Idling Diesel Really Bad?
- Thread starter Cyprs
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is that good or bad.
I have always let my camper van (former 91' ambulance with an International 7.3L diesel) idle with the high-idle switch on. I assumed that it was better for the engine. I also use the shore line to plug in the block heater for a few hours before I start it. I hope this a good routine.
Don't pick on the ambulance guys. They need to kick up the idle to keep the lights going and the box warm /cool . We never know how long we might be out on a call.
It's a shame Doug Hillary isn't posting on here anymore, he'd take you to task on that one
Lets just say he's very anti idling any diesel, he's a consultant to the industry here, and runs his own fleet.
IIRC, his drivers were instructed to idle never more than 1.5-2 minutes maximum.
I wanted to know so I asked Cummins...here's their answer.
Thanks Cummins!
Extended cold weather idling
Solution:
We publish and state some simple guidelines, but we have no official policy for diesel engine idling. Basically, engines are made to work and not idle. Excessive idle shortens oil drain intervals, is classified as "severe duty" service, and - under the worst of conditions - can lead to engine damage.
One issue with excessive idling is injector carboning which can lead to premature failure or increased injector maintenance. Excessive idling can also cause carbon build up on pistons and piston rings, which can lead to excess oil consumption.
Anything more than 30-40% idle is considered severe duty service, but how that percent idle is attained may be worse than severe. We generally don't like to see engines idled for more than 10 minutes. If the idle speed is increased to 1,100 -1,200 rpm then internal engine temperatures are warm enough to prevent the worst case damage and also pollute the air less.
Low oil sump temperatures, combined with low ambient air temps and low speed idle cause incomplete combustion, producing sludge, carbon deposits on injectors and internal engine components, weak organic acids in the oil - and, ultimately lead to valve sticking and bent pushtubes/pushrods.
There are options. Idling up the RPM as stated above is one. "Smart" systems which turn the engine off/on (while maintaining adequate coolant temperature) are another. Cummins has a system called ICON which does just that. Sometimes though, the engine needs to run - not just for the comfort, but for the safety of the operator. Arctic operations are an example.
Generally, people have held the traditional belief that diesels should just "hammer away" at idle, and this is sort of a "diesel thing." This is an old belief that needs to be dispelled. Operators and drivers prefer to keep the engine running for warmth in the winter and for A/C in the summer. Actual idle times are higher than one would expect, except for disciplined fleets which either reward for low idle times or provide other incentives.
In past studies, Cummins has determined that low speed idle can contaminate the oil at between 1-1/2 to over twice the normal rate; this is one of the main reasons for recommending "severe duty" maintenance intervals for engines operating with more than 40% idle time. Another reason is that, if sump temperatures are not sufficiently high, the water (produced by combustion, let alone condensation) will not be heated enough to evaporate from the oil.
In the Dodge/Ram Cummins midrange engine application, both Dodge and Cummins have recommended owners to limit idle time to 5 minutes and have also offered a software upgrade "idle up" feature, which increases the idle speed, warming up the engine enough to limit incomplete combustion byproducts.
There may be some balance in stop-and-go driving and urban delivery, wherein one would trade off the benefits to be gained from reducing idle time against the fact that shutting the engine down (every time it's not pulling a load) necessarily creates a "starting event." If the "off time" is long enough, there is a transient starting event time where the oil pressure is not fully established and the engine is running. Accelerated wear can occur during these conditions. In hot temperatures, when the oil is thinner, the oil drains away quickly so some degree of idle may be preferred to starting/stopping and restating the engine fifty times a day.
Common sense may be the best guideline. Common sense would include an appreciation of the above and factor in outside temperature, whether or not the engine will be run for a long enough time later in the day (to burn off carbon and water), how long the idle is, whether or not the A/C needs to be run, etc. Again, one of the parameters defining "severe duty" is excessive idle time; running at idle for more than ten (10) minutes probably doesn't make sense; the "smart idle" ICON-type devices will help; balancing the cost of excessive idle vs. the utility/necessity/option of idle, etc.... all of these considerations should be factored in.
