Running a Diesel at Idle

[bstreep]

One caveat here in all of this. If you own a TURBO diesel, like we do, idling for long periods of time WILL carbon up your turbocharger.

[MarkSF]

What I will do is engage the prop and run at a higher rpm, say 1500, both of which help to get the engine up to a proper temperature more quickly - but not too quickly.

I believe one of the most important keys to long engine life is your warm up procedure - not idling, not under full load - lightish load gets the temp up quickly without causing excessive wear. Remember that oil temperature lags the coolant temperature by a good while, so in my cars I will always drive gently until 10 mins after the coolant has reached temperature. In the boat I will gradually increase the load over about 10 minutes.

[ontherocks83]

Originally Posted by sailorboy1

I bet there are 2 main things that wear out engines: 1 - running them, 2 - not running them

i'll concede to that

[Dockhead]

Originally Posted by sailorboy1

I run my Yanmar engine the the way the manual says to run it. Which means I can run it at at light load/idle as long as I run it up in rpm every few hours. I also run it a fairly light load (2000 rpm) most of the time when motoring because that is the sweet spot of speed/fuel use, but when I do this I also run it up to full load every few hours for a few minutes.

I bet there are 2 main things that wear out engines: 1 - running them, 2 - not running them

Agree entirely.

I have a 100 hp Yanmar 4JH3HTE, turbocharged, intercooled, and with the same specific output as a BMW 2002! It redlines at 3900rpm. I don't like to motor, and when I do, I do it as slow as possible, these days usually 2000 rpm and sometimes even less. I recently did a long Channel crossing from Dartmouth to Roscoff, in a dead calm, motoring at 1800 rpm. Horrible for the engine if you believe they need a minimum 30% load. I ignore that and, like you, do that bizarre thing which is follow the manual! Blow it out every few hours. This seems to work ok.

[Wraith_Mac]

Ontherocks83,
Did you actually read all the posts above your first post or just snippets of them?
I know I wasn't using an 'old adage' but referring to my experience of using, quite profitably, diesel engines, which in the absence of a referenced scientific study may at worst be called 'anecdotal' evidence but not an 'old adage'.
I can't speak for all marine diesel engines but mine operated with the same temperature thermostat installed as the equivalent land based engine, therefore at the same operating temperature.
Many if not most marine diesels operate in a hotter engine room environment than in a truck, yet manage to run at the manufacturers recommended temps.
The emphasis on good fuel, oil and servicing has already been made and I can't see where anybody that has posted, save yourself, that anyone idles their engine for long periods for no reason or treats them [like you somewhat disturbingly suggested] like "some cheap prostitute you thrash on the weekend"
Oh did I already say the maintenance area had already been covered, in the first two posts.
I don't wish to offend but diesels are diesels, there are parallels.
Cheers,
Mac

[zeehag]

i am sooo glad i do not have a turbocharged diesel in either of my boats.i had turbo'd cars--sporty ones--- awesome fun---and much more difficult to manage in maintenance.. i prefer my good old semireliable at present perkins...or should i have called it my soon to again be somewhat reliable old perkins....
one thing for sure--it will be interestingly colorful. pix pending.

[JK n Smitty]

Originally Posted by zeehag

i am sooo glad i do not have a turbocharged diesel in either of my boats.i had turbo'd cars--sporty ones--- awesome fun---and much more difficult to manage in maintenance.. i prefer my good old semireliable at present perkins...or should i have called it my soon to again be somewhat reliable old perkins....
one thing for sure--it will be interestingly colorful. pix pending.

Colorful? Can't wait for the pix

[twinboat]

Originally Posted by bstreep

One caveat here in all of this. If you own a TURBO diesel, like we do, idling for long periods of time WILL carbon up your turbocharger.

Not trying to be a wse guy but can that statement be backed up with any documentation. I have been involved with Turbo Diesels for 40 years and can only recall 1 or 2 that failed, in all kind of situations and conditions. Usual failure was bearing and seal. Make lots of blue smoke.

[Kenomac]

Having burned up one turbo running at lower RPMs and knowing two other Yanmar owners who've done the same, I'd have to say it's important to run your diesel, if it's a turbo, at higher RPMs on a regular basis if you don't want to end up with costly repairs. You really need to blow out all the carbon soot that builds up at lower RPMs. I know the truckers idle for long periods of time, but they also run their diesels hard immediately following their long stays at idle when they get back on the highway.

[ontherocks83]

yes I read all the posts and like I said I'm not looking to start a fight here.

my point on the whole matter is idling = detrimental conditions for your engine (severity and duration can be argued later). I apologize if you took "adage" offensively but my point was unless you tear down your engine and see what kind of condition it is in compared to an engine that was treated differently and wasn't idled in the same manner then there is little water in the statement of it still works fine or that you've had no problems.

my "thrashing" statement (which come on is a funny comparison to how some people treat engines, cars, lawn tractors etc....) was meant to say that in my line of work I see lots of people that abuse their cars by pure lack of knowledge, lack of caring, or that they figure maintenance is just too expensive and never think about how much they just spent on their new car.

I didn't mean to come across saying that everyone I was debating with was guilty of abusing their engines, just that I would rather err on the side of caution and do what is "supposed" to be done to the T rather than think I am smarter then the engineer that designed the engine and figured out the best way to operate it.

