Base Idle, Fast Idle, Non Idle - Best Practices Diesel

supercub wrote:
I talked to a trucker and he said the only time he turns the engine off is when he's having it serviced. Truckers idle them over night all the time. What's the difference?? Thanks
Brian

No difference-- it is not good for their engines either.

Why is it not a good idea to idle a DP engines when diesel trucks idle for hours. I talked to a trucker and he said the only time he turns the engine off is when he's having it serviced. Truckers idle them over night all the time. What's the difference?? Thanks
Brian

I believe much of the high idle thinking is left over from the olden days of diesel. these new computer controlled engine are smarter than many who operate them.

I see no valid reason to fix some thing which isn't broke.

Or should I fix it until it is?

"holstein13"......The reason "Mr.Mark" stated that he waits a minute before engaging high idle, is to allow the oil to get circulated through the engine. You don't want to go from a cold start to half throttle.

On older coaches, probably 2007-2008 and older, you could adjust the base idle from the Smart Wheel. You could adjust it up or down in 25rpm increments with the cruise. I mention this, because it's easy to lower the idle accidentally without realizing.

lc0338 wrote:
Here is information from my 2014 Ram 5500 owners manual about high idle feature (Automatic transmission only)

* The Idle-up feature uses the speed control switches to increase engine idle speed and quickly warm the vehicle's interior. This feature must be enabled by your dealer. See your local dealer.
* With the transmission in PARK, the parking brake applied, and the engine running, push the speed control ON/OFF switch to on, then push the set button.
* The engine RPM will go up to 1100 rpm. To increase the RPM, push and hold the RESUME/ACCEL button and the idle speed will increase to approximately 1500 RPM. To decrease the RPM, push and hold the SET/DECEL button and the idle speed will decrease to approximately 1100 RPM.
* To cancel the idle-up feature, either push the cancel switch, push the ON/OFF switch or push the brake pedal.

My high idle is activated and my tranny also has a PTO so I suppose that 1100 RPM is adequate for making sure the excess fuel gets burned off and the availability to increase RPM to 1500 RPM is to support the PTO and it's use.

Here is what the manual says about engine idling:

Avoid prolonged engine 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, engine valves, and injector nozzles. Also, the unburned fuel can enter the crankcase diluting the oil and causing rapid wear to the engine.

If the engine is allowed to idle, under some conditions the idle speed may increase to 900 RPM then return to normal idle speed. This is normal operation.

Thanks, that's great information. Maybe I'll set my high idle to 1100.

holstein13 wrote:

lc0338 wrote:
Picked this off a diesel forum:

The purpose for high idle is to avoid a condition called wet stacking. An engine at idle does not create high enough cylinder temps to atomize the entire amount of fuel being injected into each cylinder causing the unburned fuel to mix with, and wash down the oil from the cylinder wall, thus dilluting the engine oil with diesel fuel and causing excessive engine wear. All class 8 and 6 engines have had the ability to raise the idle through the use of the cruise control since their conversion to electronic engine controls, and most manufacurers recomend a minimum of 1,000 rpm for extended or prolonged engine idle periods. On my 06 automatic truck, when the temps are low enough it will idle up to 1000 rpm after 3 minutes at base idle, or I can engage the high idle by pressing the cruise button on then pressing the resume/set side, it will instantly jump to 1,100 rpm, if I continue to hold the resume/set button the engine rpm will continue to rise to 1,500 rpm and stay there until I disengage the cruise with the on/off button, or step on the brake.

This looks very interesting and plausible. So the real question is how high of an idle is high enough? And does it make a difference in our application?

Here is information from my 2014 Ram 5500 owners manual about high idle feature (Automatic transmission only)

* The Idle-up feature uses the speed control switches to increase engine idle speed and quickly warm the vehicle's interior. This feature must be enabled by your dealer. See your local dealer.
* With the transmission in PARK, the parking brake applied, and the engine running, push the speed control ON/OFF switch to on, then push the set button.
* The engine RPM will go up to 1100 rpm. To increase the RPM, push and hold the RESUME/ACCEL button and the idle speed will increase to approximately 1500 RPM. To decrease the RPM, push and hold the SET/DECEL button and the idle speed will decrease to approximately 1100 RPM.
* To cancel the idle-up feature, either push the cancel switch, push the ON/OFF switch or push the brake pedal.

My high idle is activated and my tranny also has a PTO so I suppose that 1100 RPM is adequate for making sure the excess fuel gets burned off and the availability to increase RPM to 1500 RPM is to support the PTO and it's use.

Here is what the manual says about engine idling:

Avoid prolonged engine 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, engine valves, and injector nozzles. Also, the unburned fuel can enter the crankcase diluting the oil and causing rapid wear to the engine.

If the engine is allowed to idle, under some conditions the idle speed may increase to 900 RPM then return to normal idle speed. This is normal operation.

Tom/Barb wrote:
My cruise control will not set high idle, thus, I never use it.

Tom/Barb, you may be able to enable this feature. To use it, you must download PowerSpec directly from Cummins and enable the "PTO Feature." Alternatively, you can stop by a Cummins distributor and they can plug in and enable it.

I know you are asking yourself what the PTO has to do with our coaches since we technically don't have a PTO but that's what's connected to your cruise control when you are in neutral. By hitting either the set or resume button if the PTO Feature is turned on, it will set the engine to the minimum RPM set in the PTO section of your engine parameters.

Ozlander wrote:

holstein13 wrote:
Otherwise, I'll high idle (1,000 RPMs) or turn off the ignition (preferred).

I'm surprised you have an ignition switch on your diesel.
What is it's purpose?

Now you're picking nits. What I'm calling the ignition switch is the starter switch. It has a key in it and I use it to turn off and on the engine. It's not really an ignition system, per se. Although ignition does occur.

My cruise control will not set high idle, thus, I never use it.

holstein13 wrote:
Otherwise, I'll high idle (1,000 RPMs) or turn off the ignition (preferred).

I'm surprised you have an ignition switch on your diesel.
What is it's purpose?