Confused about tractor RPMs + L, M, H (Kubota L3301)

[minthral]

Hi all,

I recently got my first tractor and am confused about the RPM throttle. I am used to using riding mowers...mostly john deere garden tractors and some zero turn. I always just ran them at full throttle (WOT).

The tractor has an indicator for PTO engine RPM (slightly below WOT). When I first got it, I did some loader dirt work and backhoe digging (learning curve for sure). The manual says it is recommended to run the B77 backhoe at 2700 (rated RPM) or 75% of that if you prefer to have slower speed and make less noise. I think the 75% is the PTO mark and that's where I ran it...I would say it moved 'fast speed' at PTO RPM and was actually considering lower RPMs for slower speed.

I tried to move the tractor around with the loader and backhoe (+ filled rear wheels). In WOT H gear, it really struggled up grade even at WOT, so I don't see the point of H atm. In M gear, the hydro really whined a lot as it struggled up grade in lower RPMs, but does fine in higher RPMs. In L gear and WOT, it moves a bit slow (hydro pedal to floor), but no struggling...lower throttle was too slow. So this leave me the following options:

H WOT - flat ground/ road going fast
M almost WOT (around PTO mark) - mowing/ PTO work
L WOT - loader/dirt work

Notice the trend here is basically use high RPM. Here is where I'm confused: Why does the tractor even give you the option of using lower RPMs? So far it seems that you basically have to run it near WOT, though I admit it's louder than I was expecting. This doesn't bother me since I always use noise canceling earbuds when working.

What comes to mind is fuel saving? I ran the tractor around PTO mark for about 2 hours and the fuel gauge is still basically on top, so if the tractor is that efficient, I don't really care about saving fuel.

Also it's possible to go higher than PTO RPM speed while using PTO by about 25%. What happens when you do this? Your PTO spins faster and you got more power? Seems like that would be desirable?

I also notice the hydro REALLY whines and moans at lower RPMs. It screams at higher RPMs, but is more blended with the engine noise. Per the dealer, they say you should not run it at low RPM a lot because it will force regen cycle sooner or clog up the exhaust.

At this point I'm convinced I should just always run it at 75-100% throttle and trying to see if I'm missing something.

 

[TheOldHokie]

Hi all,

I recently got my first tractor and am confused about the RPM throttle. I am used to using riding mowers...mostly john deere garden tractors and some zero turn. I always just ran them at full throttle (WOT).

The tractor has an indicator for PTO engine RPM (slightly below WOT). When I first got it, I did some loader dirt work and backhoe digging (learning curve for sure). The manual says it is recommended to run the B77 backhoe at 2700 (rated RPM) or 75% of that if you prefer to have slower speed and make less noise. I think the 75% is the PTO mark and that's where I ran it...I would say it moved 'fast speed' at PTO RPM and was actually considering lower RPMs for slower speed.

I tried to move the tractor around with the loader and backhoe (+ filled rear wheels). In WOT H gear, it really struggled up grade even at WOT, so I don't see the point of H atm. In M gear, the hydro really whined a lot as it struggled up grade in lower RPMs, but does fine in higher RPMs. In L gear and WOT, it moves a bit slow (hydro pedal to floor), but no struggling...lower throttle was too slow. So this leave me the following options:

H WOT - flat ground/ road going fast
M almost WOT (around PTO mark) - mowing/ PTO work
L WOT - loader/dirt work

Notice the trend here is basically use high RPM. Here is where I'm confused: Why does the tractor even give you the option of using lower RPMs? So far it seems that you basically have to run it near WOT, though I admit it's louder than I was expecting. This doesn't bother me since I always use noise canceling earbuds when working.

What comes to mind is fuel saving? I ran the tractor around PTO mark for about 2 hours and the fuel gauge is still basically on top, so if the tractor is that efficient, I don't really care about saving fuel.

Also it's possible to go higher than PTO RPM speed while using PTO by about 25%. What happens when you do this? Your PTO spins faster and you got more power? Seems like that would be desirable?

I also notice the hydro REALLY whines and moans at lower RPMs. It screams at higher RPMs, but is more blended with the engine noise. Per the dealer, they say you should not run it at low RPM a lot because it will force regen cycle sooner or clog up the exhaust.

At this point I'm convinced I should just always run it at 75-100% throttle and trying to see if I'm missing something.

I have the L3901 and no backhoe.

H range is a road gear and good for little else.