We thank you for your interest in Cummins products. Please let us know if you need assistance in locating the nearest Cummins-authorized Dealer or Distributor Service Provider. For assistance in locating a Service Provider, feel free to use Cummins North America Dealer Locator, which can be found on Cummins website:
Thanks Cummins!
Extended cold weather idling
Solution:
We publish and state some simple guidelines, but we have no official policy for diesel engine idling. Basically, engines are made to work and not idle. Excessive idle shortens oil drain intervals, is classified as "severe duty" service, and - under the worst of conditions - can lead to engine damage.
One issue with excessive idling is injector carboning which can lead to premature failure or increased injector maintenance. Excessive idling can also cause carbon build up on pistons and piston rings, which can lead to excess oil consumption.
Anything more than 30-40% idle is considered severe duty service, but how that percent idle is attained may be worse than severe. We generally don't like to see engines idled for more than 10 minutes. If the idle speed is increased to 1,100 -1,200 rpm then internal engine temperatures are warm enough to prevent the worst case damage and also pollute the air less.
Low oil sump temperatures, combined with low ambient air temps and low speed idle cause incomplete combustion, producing sludge, carbon deposits on injectors and internal engine components, weak organic acids in the oil - and, ultimately lead to valve sticking and bent pushtubes/pushrods.
There are options. Idling up the RPM as stated above is one. "Smart" systems which turn the engine off/on (while maintaining adequate coolant temperature) are another. Cummins has a system called ICON which does just that. Sometimes though, the engine needs to run - not just for the comfort, but for the safety of the operator. Arctic operations are an example.
Generally, people have held the traditional belief that diesels should just "hammer away" at idle, and this is sort of a "diesel thing." This is an old belief that needs to be dispelled. Operators and drivers prefer to keep the engine running for warmth in the winter and for A/C in the summer. Actual idle times are higher than one would expect, except for disciplined fleets which either reward for low idle times or provide other incentives.
In past studies, Cummins has determined that low speed idle can contaminate the oil at between 1-1/2 to over twice the normal rate; this is one of the main reasons for recommending "severe duty" maintenance intervals for engines operating with more than 40% idle time. Another reason is that, if sump temperatures are not sufficiently high, the water (produced by combustion, let alone condensation) will not be heated enough to evaporate from the oil.
In the Dodge/Ram Cummins midrange engine application, both Dodge and Cummins have recommended owners to limit idle time to 5 minutes and have also offered a software upgrade "idle up" feature, which increases the idle speed, warming up the engine enough to limit incomplete combustion byproducts.
There may be some balance in stop-and-go driving and urban delivery, wherein one would trade off the benefits to be gained from reducing idle time against the fact that shutting the engine down (every time it's not pulling a load) necessarily creates a "starting event." If the "off time" is long enough, there is a transient starting event time where the oil pressure is not fully established and the engine is running. Accelerated wear can occur during these conditions. In hot temperatures, when the oil is thinner, the oil drains away quickly so some degree of idle may be preferred to starting/stopping and restating the engine fifty times a day.
Common sense may be the best guideline. Common sense would include an appreciation of the above and factor in outside temperature, whether or not the engine will be run for a long enough time later in the day (to burn off carbon and water), how long the idle is, whether or not the A/C needs to be run, etc. Again, one of the parameters defining "severe duty" is excessive idle time; running at idle for more than ten (10) minutes probably doesn't make sense; the "smart idle" ICON-type devices will help; balancing the cost of excessive idle vs. the utility/necessity/option of idle, etc.... all of these considerations should be factored in.
We thank you for your interest in Cummins products. Please let us know if you need assistance in locating the nearest Cummins-authorized Dealer or Distributor Service Provider. For assistance in locating a Service Provider, feel free to use Cummins North America Dealer Locator, which can be found on Cummins website:
Current reports from two of the diesel OEM find that idling more than five minutes is detrimental to engine life. One hour of idling was found to be the equivalent of 90 to 105 miles of normal load operation at posted speed limits. Inadequate oil pressure/flow to areas in the engine as well as overcooling of cylinder liners and heads caused fuel dilution to lube oil and inadequate/incomplete combustion, leading to coking of injector tips, exhaust valves and turbocharger turbines.
