Idle Speed...why so fast??

[wowwee]

Hey There, I've got a 2008 model B2320. Once it's warmed up the lowest it will idle is about 1100 RPM. Anyone know if I will do any harm adjusting the speed a little lower? Maybe Kubota has to set it there from the factory just to meet emmisions standards?

Thanks, Dale

 

[yooper jim]

Set the idle lower and it will shake it's self to death. At least that is what I've heard. BX 2660 idles at 1250.

 

[timswi]

Set the idle lower and it will shake it's self to death. At least that is what I've heard. BX 2660 idles at 1250.

Yup, that's true...You want a smooth idle or it will shake itself to pieces.

 

[RadarTech]

I am constantly amazed at things like this..

1100 RPM to be smooth...


wow....

J

 

[rswyan]

Anyone know if I will do any harm adjusting the speed a little lower?

Hmmm .... well, it certainly may be true that a very rough idling engine "might shake itself to death" ..... but if I had to guess ....

It probably has more to do with the inherent nature of diesel engines ...

Diesel engines - at least the ones that I'm familiar with - tend to be somewhat cold-blooded creatures (possibly because they are so efficient) ..... and they really like to be worked to remain all nice and toasty at proper operating temps .....

Since a diesel engine runs as a consequence of the heat generated from compression of air igniting the fuel, one could theorize that below a certain speed a diesel might not generate enough heat to fully combust-ulate the fuel being injected into the cylinders .....

If the fuel is not being completely combust-ulated, then the un-combust-ulated fuel would likely go somewheres ....

..... and diesel fuel, being a solvent-sorta liquid (kinda) might tend to wash down the cylinder walls (gravity being what it is and all) - removing good stuff like, oh, say .... engine oil, which is intended to lubricate things - and then just keep right on going .... down into the crankcase ..... which might possibly result in fuel/oil contamination:

Crankcase dilution

.... and other similarly nasty stuff - like wet-stacking (otherwise known as mung and drool ):

Wet stacking

I can tell you for a fact, that the above is exactly why my dealer, when he set up our B2910, set the idle to 1200 rpm .... (I know - because I asked .... )

It's also the reason that the little 2.7 liter, 5 cylinder Mercedes diesel engine in my Dodge (Mercedes) Sprinter has an Espar D5 Hydronic coolant heater installed from the factory - this is a little heater that burns diesel fuel (kinda like a mini-torpedo heater, only it heats engine coolant) in order to keep the engine coolant at operating temps in cold weather, when the vehicle is idling alot (Sprinter's factory idle is around 700 rpm, is controlled electronically via the ECM, and cannot be adjusted manually - other than by the use of an "idle stick"), or being driven stop-n-go .... and won't stay at normal operating temps .....

Me personally ? .... given the possible alternatives, I'd learn to love the sound of that little orange oil burner, sitting there purring at 1100 or 1200 rpm ......

 

[RickB]

There's a two word answer:

Emissions standards.

 

[Egon]

In colder areas many diesel P/U's that do a lot of idling have a fast idle controller installed so the engine will stay warm.

Chances are the engine needs to be at a certain running temperature before a complete combust-ulate:thumbsup: can be acheived!

At -20C I've gotten quite cold while waiting in a line up in my truck.

 

[kuboman]

I have adjusted down every tractor I owned including all my kubotas. No they will not shake themselves to death. They all have a "sweet spot". My 2620 idled real nice at 800 rpm. Play with it and find you tractors spot. A slower idle will not hurt anything.

 

[timswi]

I have adjusted down every tractor I owned including all my kubotas. No they will not shake themselves to death. They all have a "sweet spot". My 2620 idled real nice at 800 rpm. Play with it and find you tractors spot. A slower idle will not hurt anything.

True, as long as you find a smooth spot...That violent shake is too much to take, at least for me. I don't like seeing the air filter etc shaking all over the place.

My BX will shake it self to pieces at base idle..The RTV1100 has a higher base idle so it appears. The 1100 has no shake at all, and it has the same basic drive train.

 

[AceDeuce]

My BX shakes so bad at idle it broke [from fatigue] one of the 1/4" steel brackets that supports the counterweight over the valve cover---I was amazed. Now I don't ever bring it all the way down. Instead I keep the RPMs up enough to make it run smooth. My uncle's 25 yr old 3 cyl. L2250 idles VERY low (only a few hundred rpm) and runs smooth as a baby's but. Go figure.

 

[RadarTech]

My BX shakes so bad at idle it broke [from fatigue] one of the 1/4" steel brackets that supports the counterweight over the valve cover---I was amazed. Now I don't ever bring it all the way down. Instead I keep the RPMs up enough to make it run smooth. My uncle's 25 yr old 3 cyl. L2250 idles VERY low (only a few hundred rpm) and runs smooth as a baby's but. Go figure.

I think it is all about the counter balanacing of the crankshaft....
slower the rougher-- makes sense to me...


