To idle or not to idle

[Anonymous Poster]

For those of us interested in maintaining our tractor in good condition I read a good article in the current issue of Progressive Farmer. Caterpillar states it is not good to idle your diesel for periods over 10 or 15 minutes. Reasons cited include engine temp going below 160 which leads to incomplete fuel burn, carbon build up on pistons,and injectors as well as condensate causing oil related problems.
Anyway you get the picture. The article can be accessed on the NET at the progressive farmer website.
Happy Tractoring
Greg H

 

[gerard]

Strange, my problem with extended idling is the engine temp creeping up (at lease with ambient temps above 60deg f) due to the coolant being ciruclated more slowly. I generally bump the idle up a little if I'm going to idle for awhile. I know diesels generally idles for long periods and are designed for that (trucks sometimes idle for 8 hours at a time) but I usually shut mine off and restart since it starts so easy, especially after warm. Anyone out there notice a temp drop when idling?

 

[Bird]

Gerard, on the tractor's temperature gauge, I've never noticed any change, but that's may be because I've never let it idle long enough. But it is a fact that generally you worry about a gasoline engine getting too hot and a diesel getting too cool when left idling for long periods of time, in addition to the other potential problems mentioned. A lot of big trucks are left idling for extended periods, although some may be set at a faster idle. My brother uses a GMC Top Kick with a 200hp Caterpillar engine and it's run 10 to 12 hours a day, much of that time "idling" and never shut off from the time it's started in the morning until he shuts down at night, because he has to keep the lights, inverter, heating and air-conditioning working in the back as well as in the cab. It has a control knob to set it up at a fast idle when it's parked. He said if he doesn't use that feature, it'll never overheat in the summer (100+ temperatures), but it'll get too cool in the winter for the heater to work properly.

Bird

 

[patton]

A guy with John Deere Engine Engineering told me their standard recomendation is to never idle below 1000 rpm (we were discussing small diesel engines 30-50 hp) but above that is ok, and desirable in many cases.

I guess the answer depends on your definition of idle.

Pat

 

[TomG]

I've seen the gauge on my Ford 1710 gauge go down at idle. Yesterday I drove 10 miles on a highway. The meter stayed at what I know is the thermostat regulated temperature. I idled at 800 rpm for about 5 minutes to cool down and then noticed the gauge was below the normal operating temperature. Cooling down diesels is good practice I hear.

On the highway I ran around 2600 rpm. After a late summer of mostly chugging around doing loader and pallet fork work, the engine had started puffing smoke on acceleration. It didn't do that after the highway run. It's also good to run diesels fairly hard from time to time I hear.

I believe that the difference in idling between diesel and gas engines is that gas engines have throttle valves. Due to the valve, gas engines have high intake manifold vacuums when the valve is closed at idle. Diesels don't have throttle valves and always have relatively low vacuum. With the high vacuum, gas engines are burning relatively rarified air at idle. In effect, there's less air to warm. In comparison, it's sort of like a cold wind blowing through a diesel. Heat from the low fuel delivery at idle may be insufficient to keep the engine at operating temperature.

 

[Anonymous Poster]

Bird you hit the nail on the head. The article specifically advised against slow idle. Cummins also advised that high idle is the way to go if you must idle over 10 or 15 minutes.
From what little I know about diesels the reason for problems at low idle is that unlike a gas engine that always runs at a 14.7 air/fuel mixture, the diesel is absolutely miserly at idle and onley needs minute amounts of diesel. It doenst need enought to maintain engine temperature above 160 top 170 degrees.
Just my 2 cents
Greg H

 

[roysallis]

If I remember correctly the JD manual says to idle about 1100 - 1400 rpm.

 

[thebonepile]

Re: cooling down

A farm kid here - we have a bigger (120hp) IH diesel farm tractor - we got it used and it had a pyrometer (measuring the exhaust temp) when we got it. If we take it out and work hard (pulling 21' disk, plowing) the exhaust temp will go up and stabilize about 1000 degrees, If you were to get to the end of the field and shut this tractor off, it is very hard on some items (especially the turbocharger) to let it cool from 1000 with no fresh air or oil circulating.....

Basically the drive from a field back home, is long enough for the tractor to cool back down - getting temp back down to 600 degrees or so

Little jobs like idling, mowing, grinding feed, etc - none of these work the tractor hard enough to raise the guage much above the 600 degree mark (which is basically the lowest indication)

 

[Thomas]

Re: cooling down

Have you flush both cooling system real good.
What gear do you run your tractor in while pulling 21' disk..maybe a low gear and tad more rpm would help.

How often does the turbo kick in if pulling up slopes.

The good side when she cooling your also getting break. /w3tcompact/icons/wink.gif

Thomas..NH /w3tcompact/icons/wink.gif

 

[radman]

Re: cooling down

Thomas: Since "thebonepile" has not yet responded to your questions, maybe I can help some. I also do some farming with our largest tractor around 190hp. His comments concerning turbocharged engines on farm tractors are correct. When a turbocharged tractor is pulling a decent load, the exhaust temperature will increase significantly. When pulling, the tractor's turbo is working all the time. The turbo is more efficient at higher rpm. When the tractor is working, the engine runs near wide open and at least pto speed. Hp and efficiency are at higher rpm and turbo speeds. Generally, the size of implement should be matched to the size of tractor. ie, larger tractor = larger disc. Large tractor and small implement is inefficient. Ag trators are most efficient with about 8-10% wheel slippage. Too much weight/traction and no slippage is inefficient. Too much slippage means excessive tire wear and inefficient. Our tractor will actually tell how much wheel slippage is present based on determining actual ground speed (tractor has radar) and comparing that to wheel speed. Why would a tractor need radar you might ask? If the true ground speed is known, the proper amount of seed, chemicals and fertilizer can be applied even allowing for wheel slippage. Some ag tractors also have GPS systems installed. Why GPS? If soil samples are taken of the land to be planted and the location of the samples are known, the results can be put into the GPS systems to adjust planting, chemical and fertilizer rates to different soil conditions in the same field to obtain maximum yeilds and at the same time to reduce seed, chemical and fertilizer cost. Sorry, I got off track with my post but some of things newer tractors can do are really quite phenomenal.