BX 1800 ENGINE LIFE EXPECTANCY

[ProScape]

one more note...im not suggesting you dog the engine ripping out perma frost after just starting it but i am suggesting letting the engine "warm-up" at idle is both bad for the engine and wasteful.

 

[vtsnowedin]

What about shutting off your turboed diesel when it is running at full operating temp without letting it idle long enough to cool the turbo bearings? My tier three engine needs some time to cool down before it is shut off.

 

[zd21]

I concur with everything in your post, rScotty. Within reason, lower RPM reduces wear per hour. Reasons are several but include more moderate metal temperatures, smaller imbalance forces, and less friction from which to shed heat. Several long-life generators use commercial diesel engines, but run at less that usual RPM to reduce noise and wear.

 

[zd21]

Running a modern engine, gas or diesel, less than full throttle in a tractor does in fact cause additional wear for several reasons. The "old" days of how your father's father or whatever ran a tractor are well past. Modern engines running on ULSD must be run at full throttle as designed for the application. Running at less than full throttle while even doing light work causes excess heat or not enough heat in an engine depending on the load. This in turn leads to carbon build-up and valve problems. This is especially true of tier 3 and 4 emission compliant engines. In fact, even a Cummins or International over the road diesel run on an in-town delivery truck will have problems unless taken out on the highway and "opened-up" to higher RPMS. Google the relatively new "International MaxxForce" diesels and read about the problems they are having with them in applications that do not see high RPM loads such as in-town delivery, airport shuttle and school bus applications.

The newest tier 4 and IIIB engines use EGR (exhaust gas recirculation) and many use DPF (diesel particulate filters) which require an engine run at a higher temperature then "older gen" diesels.

Basically the "crap" that diesels used to exhaust now gets puked back into the engine and "recirculated".



A modern Diesel engine has a narrow RPM band for proper and efficent operation. On most modern tractors in order to achieve the proper PTO speeds the engine is designed for full throttle operation. Anything less during a load runs the risk of lugging and creating excess heat and stress on the engine and / or too low of cylinder head temps resulting in excess carbon, emissions systems problems and ultimately valve train issues.

More importantly than the engines, which are almost bullet proof anyway, is the hydro pumps. they are designed for a specific RPM and tractors / ztr mowers etc are designed around the pumps. Even if doing light work the tractor itself doesn't get any lighter and has to be moved around regardless of what you might be doing with it...even just driving it down the drive way. The hum you hear with hydro pumps at low RPMs is lugging of the pumps and I promise you will see significantly reduced longevity on pumps run at less that full throttle.

Also, when running an engine and hydro pumps at less than full RPMs the following occurs:

--less oil pump volume circulating and less pressure for both lubrication and cooling (this applies to both engines and hydros....in an engine it might even under some circumstances cause a lack of lubrication / burned valves and failure)

--less engine coolant being circulated through the radiator (the water pump is RPM driven, same as oil pump)

--excessively high or low cylinder head temps causing multiple problems as stated above / carbon build up

--harmonic vibrations that can damage the tractor or even frame....diesel produce destructive harmonic vibrations that can even crack frames and welds. If running a unit at less than full throttle which is what it is designed for you may cause the vibrations to occur (you may or may not even feel them) and can damage your tractor

--damage to implements that require 540 PTO / I have seen so many people using rotary and finish mowers at less than the 540 spec / this causes increased wear to the gear boxes etc

Nothing good comes from excess idling and running a modern diesel at less than full RPMS as designed.

Older diesels are different just like older carburetor cars needed the throttle pumped to set the choke and modern fuel injection does not.

I know there will be anecdotal evidence to the contrary of what I have said....someone out there has run at less than full throttle for years and thousands of hours without problems etc or maybe the problems just have not shown up yet. It like having high cholesterol...you wont necessarily see the problems until later and with a diesel that could be into the thousand plus hr mark. I can show you an example of a 89yeor old pack to 2 pack a day smoker that is healthy.....there is always an exception!

