Extended idling vs switching on and off

[Cherokee140]

Makes me wonder just how much of this is politically correct and how much is mechanically correct. How often have you seen diesel engines left to idle? Tractors, OTR trucks, fork lifts....

Me thinks that a great amount of this is hear say and fears to make us shut down to "save mother earth"....to **** if it is harder on the machine.

But I can tell you what I do, on my brand new machine and the older one. If it is for longer then 10min or so I will shut it down. Going inside for lunch shut down, going inside to recycle some coffee no shut down.

 

[Blade Breaker]

I agree with you about the "politically correct" part. If diesel engines were so fragile that if they idled for more than 3 minutes they would fail that would be a horrible design. And I get a kick out of the people that wont let there diesel trucks idle in the morning to warm up when it is -20 out. In the winter I go out and start my truck then go in and take a shower. 30 minutes later its still running and have not had a failure for 15 years.
I do agree with not having the machine slow idle when it is cold. It warms up faster at about 1100rpm.

Makes me wonder just how much of this is politically correct and how much is mechanically correct. How often have you seen diesel engines left to idle? Tractors, OTR trucks, fork lifts....

Me thinks that a great amount of this is hear say and fears to make us shut down to "save mother earth"....to **** if it is harder on the machine.

But I can tell you what I do, on my brand new machine and the older one. If it is for longer then 10min or so I will shut it down. Going inside for lunch shut down, going inside to recycle some coffee no shut down.

 

[dave1949]

The 2003 Ford 6.0L diesel I used to have would automatically kick up to a high idle when cold started. It would happen within 30 secs. to a minute after starting, and stay at high idle until the accelerator pedal was touched. My '11 Dodge Cummins with manual trans. doesn't do that, nor does it have a manual throttle control knob. I wish it did.

 

[PapaPerk]

Most of the extended idle mentality is from old way of thinking on old engines. Old diesels are a pain to start and easier to just let run... Stuff like pony start dozers, tractors and big trucks.

But new modern diesel don't benefit from sitting there idling for hours on end. But hey it your money ur sending up the stack so idle to your hearts content. If its gonna be more than 5 mins at idle I shut it off.

 

[Blade Breaker]

That is strange that the Dodge does not have a faster idle when cold. Even old cars had a high idle when cold.

The 2003 Ford 6.0L diesel I used to have would automatically kick up to a high idle when cold started. It would happen within 30 secs. to a minute after starting, and stay at high idle until the accelerator pedal was touched. My '11 Dodge Cummins with manual trans. doesn't do that, nor does it have a manual throttle control knob. I wish it did.

 

[MHarryE]

Just thinking through the theory. Gasoline engines intake a fuel/air mixture at the stoichiometric ratio evenly disbursed, about 14.7:1 or 15 parts air to 1 part fuel. When that vaporized mixture hits cold cylinder walls the gasoline can condense; therefore, an enriched ratio at cold temps ala choke on an older carbureted engine or computer programmed enrichment based on temperatures for a fuel injected engine.

Diesels don't care about the stoichiometric ratio. They always get cylinders full of air and then just enough fuel to keep the engine running at the governed speed whether it is controlled by a mechanical governor or computer. Instead of 14.7:1 a diesel may be running at 150:1 at idle, but this varies from engine design to engine design, will differ more between a direct injection and indirect injection engine.

Newer fuels are cleaner, leave fewer deposits.

But engines do like a more or less constant temperature. In general pistons are an aluminum alloy, blocks and heads are cast iron (for ag tractors), bearings are of differing alloys, etc. When you shut down the engine it begins to cool with the various parts cooling at different rates. Clearances change. When restarted it once again needs to warm so components are at their normal clearance but also realizing the engine is designed to have proper clearances at all working temperatures. So it would make sense to keep the engine at a constant operating temperature and not go through a number of heat/cool cycles.

Conversely even at idle and with an oil film between moving components operating time equals wear. Not much wear at idle but still wear.

Also if you intend to trade in your tractor you will get more money for a low hour machine.

In the real world having had hundreds of test machines operating mixed in customer fleets during a time span, often 2 years, prior to new product introduction I found that a typical large paving contractor will have a person start the engine of every machine in the fleet early in the day prior to all of the other crew members arriving on the job. The engines then run all day even if something in the chain of machines breaks down and everybody has to stop. Some operators do stop their engines, most don't.

After all this I don't believe there is a definitive answer. I know you can hear all kinds of expert opinions but having been involved with engine design and production from starting with a clean sheet of paper to analyzing the results after years of production the best answer I have is you can do whatever you want.

One extreme operation I still remember is a machine in one of my test fleets getting astounding fuel economy. I could tract all the machines in my test fleet from wherever in the world I happened to be and when I plotted daily hours and fuel used this particular machine stood out so I sent one of my guys to check the operation. The contractor was short of operators so they had split operation of 2 machines, a dozer and a vibratory compactor, between one operator. He would start both machines at the beginning of the day, then use the dozer to move material, switch to the compactor to do its job, then back to the dozer never shutting an engine down during the day. Lots of idle time for both machines. When I sold my test machines I didn't get any more money for this one because of its easy life. I sold it based on the hour meter.

