Running engine w no load

[jleonard]

I think the point is that glow plugs do not heat the water jacket. They have nothing to do with the car's heater.
They pre-heat the combustion chamber prior to starting. Once the starter is engaged they are not powered.
I had a 1980 rabitt diesel and we currently have a 1999.5 Jetta TDI. The old one ran cold at idle, but the TDI warms up just fine in Ct on a cold morning although a little smokey at first.

 

[Xsbank]

Wrong. I made it clear that the coolant heaters were called glow plugs, even though that made most of you think I'm a moron.

Glow Plug Style Coolant Heater: TDI 96-04

Item #: 19041
Details: VW TDI glow plug heater. This TDI glow plug heater is an exact replacement for your factory coolant heater (installed in water flange). They are sold each, 3 are required per vehicle. Note: not all TDIs have this feature.
Fits: Jetta 1996-2004, Golf 1996-2004, New Beetle 1998-2004

 

[RickB]

Wrong. I made it clear that the coolant heaters were called glow plugs, even though that made most of you think I'm a moron.

The point is that sticking a glow plug in the coolant path for a few minutes during warmup is a long ways from keeping the engine temperature at its "design temperature."

Look up the specs on those things, together they put out around 5-600W for a couple of minutes until the coolant is around 100F then they are finished for the day. The idea was to aid the emissions system at start, not to maintain engine temperature at low load.

 

[Xsbank]

Wrong again. If you got stuck in traffic at minus 20 the heater would not be able to even clear the windscreen so the heater plugs would come on again to add some heat. The only thing stopping you from freezing your @ss to the seat was heated seats. The engines had no surplus heat for you.

This is all moot. The point is, diesels are very efficient and need a load to attain design working temperatures otherwise they are being damaged. I say it again, if you want to just noodle about and rarely get the engine up to its torque peak then you should be running gasoline because the diesels will not last any longer and they are way more expensive to repair. Load them until they are near torque peak or full operating temperature and you will get thousands of hours out of them. Take a long look at the boats for sale: "...has twin Detroits, port 600, starboard 1400." The ads are full of such examples. Guess how these engines were run?

 

[psneeld]

Wrong again. If you got stuck in traffic at minus 20 the heater would not be able to even clear the windscreen so the heater plugs would come on again to add some heat. The only thing stopping you from freezing your @ss to the seat was heated seats. The engines had no surplus heat for you.

This is all moot. The point is, diesels are very efficient and need a load to attain design working temperatures otherwise they are being damaged. I say it again, if you want to just noodle about and rarely get the engine up to its torque peak then you should be running gasoline because the diesels will not last any longer and they are way more expensive to repair. Load them until they are near torque peak or full operating temperature and you will get thousands of hours out of them. Take a long look at the boats for sale: "...has twin Detroits, port 600, starboard 1400." The ads are full of such examples. Guess how these engines were run?

You don't know and neither do I....

Your absolutes are just as bad as someone who says running a diesel at more than cruise for a few minutes here and there will destroy it also.

Most engines defy mechanics and engineers for how long they actually last if someone doesn't intentionally kill it by letting an ancillary system do it in or by ignoring obvious symptoms and keep on pushing it.

 

[Nomad Willy]

Xsbank,
Wow where'd you come from? West Van I see. I lived in an apartment at 1831 Robson st in the west end for awhile. Recently we ate at a Korean restaurant that was wonderful on Denman Pl .. close to Robson.

Xsbank gasoline and diesel engines are just about equal in efficiency at WOT. But a 100hp engine run at 25hp is considerably less efficient that a 35hp engine run at 25hp and as you point out a lot better for the engine. A lot of guys here are running 120hp engines at the 25hp level and I have yet to hear of any failures re running at slow bell. So it's not instant death but quite far from ideal. I've been pro running diesels hard here on TF since 07 and get nothing but flack from most. You will too but it's a bit like telling someone they don't know what ther'e do'in so you can expect that it won't be the most pleasant experience. Good luck and no I didn't know that about VW diesels. I have a Golf and prefer gas engines. Drove a new Jetta diesel for a day and was very impressed. Never woudda believed it.