M range for general work like mowing. Engine runs at 540 PTO speed. That is what your implement is designed for and over revving is not good for it.

L range for more power but slower ground speed on hills. Engine RPM same as M.

If its not working I shut it down rather than having it sit at idle.

The "set it and forget it" HST transmission is designed to use infinitely variable gearing not engine RPM to control ground speed.

Dan

 

[minthral]

I have the L3901 and no backhoe.

H range is a road gear and good for little else.

M range for general work like mowing. Engine runs at 540 PTO speed. That is what your implement is designed for and over revving is not good for it.

L range for more power but slower ground speed on hills. Engine RPM same as M.

If its not working I shut it down rather than having it sit at idle.

The "set it and forget it" HST transmission is designed to use infinitely variable gearing not engine RPM to control ground speed.

Dan

Right, so you don't run lower than PTO RPM either?

 

[TheOldHokie]

Right, so you don't run lower than PTO RPM either?

For non-PTO work (e.g. loader/grapple) maybe a little lower but not much - 1500+

Dan

 

[Bmyers]

I run mine (L3560) lower than PTO speed, depending on what I'm doing. Typical 1500-2000RPM, just depending on what I'm doing. The lower RPM you run, the quicker you will need to regen. If you are running at higher RPMs the longer in between regens.

 

[NCL4701]

The power v speed of the HST is kind of counterintuitive in that if you need more torque you need LESS pedal. So if it’s struggling a little up a hill in H, giving it less pedal may give you the torque you need to get up the hill.

However, you pretty much figured out the ranges. H is “road gear”: good for traveling between work areas but not worth much for work. M is a balance between speed and torque: good for mowing and a bunch of other work activities. L is good for digging or pushing into a pile with the loader or anything else where you either need to move slow or get max torque.

Running a PTO implement such as a mower, they have a speed they’re designed to run and deviating from that faster or slower may or may not be important. A mower isn’t going to be extremely sensitive but if 540 PTO rpm is where it’s designed to run, I wouldn’t just assume faster is better. That’s actually why dedicated lawnmowers are always run WOT. They’re governed to be at the designed mower deck RPM at WOT. Your tractor is more flexible than that as it will do more than mow.

Aside from that, run it where it’s working well for what you’re doing. Hydraulic pressure (power) is constant because the pump is a fixed displacement pump. Hydraulic flow (speed) varies with RPM. If you want more speed, increase RPM. Less sensitive controls for delicate work, reduce RPM. Hydraulic power remains the same.

Same experience here with fuel efficiency on the Tier 4 common rail engine. Unlike the mechanical diesels doesn’t seem to be much tied to RPM. Definitely tied to load. WOT for mine is about 2800 RPM. 540 PTO is about 2700 RPM. I normally run it around 1800 to 2200 unless pulling hard or running something on the PTO. Regens have been 50 to 70 hours apart so far except for the first one, which was about 20 hours.

Have heard hydro whine on the L’s is pretty loud. Not bad on mine so maybe just the smaller L’s? Anyway, if it’s really screaming much louder than normal I’ve always taken that as it screaming for me to downshift the range or back off the pedal or both. Doesn’t take long to figure out what “normal” is.

BTW, before getting the Kubota I had several thousand hours on 1940’s and 50’s era gassers with clutch/stick gear trans, redline at 750 RPM for one and about 1000 RPM for the other. The higher RPM, HST, DPF, hydraulic hoses and valves all over everywhere; it was (and is) a learning curve, but worth a little study and practice.

 

[85Hokie]

Your old mower was a gas engine - designed to cut the "best" at a rated RPM - thus that little notch the throttle fell in was the perfect spot.......

A diesel is a different animal - it typically makes more low end torque than any gasser can and can run longer on the same amount of fuel.

With that being said - running a diesel at a "low" RPM for fuel saving is a myth - most diesels have a sweet spot - that is typically 50% up the rpm range, running lower can burn more fuel and running WOT will burn more fuel - chart below is not your engine, but rather a typical diesel tractor engine.

Now with the tier IV engines - running a low RPM is rather stupid - allowing the tractor to idle for a long time will actually create problems!!! Not to say you have to run it balls-to-the-walls all the time, but these new tier IV's need to run hotter so you do not have to regen when you least expect it.

As for ranges ........... as Dan mentioned - High is typically used on flat ground, simply to get from point A to point B as quick as possible, real work will not be done - especially with that 800+ monkey on your back (HOE)

My BX has two ranges - and in H range, forget going up any incline, my machine cannot go up any incline more than about 10 degrees - and that is whining it's ass off!!!

