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

I agree you should not idle longer than necessary BUT when I have to for putting the slides in or out and building up air pressure to leave, I click it up to 1000 rpm.

Several good things happen. Your oil pressure goes up, alternator, compressor and ac compressor spin faster and it helps bring engine temp up.

I dont kick it up at redlights.

The computers control everything in the engines now. The injectors are no longer mechanical or pump timed, they are piezo-electric and the computer tells it how much and how long to emit fuel. Stacking is no longer much of a problem with the new systems and they (the manufacturers) recommend no warmup or no idle down to shutoff. Diesel engines at low idle tend to cool below desirable operating temps so they program in a high idle at 1200 rpm and a pto idle at 1500 rpm. The high idle will keep the temperature high enough to circulate oil as needed.

Turn on the cruise control, hit 'set' for high idle. 'resume' for pto idle.

Diesel engines wear the most when starting them up. The seconds after startup when there is no oil pressure can starve bearings and cause premature wear. That is precisely why leaving the engine running when stopped for short periods is recommended and using high idle.

How many have read the Operators manual on 2010 models and newer? The days of extended idle periods are over. No more than 10 min. Idling especially diesels uses a lot of air (oxygen), pollutes, uses nonrenewable energy. Idling diesels are noisy. Reduces MPG too.
I shut mine off even for a min or two.

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?

Busskipper wrote:

holstein13 wrote:
What are best practices for idling and what are the theories behind them. For example, I never use my base idle speed unless I'm in traffic or at a red light. Otherwise, I'll high idle (1,000 RPMs) or turn off the ignition (preferred).

Is the high idle at startup to charge the batteries? or is it to get the engine to operating temperatures faster? And does it really matter at all given how little we actually use our engines in a diesel RV?

IMHO - the high idle is just that a high idle - allows you to idle at 1,000 rpm's without having to sit in the seat and put your FOOT on the pedal.

The new engine has a computer that is much smarter than you or I - it is designed to allow these engines to run better and longer - don't try to over think it, just drive it and enjoy it. These same engines are used in all sorts of commercial applications with NO REGARD for the engine, or it's life. I've known commercial engines to "survive" for 10,000 hours of run-time on one oil change - not that it did it any good but after 10,000 hours of run time it still had oil pressure and still preformed like all normal diesels, doing it's job.

My Guess is that when you and I are gone, both of our engines (DIESELS) will still have a lot more life in them.

Relax and enjoy the Coach,

JMHO,

Unfortunately, my computer won't engage the high idle automatically, nor will it turn off the ignition. My engine purrs at base idle until I actively force it to high idle or turn off the ignition. My computer may be smarter than me, but it won't manage the idle speed without my input.

But maybe it doesn't even matter. As you wrote, these engines will take abuse and last a very long time almost no matter what we do to them.

holstein13 wrote:
What are best practices for idling and what are the theories behind them. For example, I never use my base idle speed unless I'm in traffic or at a red light. Otherwise, I'll high idle (1,000 RPMs) or turn off the ignition (preferred).

Is the high idle at startup to charge the batteries? or is it to get the engine to operating temperatures faster? And does it really matter at all given how little we actually use our engines in a diesel RV?

IMHO - the high idle is just that a high idle - allows you to idle at 1,000 rpm's without having to sit in the seat and put your FOOT on the pedal.

The new engine has a computer that is much smarter than you or I - it is designed to allow these engines to run better and longer - don't try to over think it, just drive it and enjoy it. These same engines are used in all sorts of commercial applications with NO REGARD for the engine, or it's life. I've known commercial engines to "survive" for 10,000 hours of run-time on one oil change - not that it did it any good but after 10,000 hours of run time it still had oil pressure and still preformed like all normal diesels, doing it's job.

My Guess is that when you and I are gone, both of our engines (DIESELS) will still have a lot more life in them.

Relax and enjoy the Coach,

JMHO,

Mr.Mark wrote:
Holstein13, it was emphasized that we keep our engine at high idle if the engine is running and in 'Park'. We have a switch on the dash with a rabbit on it (high idle). I engage the switch after I start the engine after about a minute or so.

Interesting. Why do you wait a minute before putting it in high idle? I hit the high idle immediately upon startup. I noticed that the engine ramps up to high idle speed when I do this. It doesn't jump up to 1,000 RPM.

If I waited a minute to press my button, it would be time to put the coach in drive and leave. How long do you let it idle? Mine gets to full air pressure in less than a minute.

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.

Holstein13, it was emphasized that we keep our engine at high idle if the engine is running and in 'Park'. We have a switch on the dash with a rabbit on it (high idle). I engage the switch after I start the engine after about a minute or so.

The purpose is so that the engine is sufficiently lubed including the turbo.

Our previous coach had the high idle switch on the smart wheel. Our smart wheel has the cruise on the left and the engine retarder on/off, high/low switch on the right side.

MM.

Well, I don't know about these newer engines, but back when I was a trucker we had throttle cable controls for the idle. It was not good to let a diesel idle for long periods of time. I would sent the idle at about 1000 rpm's, this would get the oil pressure up and this was better for the engine. Today you want to ask someone that works on these newer engines.