I suspect this is your coming out party so WELCOME.

 

[Datenight]

I had a 1980 diesel Rabbit also. Put 186,000 miles on it in six years. Heat in Connecticut winters was never an issue. Did use a block heater for starting on those cold January and February mornings.

Rob

 

[sunchaser]

XS

This is the essence of the thread. Provided book oil and coolant temperatures are achieved, what difference does it make if our diesel propulsion (not gensets or VWs) engines only operate at 20 or 30% load?

 

[AusCan]

What I believe is a big factor to engine life is number of starts (duty cycles).

I used to manage a bunch of power stations that ran Caterpillar 3516 driven generators.
We had almost 1000 of these engines in service throughout the world, and so had the numbers to make valid fact-based comparisons regarding maintenance.

About half of these Cat 3516's ran non-stop, shutting down only for servicing every 1000 hours. The other half ran only during peak demand periods, shutting down for 8-12 hours every day. All engines ran at 90-98% load when on line. The difference in average maintenance cost & engine life was huge.

The engines running non stop were averaging almost 50% more hours before requiring a rebuild. Items such as exhaust manifolds lasted over 10X as long with the extended running engines. The life cycle of some components were directly related to number of starts, rather than engine hours.

I know some boat users start there engine(s) once a week and bring it up to temperature then shut it down. I suppose it spreads a bit of oil around and prevents the cylinder walls from rusting, but is it really a good idea?

 

[RickB]

Ever owned a Golf TDI Rick?

I just saw you are in Lauderdale where cars don't even have heaters.

Well, as a matter of fact, yes. I owned two of them when I lived in Hamilton, Montana where -30F in the winter was fairly common. Both survived well beyond the 200,000 mile marker without benefit of supplemental coolant heating after startup and probably rarely exceeded around 50 percent rated power output.

And I regularly use my car heater down here in the winter.

Most of us who ran diesel cars or trucks in that area used block heaters overnight to keep the engines above +40 or so and put a sheet of cardboard over the radiator for most of the winter. There were many times the car was a bit crisp and there was more ice inside than out but it never bothered the engine at all.

You're barking up the wrong tree, old boy. The cooling system on a marine diesel makes it relatively easy to maintain adequate temperatures for low load running. Most diesels used in recreational boats have difficulty staying cool at high loads because of the simple cooling system design.

The efficiency of a diesel is nearly constant across its load range. The thermal efficiency of a diesel is actually higher at part load. The diesel is around 70 percent more fuel efficient at part load than a gasoline engine at part load. There is no condition in which a gasoline engine is equal or better in efficiency than a diesel. The high efficiency of a diesel is not a problem in any respect, and certainly not in regard to cooling or maintaining adequate engine temperatures.


There is a shipload of anecdotal evidence backed up by maintenance history that shows the positive benefits of a diesel operating at higher coolant temperatures and constant load (even if that load is down around 25 to 30 percent) to support an argument against idling an ice cold engine for days on end. So what? I suspect very few recreational boat owners operate their engines that way.

 

[Xsbank]

Actually, the barking seems to be coming from Lauderdale.

A Lehman will never reach full operating temperature at idle.

Never, unless it is faulty. A Lehman should be run at WOT at regular intervals according to the guy that designed it, Bob Smith.

I never said a gasoline engine was more efficient than a diesel, I said that a gasoline engine was happy at idle, would need an overhaul at approximately the same time as diesels run unloaded but the overhaul costs would be significantly lower on a gas engine; I suggested if you don't want to load your engines you would be better off with gas.

The point of discussing diesel efficiency was to make it obvious that precisely because of that efficiency you needed to load the engine to produce enough heat to allow the engine to run at design temperature.

In fact, the "so what" is your suspicions are wrong, some denizens of this site have asked or already start their engines in winter and idle them for some time, never reaching operating temperature and they were asking if that was a good practice.

For a diesel, no. In my opinion It is tantamount to abuse.