 

[Xfaxman]

The manual for my 2006 GMC Duramax says if more than one minute, shut it off. It starts so easy even in the Oklahoma winters, that I just use one battery, removed the second battery when it was new. Works for me.

 

[jimpen]

Well a story told to me by a trucker in the late 80's was that the company was b*****ing at them about leaving the tractors running overnight as they slept in New England winters. (Low temps and happy truckers don't match up.)

So one of the truckers, who was also a mechanic, rigged up a five gallon gas tank to the fuel line with pictures and everything and idled it overnight. It used about a half-gallon of diesel. The next night he reset the setup and stayed in a motel for the night. He went out in the morning and started it up. It took about 3/4 gallon of diesel to start it up.

He then made a package and sent it to to the dispatchers and several others up the chain. After that they were allowed to idle overnight.

Like I said this is a story heard in passing, way back when. Nothing to back it up, but it seemed believable at the time.

 

[David_Kb7uns]

The 2003 Ford 6.0L diesel I used to have would automatically kick up to a high idle when cold started. It would happen within 30 secs. to a minute after starting, and stay at high idle until the accelerator pedal was touched. My '11 Dodge Cummins with manual trans. doesn't do that, nor does it have a manual throttle control knob. I wish it did.

The 2005 Dodge Cummins had a high idle when below a certain temp, if you had an automatic transmission , not sure about the manual, you could go into the engine control computer and have the manual high idle enabled. For it to work had to be brake set, in park and you enabled and set cruise control buttons and used accel and decal buttons to change speed.

David Kb7uns

Did some more checking if you have a manual transmission you either need the clutch switch or grounding some pins an a harness depending on year for PTO applications.

 

[dave1949]

The 2005 Dodge Cummins had a high idle when below a certain temp, if you had an automatic transmission , not sure about the manual, you could go into the engine control computer and have the manual high idle enabled. For it to work had to be brake set, in park and you enabled and set cruise control buttons and used accel and decal buttons to change speed.

David Kb7uns

Did some more checking if you have a manual transmission you either need the clutch switch or grounding some pins an a harness depending on year for PTO applications.

Oh! I guess I wasn't curious enough. Thanks, I will check that out. Might even read the manual.

It's due for a state inspection, so if I can't find specifics, I could ask when it's at the dealer. It would be nice to be able to start it and let it warm up at high idle.

 

[john_bud]

Most of the extended idle mentality is from old way of thinking on old engines. Old diesels are a pain to start and easier to just let run... Stuff like pony start dozers, tractors and big trucks.

But new modern diesel don't benefit from sitting there idling for hours on end. But hey it your money ur sending up the stack so idle to your hearts content. If its gonna be more than 5 mins at idle I shut it off.

My old diesel tractor is a 1963. Just idling it will cool off and start to white smoke bad. Then after about 20 min it will slobber out the muffler as unburnt diesel mixed with exhaust soot is coming out. Takes about 5 min of hard work to heat up enough to stop smoking and another 15-20 to clean out the muffler.

Well a story told to me by a trucker in the late 80's was that the company was b*****ing at them about leaving the tractors running overnight as they slept in New England winters. (Low temps and happy truckers don't match up.)

So one of the truckers, who was also a mechanic, rigged up a five gallon gas tank to the fuel line with pictures and everything and idled it overnight. It used about a half-gallon of diesel. The next night he reset the setup and stayed in a motel for the night. He went out in the morning and started it up. It took about 3/4 gallon of diesel to start it up.

He then made a package and sent it to to the dispatchers and several others up the chain. After that they were allowed to idle overnight.

Like I said this is a story heard in passing, way back when. Nothing to back it up, but it seemed believable at the time.

Sorry, but this "story" is 100% total complete bs. Somebody sold you a bill of goods on it!
Just think about the start up you list. 3/4 of a gallon to start. It takes 1-3 sec of cranking to start a diesel engine when cold. If it's 3 seconds of cranking, it is pumping a quart of fuel per second. that's 60 quarts a minute or 15 gallon per hour. A typical gas pump runs 7 gal a min. A typical garden hose runs about 5 gal a min. The fuel injectors would have to put out a stream of fuel of truly heroic proportions. By the way, if it actually did put out that much fuel, the cylinders would hydrolock.

The idle consumption of a big diesel is also about a half gal per hour at low idle and up to 1.5 gal per hour at high idle. According to Cummins.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CDwQFjAD&url=http%3A%2F%2Fcumminsengines.com%2Fuploads%2Fdocs%2Fcummins_secrets_of_better_fuel_economy.pdf&ei=UO4wU8qWJoSNygGB1YG4Aw&usg=AFQjCNGuRpwrv1HIULfq3W0jHzsRph-wjA&bvm=bv.63587204,d.aWc

 

[sd455dan]

i let stuff idle all the time. i dont let the tractor idle for an hour for no reason, but i will idle 10 min, use for 5 min, idle for 10min, etc. its a utility diesel engine that uses negligable amounts of fuel to idle itself. i do not, and will never buy into the "cylinder washdown" theory, but people sure do love to throw that around. remember in the "old days" when equipment and trucks used to idle for hours and hours/days and days if necessary. i dont think there were too many 71 series detroits, 3406 cats, or even smaller equipment suffering from the terrible cylinder washdown. the things are made to run, and that is their only function in life. ideling is easy

yep - the guys running the train engines let those idle at the local switching area- sometimes for days and days....never saw any white smoke after all that time either...

