second or so the oil pump (generally a positive displacement pump, eg a gear pump) does deliver the oil needed to fill the void between the two surfaces of the hydrostatic bearing and so the "one off event" wear in the first second of engine running isn't anywhere near as bad as you describe. In contrast, during the first several minutes of running an engine it isn't hot enough for the metals to have expanded to the right shape, exactly as you describe in your para beginiing "Next" in your earlier post, and it's THIS wear that I seek to avoid by running the engine for 1 minute not 30.
BTW, I fully accept that my running the engine for 1 minute imposes wear, including the hydrodynamic bearing wear that you describe but to a much lesser extent than you describe. I just think it's a price worth paying to sloosh oil around and exercise the rubber components in both engine and g'box. But I am arguing that running the engine for a further 29 minutes imposes 30x (or whatever) more wear and adds no benefit other than removing half a teaspoon of water per 50 litres of sump oil each time
What do you reckon?
Thanks for that considered and informative post. I've got a couple of further thoughts which I'd be interested to get your reactions on. And I hope you don't think you're wasting your breath as the guy above (forgotten his name, the one with the GB in the avatar) said, cos you're not. I and others are reading your posts with much interest, thanks.
1. On the question of water made during combustion blowing by and contaminating the oil, I ran my engines today at idle from cold, with the digital fuel flow meters working. The fuel burn was 1.7 lph (these are 2008 volvo D12, 6 cyl, 12 litres, electronic). In one minute of running that's 0.03 litres of fuel, =30cc, = one tenth of a can of Coca Cola. Say specific gravity 0.8 so that's 0.025kg. Now, you get approx 0.8kg of water and 3.2kg of CO2 per Kg of hydrocarbon fuel burned (I would like to cite a reference for that 0.8 but can't find one. I'm going on memory from combustion engineering bit of my engineering. I'm pretty sure it's correct. Will try for a reference later). So my 1 minute of running makes .02kg of water. That's 20cc when condensed to a liquid, a tablespoon and a bit. Now how much combustion chamber gas blows by to the oil? I've no idea but gut feeling says much less than 10% even when cold, else it would be a pretty lousy engine/piston rings. But let's say 10%, so that's 2cc, which is half a teaspoon. Now, my sump has 50 litres of oil. So my one minute of running puts 40ppm of water into the oil (by volume), and if done 4 times over the winter then 160ppm. I honestly don't think that's significant. I mean, elinminating that tiny quantity of water in the oil doesn't justify, I suggest, running an engine cold for a total of say 1-2 hours over the winter, and inflicting the resulting frictional wear. What do you think? Counterargument, correction, comment, etc are very much welcomed
2. On the bearing wear I respectfully disagree your analysis. Hydrostatic bearings work exactly as you say, 100% agreed on that, but you missed out a very important point. There is no significant load on the bearings and hence no significant wear until the engine fires. (Ok, there will be a higher load on the crank bearings that happen to be pushing a piston on its compression cycle, say 1/4 of the time in a 4 stroke, but even that load is insignificant compared to the firing stroke loads). Now, cold engines rotate for a second (or more) before firing - by design in the case of electronic engines and by accident in the case of older engines. During that second or so the oil pump (generally a positive displacement pump, eg a gear pump) does deliver the oil needed to fill the void between the two surfaces of the hydrostatic bearing and so the "one off event" wear in the first second of engine running isn't anywhere near as bad as you describe. In contrast, during the first several minutes of running an engine it isn't hot enough for the metals to have expanded to the right shape, exactly as you describe in your para beginiing "Next" in your earlier post, and it's THIS wear that I seek to avoid by running the engine for 1 minute not 30.
BTW, I fully accept that my running the engine for 1 minute imposes wear, including the hydrodynamic bearing wear that you describe but to a much lesser extent than you describe. I just think it's a price worth paying to sloosh oil around and exercise the rubber components in both engine and g'box. But I am arguing that running the engine for a further 29 minutes imposes 30x (or whatever) more wear and adds no benefit other than removing half a teaspoon of water per 50 litres of sump oil each time
What do you reckon?
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Hurricane
Well-Known Member
Here's an interesting point that you dont seem to have considered.
What happens to all engines when they stop?
At least one cylinder is left with valves open, exposing cylinders to the external environment.
On boats, there are considerable vents in the side of the engine room and the salty air is particularly harmful to the exposed (untreated metal inside the cylinders.
When I went on the MTU course earlier this year, they seem to think that this was a particular problem.
In fact, their advice is to wrap a dustbin liner around the intake filters when the engines are not in use. Quite easy on our 1200 MTU units becaise they are very accesable but from memory, (in jfm's case) the D12's intake filters can be a bit difficult to get at.
The big problem with this procedure is that you MUST remember to take them off - and I have troubles remembering if I've opened the saecocks let alone remembering to take bags off my filters!!!
MTU also recommended cranking the engines without fireing them. I've never tried this but I believe you can press both the start and stop buttons at the same time on the MTUs to just crank them. They also use this procedure to prime the coolant pumps.
Just my two penny worth.
What happens to all engines when they stop?
At least one cylinder is left with valves open, exposing cylinders to the external environment.
On boats, there are considerable vents in the side of the engine room and the salty air is particularly harmful to the exposed (untreated metal inside the cylinders.
When I went on the MTU course earlier this year, they seem to think that this was a particular problem.
In fact, their advice is to wrap a dustbin liner around the intake filters when the engines are not in use. Quite easy on our 1200 MTU units becaise they are very accesable but from memory, (in jfm's case) the D12's intake filters can be a bit difficult to get at.
The big problem with this procedure is that you MUST remember to take them off - and I have troubles remembering if I've opened the saecocks let alone remembering to take bags off my filters!!!
MTU also recommended cranking the engines without fireing them. I've never tried this but I believe you can press both the start and stop buttons at the same time on the MTUs to just crank them. They also use this procedure to prime the coolant pumps.
Just my two penny worth.
