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Old 26-05-2007, 02:24   #16
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Torque is a difficult one to nail down. Hp is easy to achieve. Very losely, It tends to be a direct result of the CC rating of a vehicle. Torque however, is a direct result of the engine design. Torque is a measure of rotational effort. But how it is derived is from the power delivered over the time of the stroke. So length of stroke and the time the fuel is burning and producing power in the cylinder have an affect on torque output. The fuel burn time varies as the engine varies it's revs. Burn time and the power derived by the burn can be varied greatly by the cylinder design(piston and head shape) and by the way the fuel and air enters the chamber. The variation is not linear. There are "power bands" in an engines RPM that alter those burn times and thus the Torgue curve varies. Stroke has a large influence as well. Short stroke high reving engines tend to have a flater torque curve. However, the single biggest influence and change in todays modern engines are the injection system. Computer controlling the fuel entry has made major leaps in creating and maintaining flat torque curves.
Old NA engine systems tend to have a very steeply ramped curves in both Hp and Torque. And these ramps are often opposing one another. This is because a NA engine is poor at getting a good ratio of air into the system and the govoner on the fuel pump doesn't know that.
So take a forced air engine, a computer controlled injector system and fit them to a high speed Diesel and you end up with the modern torque curves we see today.
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Old 26-05-2007, 10:01   #17
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Quote:
Originally Posted by cal40john
Yanmar doesn't care if you run higher rpms, they just imply that if you run lower, you can eventually damage your engine. I don't know what Cummins recommends.

I cant tell you how many times I have heard and seen this.
So many guys in the winter come down to the dock and will fire up the diesel for a while.But in reality far from doing the engine any good it damages them.
Boating of all kinds seem to include a fair bit of engine abuse by absence.
Diesel really dont like it.

To be kind to that diesel smoker .....you need to get in the boat and go push it around for a while.Which is an irony if your a sailboat enthusiast thats for sure.
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Old 26-05-2007, 14:02   #18
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75/75

Seems to me I read somewhere that a diesel engine should be run at 75% power for 75% of the time in order to keep it happy and help it live a long life. If run mostly under 75% power then things like oil and filter changes should be done more frequently than manufacturer's spec. Also if motoring at mostly lower power it helps to at least run the first and last 1/2 hour or so (allowing for warm up and cool down) at 75% or higher in order to flush out the carbon and heat up the oil.

Perhaps Pat would like to comment on this post...
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Old 24-08-2007, 22:26   #19
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New to forum and was searching diesel additives for the new ultra low sulphur diesel that is sold in USA / Canada. Looking for what brands that are being used by boaters to add lubricity.

Also read about various posts about smoke from diesels, my boat has a Yanmar 4JHE, runs and starts great, however, it emits a slight blue smoke on start, it is worse in cold weather but goes away when warmed up and under load. It does not use any oil that I can detect between oil changes, roughly 100-120 hours. I drain it and I get the quantitiy out that I put in, about 5.5 litres. I have also read that as diesel is an oil, it can burn blue on some occassions too. I have seen new construction equipment start up in cool weather and emit blue smoke for a while. Perhaps my injectors need attention but if they did wouldn't the blue smoke be there under load and with a warm engine ?
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Old 25-08-2007, 00:54   #20
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Firstly to the additive question. Don't worry yourself about it. Use a good quality oil for lubricating the engine. The fuel should have had alternatives added for meeting specs.
Yes you will see blue smoke. It is normal. If the smoke is exccesive, then you have an oil burn problem. Make sure you follow the advice of how to warm up your engien in the sutdy hall paper at the head of this Topic Forum.
Injector issues will show up as black smoke.
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Old 25-08-2007, 04:14   #21
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Thank all of you for the great remarks. As a diesel mechanic and lifetime diesel user I can add little to this discussion except to follow the manufacturers suggested maintenance schedule. I wish that I didn't need an engine aboard and run it as little as possible, as this is a sailboat damnit and not a trawler. After 10 years I have 180 hours on the Yanmar hour meter on my PSC 32' Pilothouse.
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Old 25-08-2007, 20:43   #22
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Diesel is indeed often called "fuel oil" because it is both a fuel and a lubricant. Remember that Dr. Diesel's engine was designed to run on peanut oil, and it was just a sad coincidence that cheaper petroleum products were coming on the market as his engine was being put to use.
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Old 26-08-2007, 00:35   #23
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Quote:
Originally Posted by hellosailor
a1-
Diesel is indeed often called "fuel oil" because it is both a fuel and a lubricant. Remember that Dr. Diesel's engine was designed to run on peanut oil, and it was just a sad coincidence that cheaper petroleum products were coming on the market as his engine was being put to use.
And now we are going full circle back to the vegie oil

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Old 26-08-2007, 12:23   #24
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We have a local guy that runs a upper grade auto repair shop and teaches at the area Technical / Trade School and also has a Radio program every Saturday AM that is interesting. One of his "pet" projects is running Diesel cars on used oil from some of the larger restraunts... which he was getting for free for many years now they find they can sell it to companies that set up collection routs and he has to pay... or give them free ads on his radio show.