 

[Jkott]

Well a story told to me by a trucker in the late 80's was that the company was b*****ing at them about leaving the tractors running overnight as they slept in New England winters. (Low temps and happy truckers don't match up.) So one of the truckers, who was also a mechanic, rigged up a five gallon gas tank to the fuel line with pictures and everything and idled it overnight. It used about a half-gallon of diesel. The next night he reset the setup and stayed in a motel for the night. He went out in the morning and started it up. It took about 3/4 gallon of diesel to start it up. He then made a package and sent it to to the dispatchers and several others up the chain. After that they were allowed to idle overnight. Like I said this is a story heard in passing, way back when. Nothing to back it up, but it seemed believable at the time.

It's beyond BS. My duramax can't idle for an hour on a half gallon of diesel. No way can a semi do it overnight. A half gallon of diesel has 64,000 btu of energy , assuming 100% efficiency. The electric block heater alone takes 34,000 btu to run for 12 hours (assuming the drivers off time) and it can barely keep the block warm, let alone the cab. There is no way it is physically possible to keep the engine running and warm, as well as heating the entire living quarters, with a half gallon of diesel. There is a reason that truck stops invented docking stations with power and heat/cooling. The smaller engine is simply in efficient at idle when compared to an electric power plant running in its efficient range.

Now if you told me it only burned all 5 gallons overnight, then I'd be impressed.

 

[RoyJackson]

yep - the guys running the train engines let those idle at the local switching area- sometimes for days and days....never saw any white smoke after all that time either...

I have read those locomotives are left idling (when they're not working) 24/7, 365 days a year, except for maintenance shutdowns.

 

[Tx Jim]

So one of the truckers, who was also a mechanic, rigged up a five gallon gas tank to the fuel line with pictures and everything and idled it overnight. It used about a half-gallon of diesel. The next night he reset the setup and stayed in a motel for the night. He went out in the morning and started it up. It took about 3/4 gallon of diesel to start it up.

REALLY only 1/2 gallon of fuel to ""idle the engine all night"" but 3/4 of a gallon just to start an cold engine???? I bet that trucker that performed that test was smoking some WACKY T-BACKY

 

[Blade Breaker]

Now with all this talk of diesel engines and extended idling no one has mentioned any failures or break downs because of idling. And would it make sense that "today's new engines" with the fuel injection technology compared to the old injection pumps would run much leaner at idle and have less tendency to have issues? I have had the same experience as john_bud on some older engines running rich or loading up when idling for a long time. Never any problems other than some smoke for a few minutes.
Everyone should do what they are comfortable with but I have a hard time believing that you could damage a diesel engine letting it idle.

 

[PapaPerk]

Now with all this talk of diesel engines and extended idling no one has mentioned any failures or break downs because of idling. And would it make sense that "today's new engines" with the fuel injection technology compared to the old injection pumps would run much leaner at idle and have less tendency to have issues? I have had the same experience as john_bud on some older engines running rich or loading up when idling for a long time. Never any problems other than some smoke for a few minutes.
Everyone should do what they are comfortable with but I have a hard time believing that you could damage a diesel engine letting it idle.

My Dodge Cummins manual says don't idle for extended time. I believe Cummins.

The engines will never warm up at idle in colder temps. Even with auto idle up mine will never reach operating temp idling.

 

[Blade Breaker]

My Dodge Cummins manual says don't idle for extended time. I believe Cummins.

The engines will never warm up at idle in colder temps. Even with auto idle up mine will never reach operating temp idling.

I believe cummins also. But I also am confident that it has more to do with the dpf filter than oil dilution or any other problems. The emissions is the big problem with "today's new engines".
Strange it does not warm up. My friends cummins is very good here in mn. Also my Ford warms up nicely idling.
I was only wondering if anyone has had any real problems with extended idling? Never heard of any myself.

 

[PapaPerk]

I believe cummins also. But I also am confident that it has more to do with the dpf filter than oil dilution or any other problems. The emissions is the big problem with "today's new engines". Strange it does not warm up. My friends cummins is very good here in mn. Also my Ford warms up nicely idling. I was only wondering if anyone has had any real problems with extended idling? Never heard of any myself.

What is dpf? Mine is a 2004.5. Only emission control it has is a cat.

 

[dave1949]

I believe cummins also. But I also am confident that it has more to do with the dpf filter than oil dilution or any other problems. The emissions is the big problem with "today's new engines".
Strange it does not warm up. My friends cummins is very good here in mn. Also my Ford warms up nicely idling.
I was only wondering if anyone has had any real problems with extended idling? Never heard of any myself.

Who's is going to idle their engine for long periods to see if they can cause a problem? Not me.

If habitual and lengthy slow idling shaved some, say 20%, life off of your engine, how would you know?