 

[Gibraltar]

Hi the worst thing you could do is run your diesel off load. It will glaze the cylinders and clog the rings and if you have an inter cooler and turbo they will fill up with soot. I have seen lots of sea going boats on the Thames in the UK, they are big engine boats that are run all the time at just in gear due to the 8kt speed restriction.
When you take them apart you find the turbo clogged up with soot closing a 6 inch exhaust down to 1 inch jammed up with black carbon. When you check the compression you find it well down, which makes starting harder and smoking exhaust when running and a carbon build up in the valves.
The older engines are not as troubled by slow speed/off load but still should always be run on load, but the modern engine are much more sensitive, they are made for performance and are designed to be run at set rpm and temps.
The best thing for your boat and you is take it out and enjoy it!

 

[RickB]

Generators are the most problematic service when runnning at light loads. However, the diesels which are used to drive generators are not so tender as all
the-sky-is-falling crowd here want to believe. ​

Let me quote Cummins: "Cummins Power Generation does not recommend running generator sets at less than 30 percent of rated load."​

Modern common rail engines are far less sensitive to low load running than the mechanically injected engines. The CAT C18 for example can develop 450 horsepower at 1800 rpm. Max trolling speed for that engine is 900 rpm - that is maximum, not minimum - the minimum is 750.​

At 750 rpm that engine puts about 40 hp into the prop .... at 900, just under 60hp. Do your own math for the percentages. While you have the calculator out, punch in 873 hp at 2200 rpm for the more powerful rated version of the same engine. That one puts out a whopping 42 hp trolling all day at 800 rpm. The point being all this misery about "underloading" is a bunch of crap for the type of service the engine in a recreational trawler will ever see.​

Old mechanical engines are more "troubled" by low load running but their troubles are not half as bad as some people are so desperate to believe and convince others. The new CR engines don't even knit a brow over such things. ​

 

[Baker]

The bottom line is the way most of us use our engines will provide many thousands of hours of service out of our engines. As long as they get up to operating temp they will be fine. And in most trawlers, that is likely anything IN GEAR AND ABOVE IDLE power setting. XS, to say that if you don't run your boat loaded all the time or it will suffer an early death, I think it has been proven over and over and over, that is not true. Most people have been running these Lehmans and Perkins forever at 25-40% and they get thousands of hours of service. In fact, I would say that these types of engines have the highest longevity of any in (recreational)marine service BECAUSE of their low loads. Please read I am not saying they are underloaded as they get up to and stay at normal operating temps. Detroits die an early death because people run the piss out of them and probably don't know how to maintain them. I own Cummins and they are squeezed pretty hard...and I run 'em hard. The Cummins don't seem to last as long simply because people run them hard and don't know how to maintain them(aftercooler maintenance likely being the number one cause as well as being OVERLOADED by improper prop pitch).. If your theory was correct, Detroit and Cummins would have the highest times between overhaul and/or replacement. They don't. I would not flinch if I bought a boat with Lehmans with 3000 hours on the engines. I would be extremely concerned by a Cummins(6bta) powered boat with that many hours.

As FF has always said....engine life usually has a lot to do with how much fuel has been run through it(assuming good mtx). And I believe there is a lot of truth to that statement. You cold probably add to that...how much fuel has been run through it in relation to it's displacement. A Ford Lehman 135 has almost exactly the amount of displacement of my Cummins. It produces 135hp whereas my Cummins produces 330hp. My engine run at 75% power versus the Lehman at 35% power. My money is on the Lehman for longevity. For a fixed amount of hours, I am running 3 times more fuel through my engine...which equates to 3x more work being done. And a very well maintained Cummins can go 5000 hours....while a very well maintained Lehman can go 15,000 hours. I don't think that 3:1 proportion is random!!!!

There ain't no free lunch!

 

[Xsbank]

I think we all agree that "loaded" means full operating temperature. If you are running your engine at 25-40% and it's fully warmed, and it's in gear, it's loaded. That is why if you go way back in this discussion you will read the assertion to warm up in gear, not at idle.

