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Old 08-02-2018, 05:03 PM   #1
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Idling vs shutdown

Got a question for ISL/L9 owners. Curious to hear your thoughts.

I've noticed most big rigs leave their rigs running at the pump....

I can see a few reasons for this. One is to keep the turbo cooled with oil.. the other is to simply keep the cab cool/warm.... I'm guessing the turbo cooling is not much of a concern these days..

In general, it seems like most diesel rigs still favor idle over shut down. In fact I think most over the road trucks would typically idle all night while resting, but I think most have APUs these days.

Also, with DPFs... there is a totally new factor at play with passive vs active regens... and the DPF potentially clogging earlier with lots of idle time.

So, what do you do while fueling up (shutdown or idle)... How long do you idle while turning on the rear AC trying to cool things down.... My gut tells me to limit idle time. Maybe give it 2 minutes to cool things down before shutting it down after a hard pull.

I've heard that you can high idle with the cruise also, but I have not tired it yet.

I have not seen my temp gauge move yet. It seems to sit in the middle between 150 and 200 which I assume is about 180*. Even at 75mph on a 105* day... The fan clearly kicks in at time as it sounds totally different with RPMs, but don't really notice it at idle. Pretty happy with the way it runs so far. Just trying to learn more....
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Old 08-02-2018, 06:07 PM   #2
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I always let mine idle for awhile. When fueling up I use the truck pumps which usually means I have to go inside to pay, so I let the rig idle while going to pay but I then shut it off while pumping. I let my situation dictate how long I let the rig idle before shutting down, if I just finished pulling a long grade and pull into a rest area the rig is going to get a long idle time and the opposite if I drift down a long grade.
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Old 08-02-2018, 06:51 PM   #3
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I was taught by a pro years ago that by the time you've come off highway speeds down to city street speeds and pulled into the pump, you've allowed more than enough time to cool things down and you can shut it down at the pump. I've been doing that in motorhome with a C9 Cat engine and with an Cummins ISX with no problems at all.
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Old 08-02-2018, 07:04 PM   #4
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I totally agree with caseymyers, by the time you get to the fuel pumps the turbo has cooled down and ready to shut it down. With the DPF you want it to stay hot. I will shut my engine off in traffic if sitting and not moving for a long time. If I am going to be out of the Motorhome for a while and want to keep it cool or heated I will run the generator and AC.
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Old 08-02-2018, 08:45 PM   #5
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https://info.ornl.gov/sites/publicat...s/Pub61263.pdf

Freightliner Uses Cummins engines:

Excessive idle: Should be avoided when possible. Results in
reduced fuel economy and increased engine wear. An automatic
shutdown feature is available.
Fast idle: ISB (Interact System B) engines with the common rail
fuel system may automatically increase engine speed under cold
ambient conditions to decrease time for engine warmup under idling
conditions.
Engine warmup: Do not operate at full speed/load until coolant
temperature reaches normal operating range. Do not operate above
low idle until oil pressure is indicated.
Engine cooldown: Before shutdown, an engine should be idled 3–5
minutes after extended full throttle or high power operation.
However, under normal driving conditions, such as exiting a
highway, engine operation is generally lighter in nature and,
therefore, the 3–5 minute cooldown is not necessary

Internal combustion engines must not operate at low idle speed for
extended periods of time. This operating condition may lead to poor
engine performance. The idle shutdown feature, available on most
Cummins engines, can be programmed to shut the engine down
after a period of low idle speed operation with no driver activity. A
flashing warning lamp will inform the driver of an impending
shutdown. If an engine must idle for an extended period of time, it
should be done at fast idle (1,000 rpm or greater). The Power Take
Off (PTO) feature, available on most Cummins engines, can be
programmed to adjust engine speed with the use of OEM switches
to preprogrammed setpoints.
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Old 08-02-2018, 08:58 PM   #6
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https://cumminsengines.com/uploads/docs/4971288.pdf

Idle / Cooldown

Fast Idle
ISL engines with the common rail fuel system may
automatically increase engine speed under cold ambient
conditions to decrease time for engine warm-up under idling
conditions.

Engine Warm-up
Idling the engine for warm-up is not necessary. When oil
pressure is indicated, put motorhome in motion. Operate
with a light throttle and limited RPM until coolant temperature
reaches approximately 150ºF.

Engine Cooldown
Prior to shutdown, an engine should be idled 3-5 minutes
after extended full throttle or high power operation. However,
under normal driving conditions, such as exiting a highway,
engine operation is generally lighter in nature and thereby,
the 3-5 minute cooldown is not necessary.
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Old 08-03-2018, 12:48 AM   #7
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I let mine idle for a few minutes after first starting it and for a few minutes prior to shutting it off if I haven’t been driving slowly immediately beforehand. BUT I always use the high idle. Low idle is not good on these DEF/DPF engines.