J

 

[leonz]

Every properly installed three cylinder prime mover I have ever

been around or worked with behaves like this as it was was due

to the engines being bolted to the frame of the vehicle which

had a gas engine and had to be modified to accept this

Duetz Diesel with no rubber isolation mounts),

NO I was not responsible for that mess.



The 3 cylinder Duetz engines in our Ingersoll Rand Air Compressors

did not have these issues because they had the required rubber puck

isolation mounts.


Some machine builders simply bolt the engine to the machines,

which is what I suspect the problem is here due to the description

of the engines behavior at low idle speed. It is much less noticable

at the higher idle due to the engine speed increase.



The Duetz engines use a rubber puck with a drilled hole and steel spacer

to secure the engine mounting feet to the machines engine compartment

allowing the rubber puck to compress only as far as the steel spacer

pressed into the rubber puck used for the shock absorber.


The 3 cylinder Kubota engine is used in a lot of applications.


The Compact Utility Tractor market was simply another avenue

to sell engines and transmissions, which are shipped from

the Kubota home plant world wide, as they sell these engines

for water pumps, generators, miniature rice combines,

rice planters, stationary threshers, small construction machinery

including rollers, tampers, portable screens for gravel and sand

among other uses.


What you are describing completely is an issue of having no

engine isolation from the frame of the tractor.


(They either have a thin piece of conveyor belt between the

mounting foot of the engine and the frame

which simply aids the transmission of engine vibration

or simply nothing at all separating the engine from the tractor frame).

I will post what the engine isolation mount should be/look like

for the 3 cylinder engines when I find it shortly.


My former employers used conveyor belt because they did not want

to buy the pucks for the mounts as they felt they were not required.


All the Saulsbury fire pumps I installed were done this way and they continue

to do it that way.


leon

 

[warcloud]

my Bx 2360 sweet spot is 1600 rpm base idle is 1400 . idle at 1400 is shake raddle and role.

 

[RadarTech]

my Bx 2360 sweet spot is 1600 rpm base idle is 1400 . idle at 1400 is shake raddle and role.

did you get the blue suede smoke kit too???:laughing:

Justin..

 

[TheFlatlander]

Leon-These tractors have their engines on rubber mounts. That is why there are posts on here about the fans hitting the shrouds when plowing snow.

 

[leonz]

Leon-These tractors have their engines on rubber mounts. That is why there are posts on here about the fans hitting the shrouds when plowing snow.

Boy if they are rubber mounts are that small I would like to see what the mounts look like for sure-its almost as if the there is no steel spacer because these runt engines are mounted in other appliances with no issues.

The low idle should be balanced period just like the high idle; I am curious about the things I mentioned before and I wonder if the injection nozzles are part of the issue with fuel delvery and lack there of?

It worries me only because of aging engine parts and the dreaded piston slap which is of course not a bad as the dreaded dope slap from the Magliatzi brothers from Car Talk.



It again honestly leads me to the unbalanced crank issue/power train, flywheel, torque converter, once again.

Further detective work is indicated with a scope in the crank case to determine if weights are welded to the crankshafts of these engines for balance.

These engines are shipped from Kubota Corporation in Japan to all points on the globe for a lot of other machines and theres a termite in the office paneling someplace.

It would be worth asking neil if he has a crankshaft in his stock parts that they could run through with a dial indicator and metal lathe.


leonz

 

[leonz]

I think it is all about the counter balanacing of the crankshaft....
slower the rougher-- makes sense to me...


J

OK you lost me aceduece sorry-what counter weight?

the only exposed weight you should have is the flywheel pulley which carries the alternator belt and water pump if it is not gear driven.

If the crank pulley is not balanced thats another issue also and would be enough to shake at low idle with or without adequate motor mounts.(which is a no no).

 

[RadarTech]

OK you lost me aceduece sorry-what counter weight?

the only exposed weight you should have is the flywheel pulley which carries the alternator belt and water pump if it is not gear driven.

If the crank pulley is not balanced thats another issue also and would be enough to shake at low idle with or without adequate motor mounts.(which is a no no).

I was thinking about the counter weight on the crankshaft itself the large weights that help the centriful force so when the piston goes up this weights "help" balance out the force of the rotation..

Now, I spent most of my engine work time on small engines and small cars engines... I have NEVER broken down a diesal.. BUT I see no reason why a crankshaft would be that different...


Jed

 

[leonz]

Both the crank shaft and the flywheel must be balanced with weights if the casting is not machined into balance as the bearing will fail much sooner than normal.

this is no different than balancing tires but operating at a high RPM.:thumbsup:

 

[RadarTech]

Both the crank shaft and the flywheel must be balanced with weights if the casting is not machined into balance as the bearing will fail much sooner than normal.

this is no different than balancing tires but operating at a high RPM.:thumbsup:

maybe I was just thinking of a bad experience..

we had an old sears garden tractor.. dad said sometimes it just "lugged" due to the way the crankshaft was..


Jason