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Idling vs restarting an EcoDiesel

16K views 29 replies 15 participants last post by  Tinman2 
#1 ·
I'm sure many of us have pondered the tradeoffs between stopping/restarting our engines as opposed to just letting the diesel idle in the parking lot while we run some quick errands.

There must be an estimated duration where it would be better to shutdown/restart as opposed to idling. I'm sure that this duration is further extended for GDE tune users, due to their algorithm that reduces soot production. For the sake of discussion let's presume the cost of diesel consumption at idle is de minimis and we are concerned only with long-term engine health.

What rules of thumb do other people use?
 
#3 · (Edited)
I thought it said to avoid idling it for extended periods.
Good point.

Engine Idling
Avoid prolonged idling, long periods of idling may be harmful to your engine because combustion chamber temperatures can drop so low that the fuel may not burn completely. Incomplete combustion allows carbon and varnish to form on piston rings, cylinder head valves, and injector nozzles. Also, the unburned fuel can enter the crankcase, diluting the oil and causing rapid wear to the engine.

...and then in the next breath they talk about when you *should* idle the engine for a while (heh).

I wonder if EGT is a reasonable proxy for combustion chamber temperature.

Presumably this low combustion chamber temp scenario isn't applicable to GDE tune users with high idle, when it's currently active—though this isn't the end-user reason for that optional feature.

I suppose if these EcoDiesels ever get a stop-start added with no salient mechanical changes then the debate about whether the engine should be stopped for quick errands will take a turn.
 
#4 ·
I can only offer antidotal information from the 189000 miles I put on my SuperDuty.
I never let it idle this isn't some huge Cat engine that needed to do so. Fuel consumption was 1 oz per minute or about a gallon an hour.
Never a starter issue doing this and never a problem.

I don't see any point in letting any diesel idle unless super cold where restart could be an issue. Cold stacking is very possible in cold climates doing this because the engine isn't under load...


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#5 ·
I can only offer antidotal information from the 189000 miles I put on my SuperDuty.
I never let it idle this isn't some huge Cat engine that needed to do so. Fuel consumption was 1 oz per minute or about a gallon an hour.
Never a starter issue doing this and never a problem.
Seems to be good advice.

I don't see any point in letting any diesel idle unless super cold where restart could be an issue. Cold stacking is very possible in cold climates doing this because the engine isn't under load...
Definitely. Too bad the stock firmware doesn't have a high idle condition to prevent this... something the GDE tune offers an option.
 
#6 ·
I'll idle until oil temp drops to 208F and then turn it off. If the oil temp is already 208F or less, I'll turn it off when I expect to idle 10 seconds or more when safely parked or waiting at a drive through.

The 10 second rule is just some advice gleaned from a hypermiler forum. It was for gassers, but I imagine this small displacement diesel to be similar.

Safety > comfort > economy. If it's unsafe or too hot/cold to be comfortable with the engine turned off, leave it running.
 
#17 ·
I'll idle until oil temp drops to 208F and then turn it off. If the oil temp is already 208F or less, I'll turn it off when I expect to idle 10 seconds or more when safely parked or waiting at a drive through.



The 10 second rule is just some advice gleaned from a hypermiler forum. It was for gassers, but I imagine this small displacement diesel to be similar.



Safety > comfort > economy. If it's unsafe or too hot/cold to be comfortable with the engine turned off, leave it running.


Where does that number come from, the 208 °F?


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#7 ·
Is that a real oil temp? On the Cummins it's calculated, not real, no sensor. Event the oil pressure gauge on the older Cummins isn't real, just a glorified idiot light. I don't trust OEM gauges not one little bit.
 
#8 ·
I suppose it depends on how you define "real". As I understand it, the temperature sensor is on the outlet of the oil cooler just before the oil goes back to circulation. So, it is "real", but I don't know that I'd consider it "true" since the oil temperature would be higher almost everywhere else in the system, especially near the turbo.

Really, I don't care if it's real. It could read 0 or 1, as long as 0 means safe to turn off and 1 means idle until 0.

It serves the purpose and seems to move in a realistic fashion. When it's super hot outside and I've been driving hard, it takes a long time to cool down, as you'd expect, and conversely for the opposite conditions, as you'd expect.
 
#10 ·
Unless it's really hot outside and, I'll turn off the ignition when I know I will be waiting more than a couple of minutes like when I'm waiting for a mile-long train to go by at 20 MPH. :)

Two minutes of no AC in the summer sun is worse than 2 minutes of no heat at -20°F when you are wearing a winter coat and warm socks.
 