Maybe I should have just said read the manual, and if you disagree with what the manual says then call Yanmar and tell them their manual is wrong and that you (I mean "you" as a general term not you specifically) know their design and product better then they do and that they should stop lying to their consumers and that idling really wont do anything bad to the engine. (let me know how that conversation goes)

I don't mean to come off as being snarky even though i'm sure that's how it sounds and if so I apologize. im just trying to make the simple point that through research and first hand knowledge extensive idling for any engine is not good for it

-and maybe its the prior military in me that thinks prostitution jokes are funny but come on tell me you wont think of that the next time you debate whether or not to put off your cars oil change for another 1000 miles

best

[FlyingCloud1937]

Assuming a properly broke-in diesel engine, it is still harmful to run at idle.

But to define idle, is what needs to be done. A diesel that is started and left to idle without any load will do a couple of things that are very bad. One all injector pumps and injectors are designed to govern fuel at rated loads.

They are very inefficient at low speed/idle. In that they inject more fuel at each compression stroke then they can efficiently burn. This leads to higher nox and carbon deposits, it also washes the cylinders, which results in gums and varnish and leads to diesel contaminated oil.

Along with that the acids created by the unburnt fuel are harmful to all the bearing and other friction surfaces. As well as creating moisture in the oil. Along with this additional inefficiencies of the pump/injectors at low speeds is the flame spread during the combustion cycle which helps exacerbate the rich running.

To confirm this all you need do is look at the HP/Torque curve of your engine, and then compare it to the fuel burn/efficiency curve. The work done per gram of fuel increase as the speed/load and work done increases.

So we can all agree that an idling diesel engine is not good for long term health. Just because some trucker does it doesn't mean it's good for the engine. Nor is running an engine lightly loaded at any speed, this is exactly why truckers have 18 gears. Not to mention that almost every country/state has anti idling laws, which are enforced.

Now we can run an engine at low speeds as long as we have a load on the engine, and it's not really idling. It's actually doing work. So go back to your HP curves and note the HP produced at the various speeds, and try to match loads/work being done. This will help, as it will cause the exhaust gas temperature rise above 300F, this means that the cylinder temp is high enough that it's burning more efficiently, then at idle which is usually below 270F. Any EGT below 300F means it's wet stacking/running rich and is bad for the engine. Ideally a diesel should be running higher then 550F, and max efficient burn is in the 700-900 EGT depending on the engine.

Constant speed governors such as for a generator, operate differently then a variable speed governor, even if the two engines are the same. They are tuned to provide the best results for which they were designed to run.

This is easily confirmed by noting that an engine rated by the EPA to run at constant speed won't meet EPA for a variable speed, and vise-verse. And if that is not enough just give your local injector pump rebuild shop a call and ask them if you can replace one pump for another.

Hope this will get the topic/discussion going in the right direction.

Lloyd

[David M]

Cummins told me that the more a Diesel idles the shorter its lifespan will be. I think Cummins knows a thing or two about Diesels and would have no reason to lie to me about this.

[Wraith_Mac]

ontherocks83
Ok, all clear sounded. LOL
To put it short, apart from my own companies, I managed transport related enterprises, my brother's 45yrs in the trucking game and my fathers before him, I also held senior positions within the spares and service HQ of two of Australia's biggest Japanese engine users/distributors.ie. Toyota/Hino and Nissan.
Their base engines are also some of most used for maritime conversions in the world, I stand by everything I said about the use of diesels in both the land based and maritime environments.
What I said is based on my experience, that of my colleagues, warranty claims and reports to Japan.
The above positions all required actually working on engines, diffs, gearboxes etc. at some point. Mechanics here will not listen to you unless you can get your hands dirty.
What these exercises did was collect the data to write the manual.
There is quite a link between Yanmar and Toyota.
I am not going to go any further into my background as I'm now retired and this is a public forum.
I hope we can agree to disagree as gentlemen on what is the worth of experience?
Cheers,
Mac

[Mr B]

I sold my AS 400 Diesel Mobile welder, As the small electrodes that I was using were not big enough to load the motor up when working,

This was detrimental to the motor, as the Bores would glaze up resulting in a very smoky motor,
I sold it and replaced it with a smaller Mobile welder,

The difference between a marinised motor and a normal car motor,
Is only the Oil and exhaust is water cooled, as an extra cooling process, I have built a couple of marininsed motors,

The reason trucks and big diesels idle for long times at truck stops, Is to keep the motors hot and full of oil, Turning them off, Is more trouble than its worth,

The big diesels in trains, If they have to stop, They will leave them idle for 48 hours, They wont turn them off for less than 48 hours,
The B class diesel engines in Victorian Trains Snapped crank shafts, If left to cool down, and then restarted cold, They left them running,

Diesels do need to be loaded up and driven hard every now and then just to blow the carbon out of the cylinders, And to reseat the rings, Adding to the life of the motor,

A diesel truck motor in a long haul truck gets rebuilt every 3 to 5 million miles on the road, They also crank up 500,000 miles in six months,
So comparing a truck and a recreational boat motor is just not applicable.

Your motor will be loaded up, when you motor in and out of your port, So that covers the idling times,

[Jim Cate]

Originally Posted by Mr B

A diesel truck motor in a long haul truck gets rebuilt every 3 to 5 million miles on the road, They also crank up 500,000 miles in six months,

Wow,Mr B, you sure know some boss truckies, for that equates to about 2750 miles per day, or around 115 mph average 24 hours a day for six months.

That's TRUCKIN"... or maybe you just made up that "fact"?

Jim