Enable the cruise control, ‘set’ it, and ‘accelerate’ up to 1100 RPMs or so.
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Old 08-03-2018, 08:24 AM   #8
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I have had a Powerstroke diesel for 16 years. One of the things mentioned on my other forums regarding idle is a condition known as "wet stacking". The theory is that since diesels don't produce any power at idle they are running under the temperature needed to burn off excess fuel and this will run down the cylinder walls. Supposedly this is why the big trucks have high idle switches the prevent this sort of thing. True? I dunno. I read it on the Internet so it must be true.

On my new to me Cummins I use the cruise control and elevate the idle if I will be sitting for awhile.
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Old 08-03-2018, 11:27 AM   #9
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So the cruise control lets you set whatever idle speed you want? I'll have to play with it.

The shutdown makes sense in most cases.. but I would like to use the cab AC to assist in the coach cool down at times.

I'm curious why most over the road rigs seem to stay running at a decent idle speed while fueling up vs just shutting down. Maybe they are old enough to not have DPFs or there is some other reason.

Higher idle does not typically create load on an engine. I guess it's just that more heat in the exhaust helps keeps the passive regen going.
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Old 08-03-2018, 04:20 PM   #10
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To enable high idle ensure cruise control is set to on and hold up on the resume/accelerate dash lever and it will automatically go to high Idle about 1200 RPM... it will shut off automatically when you push on the brake
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Old 08-03-2018, 04:40 PM   #11
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Quote:
Originally Posted by LTZ470 View Post
To enable high idle ensure cruise control is set to on and hold up on the resume/accelerate dash lever and it will automatically go to high Idle about 1200 RPM... it will shut off automatically when you push on the brake
Thanks for clarification.
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Old 08-04-2018, 09:12 AM   #12
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" When fueling up I use the truck pumps which usually means I have to go inside to pay, so I let the rig idle while going to pay but I then shut it off while pumping."


Using "truck stop" fuel is usually 20c to 25c more costly than other diesel fuel.


Drive an extra 1/2 mile from the highway exit , and enjoy the extra $3.00 to $4.00 saved on the usual Sprinter 20G fill up.
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Old 08-04-2018, 10:15 AM   #13
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Join GoodSam and get their Swipe To Save card and you can go to Pilot/Flying J truck stops and swipe your payment CC first then the card and fill up. No going inside and a small discount also. Works great.
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Old 08-04-2018, 11:38 AM   #14
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Quote:
Originally Posted by FFred View Post
" When fueling up I use the truck pumps which usually means I have to go inside to pay, so I let the rig idle while going to pay but I then shut it off while pumping."


Using "truck stop" fuel is usually 20c to 25c more costly than other diesel fuel.


Drive an extra 1/2 mile from the highway exit , and enjoy the extra $3.00 to $4.00 saved on the usual Sprinter 20G fill up.
With having daul tanks, one on each side it makes filling up at anything other than a truck stop a pain. Truck stops have pumps on each side that are paired together so you can fill both tanks at once.
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Old 08-04-2018, 11:40 AM   #15
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Quote:
Originally Posted by hook47 View Post
Join GoodSam and get their Swipe To Save card and you can go to Pilot/Flying J truck stops and swipe your payment CC first then the card and fill up. No going inside and a small discount also. Works great.
I do have Good Sams but didn’t know about the Swipe to save card, Thanks
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Old 08-04-2018, 11:44 AM   #16
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Quote:
Originally Posted by Webefine View Post
I do have Good Sams but didn’t know about the Swipe to save card, Thanks
go to rvpluscard.com and sign up.

I use it all the time. After fueling I take picture with my phone for a receipt.

Never go in the store unless we need some food or drink.
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Old 08-04-2018, 12:47 PM   #17
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Truck pumps make the most sense for a saddle tank DX3. Pull in, fuel up, and get gone. I haven't had to go inside to pay for fuel...yet.
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Old 08-04-2018, 03:47 PM   #18
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Quote:
Originally Posted by hook47 View Post
Join GoodSam and get their Swipe To Save card and you can go to Pilot/Flying J truck stops and swipe your payment CC first then the card and fill up. No going inside and a small discount also. Works great.
Only prob with this is it only pre auths for $75 usually. Chase will sometimes let me swipe a second time but never a third without a fraud alert. Easier to just go in and pre auth for 250-300

Truck stops are a necessary evil with the convenience of double pumps and bulk DEF. I do try and find the mom and pop ones in between DEF fills to save a few bucks
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Old 08-04-2018, 07:16 PM   #19
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Haven't had that dollar limit problem yet.
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