#11 ·
Unless it's really hot outside and, I'll turn off the ignition when I know I will be waiting more than a couple of minutes like when I'm waiting for a mile-long train to go by at 20 MPH. :)

Two minutes of no AC in the summer sun is worse than 2 minutes of no heat at -20°F when you are wearing a winter coat and warm socks.
The way I look at it, any Vehicle I own better be able to take care of me regardless of any external conditions...whether it is 95 Deg out or -15 deg out. If I want or need it to Idle for 30 min waiting to pick some one up etc, then I surely hope it can be able to do that with no adverse effects on the unit. That's all part of what product testing and engineering is for....:cool:
 
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#13 ·
Brought my jeep to the dealership this week for an oil leak, and the next day I get call saying they added a dye to try and find the leak and let it idle for an hour :mad:. It's a slow leak so nothing showed up and I'm driving it around for a few days before bringing it back.

Anything that can be done to help reverse any damage they may have done by letting it idle for so long when the engine was cool to start?
 
#14 ·
... and let it idle for an hour...

Anything that can be done to help reverse any damage they may have done by letting it idle for so long when the engine was cool to start?
Shouldn't be any damage. Some guys idle their ecodiesel for the whole time they sleep at rest stops (4+ hours) with no ill effect.

As I understand it, our engines have plenty of oil pressure at idle and the EGR system is off at idle. Those are really the only two things to worry about with idling and our engines do fine on both counts.
 
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#16 ·
But the GDE high idle only works under 36* ambient temps.
That's correct. The post you quoted was discussing idling in cold environments... and really, that's the condition one might *need* to idle rather than shutting down.

If you wish to explore obtaining high idle all the time, you might contact GDE to see what they say. They do respond to customer feedback.
 
#18 ·
Interesting discussion. The GCED on order is replacing a Dodge Cummins work truck with just short of 1 million miles. Over its life this truck has seen more than its share of idling. In the summer it gets started in the morning and never gets shut off all day to keet the a/c running. In the fall/winter its the same routine for cab heat. I am constantly in and out of the truck and its nice to climb into a warm/cool cab.

Never experienced any engine problems, just a bit more fuel consumed. Dont plan on changing my routine on the ED.
 
#25 ·
On my Super Duty Ford has a kit that is plug and play. I could adjust the idle at whatever rpms I wished just to make sure that you would not wet stack the engine. I think this diesel doesn't have that issue since wet stacking is caused by the engine getting too cold idling and not under a load...
 
#26 ·
Illegal to idle is Texas?? Why in the world. If we are traveling with the dogs, I do this often (with the truck locked - I have a non-ignition key just for this task). Can't leave the kids in a hot truck while stopped to eat.

The high idle feature on the Cummins (stated above) is really handy for the duty. I use it a lot for A/C, cold starts, etc. I have a external plug and play device on my 01 that works the same way. I use to run the engine driven air compressor - very nice.

BD Diesel sells a plug and play module for the ED 1500 truck that is similar. Can adjust idle to 1500rpm IIRC. About $240. In general: Don't idle a modern diesel. But if you need to, this is the way to go.
 
#29 ·
Thank you, f2d. I saw 'wet stacking' above in this thread and didn't know what it meant. And I was too busy at that time to search it. Thank you for providing that link and for explaining about the idling.

<RANT ON>
The Jeep owner manual requirement to not idle the JGC CRD for 'an extended period of time', or words to that effect, is not really a requirement. Reason: define "extended". Is that 5 minutes or 5 hours or 5 days?

I posted upthread that when I was in the military and drove HummVees and 5-tons I was told you could idle the engines all day. In fact when we were 300 miles north of the Arctic Circle in Norway in the dead of winter, we kept the trucks idling all night long.

So again, Jeep, what is "extended"? Some guidelines to help define that would help.
<RANT OFF>

And also the info in this thread does help, so thanks again f2d, and the others who have chimed in with their experience and shared their knowledge.
 
#30 ·
Extended Idling any common rail is bad because combustion chamber temperature is so low and wet stacking can occur. Extended idling in a modern DPF/SCR engine is much worse b/o all that crap needs heat to make it work and stay clean. Don't do it. That said, some of the newer models are better depending on hardware. The newer Cummins will shut down the nozzle on the turbo (exhaust brake effect) and some other stuff that makes it much better. IMHO if you need to idle over 5-10 minutes get an external device to rev it up.
 
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