I have an older BX that I keep at my shop and run a PTO generator with day in and day out at 540 PTO which means 3150ish engine RPMs. I have had 'Bota diesels hit the 10,000 hr mark and still run.

I stand by run it at full RPM and the work / rebuilds my shop saw over the years confirms this as well as every dealer training session I have been to on Kubota, Yanmar, Cat, Kohler, Briggs, Kawasaki etc.

I agree with the summary of Kubota engineering actions to meet Tier 3/4 emission standards. I don't agree with the rationale for running engines at peak RPM for maximum life. Modern engines with few exceptions are designed to perform well at a wide range of RPM. True, maximum fuel efficiency occurs over a relatively small RPM and load range, but this has always been true of the internal combustion engine. It has little to do with engine life. The harmonic vibrations you refer to are an engineering responsibility to identify and eliminate during machinery design. The engine RPM range in which this might occur on a specific engine installation package would depend on the specifics of the design. Where vibration is a critical issue, more engine cylinders, added balance shafts, rubber mounts, etc. can be applied.
The fact is, most modern engines last a very long time, regardless of wide variations in loading and engine speed.

Oh, yes, the engines that are designed for one RPM, or a very narrow range. These would include the giant ship diesels by Sulzer-Wartsilla and a few others. And they run in the 100 RPM area. Also include stationary power generation diesels which can be optimized for one RPM. Both these low RPM engine categories are known for exceptionally long engine life.

 

[94BULLITT]

Look at a lot of small engines on push mower, generators, pressure washer etc. The throttle is set wide open all the time on them because people are not smart enough to run them at the proper speed. Also air cooled engine will overheat if the RPMs are too low because the flywheel cools it. I know a guy that used to own a tractor dealership with his family. One of my customers had just bought a Mahindra and was talking to him about the break in procedure on it. The guy that used to own the IH dealer told him it should be ran at full throttle all the time.

 

[MHarryE]

I have seldom run my new tractor at full rpm because most work has been PTO work and 540 RPM on the PTO is at 2100 and high idle is 2300. My Kubota has a max speed dial you can set so you don't have to fool around tweaking it to get 540. Also the book recommends 2,000 for typical loader work. At regen it will boost the engine above low idle but not to high idle. Tillage work - yes, it will be at full throttle. As for warm up, my book says warm up for 5 minutes above 32, 10 to 20 minutes at 14 to 32, 20 to 30 at -4 to 14, and more than 30 below -4 whether or not it is equipped with a block heater. Kubota's concern is transmission (hydraulic) oil. This is for both my L5740 and M135GX.

Of course the book says to run at low engine speed for the first 50 hours. Yeah, right, I'm going to putter around for 50 hours when there is hay to chop and the chopper takes all the power I have. It would be like telling a combine owner (part of past engineering career was combines) to run at part throttle and pour grain on the ground. To prevent customers from running less than high idle we had a throttle switch - low idle or high idle, nothing in between. Next career vibratory compactors. Same thing, switch for either low or high idle. Design life 10,000 hours but expect a lot more.

 

[steveky]

Wow, this question turned into quite a long thread. I have my BX now, changed oil, hydraulic oil and all filters. Wasn't sure when the last service was performed as it had 550 hrs when it arrived, so I thought I would start with a clean slate. I really enjoy mowing with this little tractor, it is one smooth running little machine. I want to thank all of you for your posts and sharing your knowledge, I learn something everytime I sign on to this site.

 

[Turbys_1700]

one more note...im not suggesting you dog the engine ripping out perma frost after just starting it but i am suggesting letting the engine "warm-up" at idle is both bad for the engine and wasteful.

My 03 Ford F350 with the 7.3 Powerstroke has a high idle feature...
If you crank it up in the morning in the winter to let it warm up after a minute the high idle control program takes over and keeps the engine at an RPM designed to alleviate coking
The exhaust gives off a very loud hissing sound when the high idle is on...
As soon as you hit the accelerator the high idle goes off...
Good engineering...