I have seen him putting around town in one of his "will you have Fries with that" cars. It seems to smoke a bit and I think I may have only imagined it but when behind him I think I do get the aroma of a fish fry??? Probably only mental picture but it seemed real. He has a small following locally of people converting cars to veggie oil fueled vehicles. Think he once gave a web link to a recommended process for making modifications.

Not sure it would help in a boat... fewer restaurants to pull up to for a fill up than diesel pumps. Except maybe down the slot between West Palm Beach FL and Miami... you have hundreds of restaurants you could probably get fill ups along that ditch.
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Old 26-08-2007, 14:28   #25
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OK, An engine question for the experts. 4JH3E that runs like a champ, starts the first time you hit the key and shows NO SMOKE when running other that a small amount at initial start up. But a slight mystery, when running the engine for eight to ten hours about a 1/4 or a little less oil seems to disappear somewhere. The engine currently has 1200 hours but this has been the case since new. It gets oil and filter changes every 100 to 125 hours religiously using good grade 15W 40. Average cruising RPM's are 2500 to 2800 with some time run at 3200. Any thoughts?
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Old 26-08-2007, 21:00   #26
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1/4 of what? 1/4 of a quart, 1/4 of a gallon, 1/4 of the contents?
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Old 27-08-2007, 00:25   #27
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What oil weight is recommended for that engine??? Ensure you are not running an oil with a too light a number. If the spec is for say a 20w40, then 15w40 maybe just a little on the light side. Some may not notice their engines using and others will. It just depends.
Ensure the engine is worked hard. 1200hrs is only just run it. You will expect some oil use before the rings are truely bedded in. Get the engine into gear ASAP and work it hard for a while and then see if the oil use becomes less.
And finaly, remember that 100hrs is a long time. It is equal to 10,000Kms for most raod vehicles. So after 10,00Kms, I would expect to see just a little use. But as Dan said, 1/4 what??
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Old 27-08-2007, 03:21   #28
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I reckon a car averages around 75kph on a trip. So 100 hours would be around 7500kms evquivelent. We have done 165 hours now. Must be time to think about our 3rd Volvo
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Old 27-08-2007, 09:00   #29
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I cruise in a single engine trawler. Therefore keeping my diesel engine in tip top running condition is of utmost importance to me. My engine is a John Deere 4045TFM, a turbocharged 4 cylinder rated at 120 hp at 2400 RPM.

I have had extensive discussions with the engineers at John Deere. Here is what they tell me. Run my engine at 60% to 80% of maximum rated RPM (in my case that is 2400 RPM).....80% of the time. And I have found that 60% to 80% is in fact my 'sweet spot' where I get the best fuel economy and smoothest running. John Deere's formula is consistent with all the marine diesel manufacturers today, including Yanmar.

By the way a boat that is correctly propped will get the maximum rated RPM's at WOT, no more, no less. If you get less than maximum rated RPM's at WOT then your boat is over-propped. If you get more than maximum rated RPM's at WOT, then your boat is under-propped. This applies to both sail and power boats.

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Old 27-08-2007, 10:13   #30
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Chuck, I would suggest the first question is whether the oil is being consumed internally--versus leaked externally. If you start with a clean engine bay and fine no evidence of external leaks (bearings, covers, anyplace?) and no oil trickling down anyplace, it is being consumed. And then the only question is where or how.

Could easily be just getting sucked past the rings. I don't know that engine, perhaps the break-in hours weren't run quite right. Or perhaps that engine is just supposed to consume oil. Mercedes used to build diesels with loose rings, intentionally. They said if they used loose rings and consumed a little oil (a liter/1000 road miles) the rings and cylinder walls would last forever, and that fresh oil was a good cheap way to get engine longevity.
Could be worth asking the maker what is normal for your engine, before looking to see if this is not.
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