An argument is when you try to persuade the other party to agree that your position is the best one. You have not managed to convince me that I am wrong, but you are also too hidebound to accept my opinion. So basically we are wasting our time. Owners will continue to do precisely what they want to do no matter what my or your opinion is. Unless somebody is employing you to operate their engines, you will likely just do whatever you have been taught or whatever you think is right. Kind of like all that wasted gum-flapping that your Congress seems so good at these past weeks.

Just like what I will continue to do with my engine.

It would be interesting for those owners who had a Cat or a Detroit rebuilt at 600 hours, what happened to the engine? Willing to share? I know some, like the 8.2s had design flaws, but what about the rest?

 

[Baker]

I think we all agree that "loaded" means full operating temperature. If you are running your engine at 25-40% and it's fully warmed, and it's in gear, it's loaded. That is why if you go way back in this discussion you will read the assertion to warm up in gear, not at idle.

An argument is when you try to persuade the other party to agree that your position is the best one. You have not managed to convince me that I am wrong, but you are also too hidebound to accept my opinion. So basically we are wasting our time. Owners will continue to do precisely what they want to do no matter what my or your opinion is. Unless somebody is employing you to operate their engines, you will likely just do whatever you have been taught or whatever you think is right. Kind of like all that wasted gum-flapping that your Congress seems so good at these past weeks.

Just like what I will continue to do with my engine.

It would be interesting for those owners who had a Cat or a Detroit rebuilt at 600 hours, what happened to the engine? Willing to share? I know some, like the 8.2s had design flaws, but what about the rest?

It was likely due to fuel cooler failure...after cooler failure....or OVERloading. I very seriously doubt a diesel engine is gonna fail in 600 hours due to under loading. Ask the experts. Most will tell you that they have never seen an engine fail due to underloading.

My "opinion" is based on facts. Show me one failure caused by underloading?????....just one!!! You can't because it doesn't happen. Engines fail for many reasons. Underloading is NOT one of them Just accept it and let's move along!

 

[Edelweiss]

you will likely just do whatever you have been taught or whatever you think is right. Kind of like all that wasted gum-flapping that your Congress seems so good at these past weeks.

O-o-o-w-w-w!! That was hurtful!! I just wish we could get them to have fist fights and brawl like other countries. At least we would get something for our money!!
Fistfight in the Ukrainian parliament - CBS News Video

 

[Nomad Willy]

My engine gets up to 180 coolant temp after about 3 minutes of running at 1000 rpm in neutral. Nowhere near warmed up for cruise load (50%).

Lube oil temp is much much closer but I'll bet that even lags behind a heat soaked engine. The most important things like valves and pistons probably heat quite soon though.

Re the underloading potential downside what is there besides cyl glazing and ring sticking? From what I've read ring type determines most of the glazing issue. Or is it sideways force on the piston? So possibly having a certain ring type can be a great deal of insurance. But piston heat comes from fire in the hole (mostly) and only load will bring that about. So is keeping the load high enough to keep the oil temp high enough to keep the rings free and clean basically all there is to it?

Perhaps a lube oil system that is thermostatically controlled like the cooling system in my engine could be a good feature. That's my wild idea of the day.

 

[RickB]

I think we all agree that "loaded" means full operating temperature.

Why would anyone think something like that? A load is a load and temperature is temperature. Sometimes they happen to meet, sometimes they don't.

There are plenty of generators operating at "full operating temperature" with no load whatsoever and plenty of propulsion engines overheating at low loads or idling well within the temperature range defined by the manufacturer as the correct operating temperature.

 

[Xsbank]

I didn't suggest that the 600 hour engines were underloaded, I merely asked for some evidence. Reading comprehension seems to be a weak link on this site.

Enjoy your boating.

 

[sunchaser]

You have not managed to convince me that I am wrong, but you are also too hidebound to accept my opinion.

XS

Some of us have expressed in the past our relative experiences, not a lot of detail mind you, but a hint as to our creds. Just curious, what are your diesel experiences?

BTW, I was working in Canada when the French Canucks went nuts and tanks were rolling in the streets. I much prefer loudmouth know nothing's to the business end of a cannon.