These are some interesting comments! I remember reading (back in the middle 1960s) how OTR freight companies starting to use oil analysis to determine maint intervals and such. In the engines (gas or diesel, I don't remember) they let run while the drivers went in to get something to eat, less fuel dilution and longer engine life. A significant enough difference that they started using the "leave it running" orientation rather than otherwise. The maint savings paid for the added fuel use, easily.
It appears that many of these comments are from the cold climate areas too, rather than more temperate. Plus industrial than consumer uses, in many cases, which can have a different use orientation in some cases.
Considering that diesels are generally "throttle-less", being compression-fire engines throttled by the amount of fuel they receive, I find the "fuel washing" issues quite interesting. I really suspect the stuff running down the stacks would not be unburned fuel, but condensate plus "soot" combined. Just a hunch.
If "fuel washing" is a new, emerging issue, I would suspect that current oil standards are addressing that issue? Not to mention a huge decrease in engine life. Seems a little strange, on the surface, that with all of the computerized engine management controls, this is an issue at all--especially in a more emissions-sensitive era we now live in.
I also wonder how much the new lower-sulphur fuels are or can affect these situations (i.e., sticking of whatever)? From looking at the numbers, the sulphur content was not great to start with, but now is lower.
On OTR transit busses, the "high idle" has been around for ages. Not sure if it's due to the additional load the a/c and electrical systems see when the vehicle is being loaded/unloaded for passengers and luggage, or if it really did have something to do with other items in those earlier times.
From my own experiences with the earlier GM diesel pickups, I would leave them running (and locked) during short stops I made. It kept the a/c head pressure under control and I had normal power when I got back into them to leave--otherwise, there was too much load from getting the a/c back up to speed, on the engine's meager power.
On another issue related to diesel idling, it relates to exhaust emissions. Many truckstops in the south have now set up docking stations for the trucker's use overnight. Many cities/states now have ordinances against idling diesel/gas engines for more than 30 minutes. The dock station supplies a/c, electric power, internet, etc. via one of the cab's windows--for a fee.
I wonder if the new directives of "no idle periods", with related service issues, might be a side-way of the manufacturers getting customers/users to decrease their vehicle's idle time to decrease exhaust emissions concerns? Kind of like manufacturers specing 5W30 or 10W30 engine oils in engines that used to exist on other viscosities of oils in prior times? A hidden agenda of sorts?
Again, I find some of these comments and orientations interesting considering how things were not that long ago.
Curiously,
CBODY67
It appears that many of these comments are from the cold climate areas too, rather than more temperate. Plus industrial than consumer uses, in many cases, which can have a different use orientation in some cases.
Considering that diesels are generally "throttle-less", being compression-fire engines throttled by the amount of fuel they receive, I find the "fuel washing" issues quite interesting. I really suspect the stuff running down the stacks would not be unburned fuel, but condensate plus "soot" combined. Just a hunch.
If "fuel washing" is a new, emerging issue, I would suspect that current oil standards are addressing that issue? Not to mention a huge decrease in engine life. Seems a little strange, on the surface, that with all of the computerized engine management controls, this is an issue at all--especially in a more emissions-sensitive era we now live in.
I also wonder how much the new lower-sulphur fuels are or can affect these situations (i.e., sticking of whatever)? From looking at the numbers, the sulphur content was not great to start with, but now is lower.
On OTR transit busses, the "high idle" has been around for ages. Not sure if it's due to the additional load the a/c and electrical systems see when the vehicle is being loaded/unloaded for passengers and luggage, or if it really did have something to do with other items in those earlier times.
From my own experiences with the earlier GM diesel pickups, I would leave them running (and locked) during short stops I made. It kept the a/c head pressure under control and I had normal power when I got back into them to leave--otherwise, there was too much load from getting the a/c back up to speed, on the engine's meager power.
On another issue related to diesel idling, it relates to exhaust emissions. Many truckstops in the south have now set up docking stations for the trucker's use overnight. Many cities/states now have ordinances against idling diesel/gas engines for more than 30 minutes. The dock station supplies a/c, electric power, internet, etc. via one of the cab's windows--for a fee.
