To idle or shut-off: Which is best?

[rdsaustintx]

Here's a government report on offroad engine life:

engine life

On average, around 5 years for a small commercial diesel tractor.

It's interesting some parts of the report categorize use as residential vs commercial. In comparing the the two, the chronological lifetimes are similar even though the "residential" lifetime hours are pitiful. This suggests two things:

1. Something happens to equipment just because it gets old. (Stuff like rubber parts going bad.)

2. There is no (chronological) life extension from disuse. Might as well drive it /forums/images/graemlins/smile.gif

You can find a lot of hits on work to improve HST reliability, notably through black-boxing various control functions. I don't think our little machines have much of that.

Seal failure can eat hydraulic pumps and motors, either by allowing cavitation or causing hydraulic lock. JD has a neato seal failure algorithm on their big earth-movers. Using two seals at critical locations, they monitor oil pressure between the seals. If the pressure varies too much, one seal may have failed and it issues a diagnostic code.

I wouldn't fault any designer for a seal failing after 4-5 years. They are alternately sitting frozen, then frying in oil. Under full load (rare) these HST's are dissipating 4-5 hp as heat.

Happy trails

Russell in Texas

 

[HGM]

To be honest, I havent ready every post here. We've discussed this on several occasions so I have a good idea where most stand, as well as they of me.

RayH, has the prefered practice in my opinion. You should never let a diesel idle(base idle). This can be one of the worst things you can do to your diesel engine because the air cooling effect of the intake cycle will overcome the heat created by combusion. This causes more sooting and incomplete combustion as well as oil contamination. Generators, semi's, etc. rarely if ever are run at low base idle. They are typically set at 12-1800rpm to maintain operating temp and avoid these issues. Keep your air, oil, and fuel clean and run the engine as designed, it will likely outlive you. /forums/images/graemlins/blush.gif

Just couldnt resist adding my $.02, hope it helps /forums/images/graemlins/grin.gif

 

[Ed_L295DT]

The term 'wet stacking' may have originated from the old Cat (and other) engines that were subject to extended periods of idling; hard to start pony engines, pre-combustion chamber design, cooler idling temperatures, piston ring contraction, glazing of cylinder walls etc. Current use of the term wet stacking refers to the over-fueling that occurs at temperatures too low to allow efficient combustion. As near as I can tell, modern Kubota engines have the more efficient direct injection style, thereby more closely maintaining efficient fuel combustion temperatures in the combustion chamber than engines of past years.

Engines are designed to operate efficiently under load. Your engine operates at thermostat temperature when working and at a cooler temperature (less-efficient combustion) when idling. Water, a by-product of combustion, passes the cooler, contracted piston and rings into the crankcase where it mixes with the oil and creates a residue on the underside of valve covers, etc. Extended idling over the short term may have little effect on the engine. Long term results could show as uneven cylinder wall and piston ring wear (glazing) and/or premature bearing wear (contaminated lubricating oil). Periodic engine oil sampling has shown higher concentrations of fuel and water in extended-idling-period engines.

Forty years as a Cat mechanic have taught me to limit my idling periods to a maximum of five minutes at a point just above low idle.

 

[California]

<font color="blue">Forty years as a Cat mechanic have taught me to limit my idling periods to a maximum of five minutes at a point just above low idle. -Ed_L295DT</font>


Ok. That settles the question for me.


I'm surprised in 2500 views and 40 replies no one has mentioned shutting down as a good safety practice.

 

[SkyPup]

Kubota engines are NOT primarily DI engines, they are primarily IDI, only a couple of their larger over 50hp engines are DI.

One of the main limiting reasons is cubic inch displacement, number of cylinders, and the resulting cylinder size.

Direct injection does not work well much below 500cc combustion chamber size as the raw fuel from the multihole injectors ends up being on the piston crown and cylinder walls.

 

[rdsaustintx]

Just to agree with skypup (IDI): kubota mini diesels

If you check index there is also a sexy article about 50hp+ engines with 4 valves and center DI. Sort of a diesel hemi. vrooooom /forums/images/graemlins/shocked.gif