Idle Speed for Tractor Warmup ?

[frank_f15]

I START MINE ABOUT 1000 or 1200 Rpm, and let it warm up in cold weather at least 10 min. i usually set the start up idle , before i shut down. this may sound silly but i like to go by the sound of the engine, to determine what is best for any particular tractor.

 

[KubotaBling]

Yah after 10 minutes your basicaly got the combustion chamber colder than 300 degrees and it starts puking white smok diluting the oil and scoring the walls of cylinders. I've heard "extended" idle to be anything over 10 minutes it usualy takes that long for egt to drop to below 300.

I'd wait enough to get the oil around and pistons and stuff to work a little i'd say 10 mintues a little too long so probaly 5 minutes mines in a heated garage so i've not done too much cold starts other than myself i allow about 10 minutes to deciede if it's worth going outside usualy not and come back in and watch tv eliminates cold starts /forums/images/graemlins/grin.gif

 

[5030]

CowboyDoc:

You mean "Pyrometer"

 

[art]

You are good with 1300 to 1500 tops is good. Ten minutes is fine.

 

[5030]

</font><font color="blue" class="small">( Yah after 10 minutes your basicaly got the combustion chamber colder than 300 degrees and it starts puking white smok diluting the oil and scoring the walls of cylinders. I've heard "extended" idle to be anything over 10 minutes it usualy takes that long for egt to drop to below 300)</font>

That is not quite right.....

The temperature in the "combustion chamber itself" never drops to 300 degrees. The temperature of the surrounding metal mass drops as the inherent heat of compression and combustion is not enough to maintain the heat in that mass. As far as dilution of the lube oil and scoring of the cylinder walls, well, that's pretty rare and will only happen with an engine that has numerous hours on it and is probably in need of a rebuild. Idling a diesel engine for long periods is more wasteful of fuel than anything else.

New technology engines, those with electronically controlled injection timing will compensate themselves for the extended idling by advancing the injection timing to promote a cleaner burn. The white smoke (unburned diesel) is due to the fact that as you suddenly advance the throttle on a cold (mass) engine, you get incomplete combustion and the unburned (though heated) fuel goes out the exhaust pipe.

Diesels as a rule don't "carbon up". You will get a carbon ring in the liner at the top of the piston stroke, a light coat on the piston crown and combustion chamber, but that's about all. The heat developed in the combustion chamber during working periods, burns off any carbon buildup.

A pyrometer (exhaust temperature) gage monitors the exhaust temperature to give you an idea of relative efficiency. It's more of a tool in watching the internal temperature of the engine. An egt of more than 1100 degrees for an extended period of time signals that you are destroying the pistons or valves. Without going into a long dissertation about internal combustion temperature limits, it is suffice to say that a pyrometer thermocouple placed on the "cold" side of the turbocharger should never register more than 1100 degrees Fahrenheit for more than a few seconds. The actual temperature in the combustion chamber is much higher, usually more that 300 degrees higher. The benchmark threshold for internal destruction is 1500 degrees Fahrenheit.

 

[cowboydoc]

Kind of Daryl. The turbo temp controller is hooked into the turbo temperature via a pyrometer. When the turbo temp drops below 300 then the engine will shut off.

 

[DieselD]

5030, Your close but still off a bit.
EGTs can fall to temps less than 300 in a diesel, so low that you can washdown the cylinders.
Too low of an idle can oval bores and hurt piston skirts.
You really don't want to see temps of 1100 degrees post turbo.
Also it depends on the turbo/type of manifold/1,2 port turbo on how you can read pyro temps post turbo. Its risky.
Preturbo is the only ture way of telling.
Post turbo is for telling when to shut , for keeping the oil from coking on the shaft.
Diesels also love constant rpms usually 1400~2600 RPMS
A raised IDLE means raised oiol pressure.
Danny

 

[KubotaBling]

that's true i was refering to the egt not the temp of combustion chamber but i find idling a engine in cold weather actualy draws heat from the combustion chamber. I have several engines i use daily and started cold i found that initaly the egt would be 300+ then drop the longer i idled.

It is recommended to change rpm after 10 minutes regardless to prevent combustion chamber from cooling this is out of the cat owners manual for 3208 + 3126E.

I have seen diesels score piston walls and damage engines from idling when the engines cool down the rings and pistons don't fit the space between the fuel tends to puddle on the extreme edges of the combustion chamber where the heat is drawn from chamber the unburnt fuel goes by rings and tends to cause rings to stick etc.. this is from seeing a couple of engines and reading some tech pages from maintance pages and technical recommendations for fleet operations.

Your results may very.. I ended up getting a heated garage no problems with any of that now.

 

[Barnee]

My Kubota manual says to set the throttle lever to half-way before starting the engine. Once it starts I make sure it stays 1200-1500 rpm. It then says to allow for 5 min. warmup for the engine and 10 min warmup for the trans fluid (>32 deg) for what it's worth.

 

[Bird]

</font><font color="blue" class="small">( My Kubota manual says to set the throttle lever to half-way before starting the engine )</font>

My manual said the same thing, and of course I would assume whoever wrote Kubota's manuals knows more than I, but I just never wanted to have one revved up that much immediately upon starting, so I always started mine with the throttle all the way to idle, then when it started, I slowly increased the throttle setting to the 1200-1500 to warm up.