I wonder if the new directives of "no idle periods", with related service issues, might be a side-way of the manufacturers getting customers/users to decrease their vehicle's idle time to decrease exhaust emissions concerns? Kind of like manufacturers specing 5W30 or 10W30 engine oils in engines that used to exist on other viscosities of oils in prior times? A hidden agenda of sorts?
Again, I find some of these comments and orientations interesting considering how things were not that long ago.
Curiously,
CBODY67
Most diesels don’t produce much moisture compared to a gas engine. There is a lot of soot on the stacks, but the soot will be all around the top of the stack and never more than about 6 inches down from the top. The long streaks that you may see is fuel slobber (which may be the result of long periods of hard desecnt with the Jakes on as well as idling). White smoke in a diesel, especially if the truck has been run for a while, is un-burnt fuel (as opposed to soot producing partially burned fuel which is black smoke).
Washing down the cylinders is not a new, in fact it is not nearly as common as it was with mechanical diesels of years gone by. It still happens, but excessive idle time takes much longer to show up in modern engines. Today’s diesels have excellent fuel management, plus the materials, machining and oils are much better which all tolerate severe duty much better.
Most buses, transit or motorcoach, have a high idle feature to keep the batteries charged and the heater/A/C working. Buses have a lot of lights and other electronics that you don’ see that have to be powered up. Most buses have some version of a Delco oil cooled 300 amp alternators that needs about 1000-1200rpm of engine speed to keep up with demand. More compact air-cooler alternators are starting to make an appearance in these markets, but it’ll be some time before we see how they stack up to the old Delco’s.
Certainly some laws and company policies have mandated lower idle times. This is mostly an emissions concern. One shouldn’t go to extremes when talking about idle time. A short time ago idle time was dictated by service concerns and myth. Now they are concerned with emissions and fuel consumption. If you talk to any competent, qualified diesel mechanic that has been in the field for any length of time they will tell a story similar to mine and regale you of stores from the “old days” when idle related failures where more common place.
Washing down the cylinders is not a new, in fact it is not nearly as common as it was with mechanical diesels of years gone by. It still happens, but excessive idle time takes much longer to show up in modern engines. Today’s diesels have excellent fuel management, plus the materials, machining and oils are much better which all tolerate severe duty much better.
Most buses, transit or motorcoach, have a high idle feature to keep the batteries charged and the heater/A/C working. Buses have a lot of lights and other electronics that you don’ see that have to be powered up. Most buses have some version of a Delco oil cooled 300 amp alternators that needs about 1000-1200rpm of engine speed to keep up with demand. More compact air-cooler alternators are starting to make an appearance in these markets, but it’ll be some time before we see how they stack up to the old Delco’s.
Certainly some laws and company policies have mandated lower idle times. This is mostly an emissions concern. One shouldn’t go to extremes when talking about idle time. A short time ago idle time was dictated by service concerns and myth. Now they are concerned with emissions and fuel consumption. If you talk to any competent, qualified diesel mechanic that has been in the field for any length of time they will tell a story similar to mine and regale you of stores from the “old days” when idle related failures where more common place.
Why not design a diesel engine that can shut off some of the injectors while idling? Instead of running on six cylinders, let it run on three holes. This would work those cylinders harder and raise the combustion temps, let the other cylinders act like air compressors to help maintain heat. This should be easy to do with modern computer controls. Raise the idle speed and shut off half of the engine. Just perfect for those emergency vehicles that really need to keep idling.
Joe
Joe
Like this?
http://www.wagnerandassociates.biz/smarty.htm
Marco and Bob Wagner have created one heck of a program with the Smarty.. I'm saving the change under my sofa right now for one.. Can't wait to use it in person!
http://www.wagnerandassociates.biz/smarty.htm
Marco and Bob Wagner have created one heck of a program with the Smarty.. I'm saving the change under my sofa right now for one.. Can't wait to use it in person!
when you go to a rest stop i the interstate, notice that just about every single truck there is idling while the operators are sleeping in the back.
hardly anyone who uses a diesel commercally shuts them down except for refueling or some other such need.
hardly anyone who uses a diesel commercally shuts them down except for refueling or some other such need.
That doesn't make it good for the engine though.
Hammer
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