 

[Baker]

I didn't suggest that the 600 hour engines were underloaded, I merely asked for some evidence. Reading comprehension seems to be a weak link on this site.

Enjoy your boating.

Well then what are you suggesting? I suggested some causes. I am heavily vested in the iron that is down in my bilge...like most of us are. Which means I do a lot of reading. I have learned a lot since that iron could cost me a lot of money to replace. Those 3 things in my post are some of the more likely causes of premature failure in Cummins engines....and likely the engines you listed. Diesel engines don't fail early for no reason. And marketing drives the engine types for recreational boating....IOW...highly powered "light" engines for boats that plane....which is kinda where this thread has crept... Maybe my fault. But engines put in boats that are not meant to plane are even less likely to fail prematurely.

 

[Xsbank]

Interesting about Cummins. I'm in the process of buying a 250 hp 6CTA83-MI. Just one.

 

[Northern Spy]

The Gwaii Haanas is an interesting looking boat.

 

[Xsbank]

Don't own it yet, haven't done surveys or trials yet so I don't want to jinx the deal. But yes, it is cool, I'll never see another one, which is why it's difficult to buy.

 

[Baker]

Interesting about Cummins. I'm in the process of buying a 250 hp 6CTA83-MI. Just one.

That is interesting that you posted that because I was going to mention something about engine "ratings". I am not familiar with the 250hp version of the 6CTA. That means that engine is very significantly derated. The highest power version of that engine is 450hp...if I am not mistaken. Think of it this way....you are running the 450hp version of that engine at a little over 50% power...and that is assuming you are running it 100%(250hp). That engine will last forever at that rating!!!! And even the 450hp versions are pretty stout engines and are not boosted as heavily(per liter) as my 6BTA.

 

[FF]

To me the best way to select an engine for >forever< operation is to go to the MFG site and look at the lowest power rating for that engine and find its 24/7 rating.

If that (HP/RPM or less) is where you will be cruising ,,amusing yourself purchasing a rating 50% or even 200% higher does no harm.

AS long as there will be some positive boost at cruise a pair of turbos , and intercooling will do no harm.

And you might get a blast once in a while defueling at 1/2 NM/ per gallon , and tossing a fish killer sized wake.

 

[Baker]

To me the best way to select an engine for >forever< operation is to go to the MFG site and look at the lowest power rating for that engine and find its 24/7 rating.

If that (HP/RPM or less) is where you will be cruising ,,amusing yourself purchasing a rating 50% or even 200% higher does no harm.

AS long as there will be some positive boost at cruise a pair of turbos , and intercooling will do no harm.

And you might get a blast once in a while defueling at 1/2 NM/ per gallon , and tossing a fish killer sized wake.

Or you can derate it "yourself". Just don't operate the engine at the higher power settings.

 

[Nomad Willy]

"Or you can derate it "yourself" ".

Hmmmm For one I don't know more about rating an engine than the engine manufacturer. I'm inclined to follow the recommendations set forth by the manufacturer.

 

[Baker]

"Or you can derate it "yourself" ".

Hmmmm For one I don't know more about rating an engine than the engine manufacturer. I'm inclined to follow the recommendations set forth by the manufacturer.

I think you missed the point, eric... Engines are rated by the manufacturer for a specific purpose. Recreational Marine diesels are usually in the higher ratings because that is what the market demands. But in the case above...you have basically the same engine....one is rated at 450hp...the other at 250hp. You could just operate the 450hp engine(ie say 150hp) in the same manner you operate the 250hp and you have basically derated the engine yourself!!!! simply by the way you operate it. Engine manufacturers derate engines for longer life and longer maintenance intervals. That is why you hear about generators that run 100% 24/7. The engines that run those generators are likely very capable of producing significantly more power than their 100% rating. But the manufacturer derates them so they can be run at "100%". If you think they are running balls out on the ragged edge like it sounds, you would be mistaken.

To put it more theoretically, the (de)rating is somewhat arbitrary.

Go easy on me Rick!!!!