Never trust you fuel gauge - that is about as accurate as trusting a politician's verbiage!

AS for going beyond the 540 RPM's specs - not a lot is gained by making the PTO spin a little bit faster, remember, those devices where DESIGNED to work at the 540 RPM - anything faster is NOT better, rather it can be detrimental if something goes south! They place those number on the gauge for a reason - those engineers do know some thing WE do not.........

As for the whine - once you change your HST oil..... it will be better, using lower gearing will make it better too.

as for you last statement:

"At this point I'm convinced I should just always run it at 75-100% throttle and trying to see if I'm missing something."

spot on!!!!


the only exception MAY be when using the HOE...... sometimes 50% throttle is helpful, but once you get good at using the hoe, you will find that you want to move quicker thus the RPMS need to get up there near WOT.

 

[jyoutz]

L = loader
M = mowing
H = highway

 

[Freeheeler]

My experience is completely different. I can run in high with much less that wot and still not bog down. In mid range I can move around at idle and usually don't go over 2000 rpm for traveling around the yard. I've been very pleased with the L, M, and H ranges. I also have the BH77 and rear tires filled. I'm assuming the biggest difference is that although my big B has essentially the same loader and backhoe capabilities as the L's, it weighs substantially less. The L's extra weight makes it much better at ground engagement work, but it takes a lot more hydro power to move that weight around, especially up hills. This was a big part of why I went with the B2650vs the L2501 or L3301 since I don't do much ground engagement work. For the same HP tractor, the heavier one is going to need to use either a lower running gear or more rpm or both to move at the same speed as the lighter tractor. I think that the more you use it, you'll learn to appreciate having all 3 ranges to choose from.

 

[Henro]

Does the L3301 have the tier 4 emission system components?

If so, you may have to adjust your operating practice to prevent damage to the system, from what I have read here.

Seems running the engine too slow clogs up the diesel particulate filter, if that is what it is called. Or prevents proper regen... BUT what do I know really, other than I don't want a tier 4 tractor...

My tractors are pre tier 4 emission hardware, so I have little knowledge of tier 4 operating requirements other than reading sad stories that have been posted sometimes.

 

[minthral]

Turns out someone was right. I think my fuel gauge must be broken. There's no way after 5 hrs of usage fuel should be full...I look into the tank and say it's only about half full.

 

[Bmyers]

Turns out someone was right. I think my fuel gauge must be broken. There's no way after 5 hrs of usage fuel should be full...I look into the tank and say it's only about half full.

I can run for several hours on full, but when the gauge starts to move, it is time to think about fueling up. It quickly retreats south once it starts moving.

 

[Freeheeler]

My fuel gauge is digital and seems to be accurate. Anyone know if they use a different pick up style for digital vs analog? I would think if it's inaccurate it would be the pickup, not the gauge. My dad's BX has an analog gauge and it shows full until about half empty then goes down quickly.

 

[minthral]

Called the dealer about the fuel gauge. They said it's normal and something they get plenty of calls on...apparently they almost overfill it and the gauge only starts to showing later. Basically it’s not accurate and once it starts dropping, it will drop more rapidly. Or so they say. Depending on slope, it’s bouncing from full to 3/4 after 7hrs on the tractor, so I think the actual gauge works and it’s more of a question why it’s inaccurate, so makes determining how much fuel was used difficult.

 

[minthral]

My fuel gauge is digital and seems to be accurate. Anyone know if they use a different pick up style for digital vs analog? I would think if it's inaccurate it would be the pickup, not the gauge. My dad's BX has an analog gauge and it shows full until about half empty then goes down quickly.

Not sure, but think it’s analog and similar situation as BX for the L.

 

[sheepfarmer]

Called the dealer about the fuel gauge. They said it's normal and something they get plenty of calls on...apparently they almost overfill it and the gauge only starts to showing later. Basically it’s not accurate and once it starts dropping, it will drop more rapidly. Or so they say. Depending on slope, it’s bouncing from full to 3/4 after 7hrs on the tractor, so I think the actual gauge works and it’s more of a question why it’s inaccurate, so makes determining how much fuel was used difficult.

Easiest way if yours doesn't display fuel used (check owners manual for panel settings, it is recorded by computer controlling fuel flow to common rail), is to fill it full, look at the hour meter and record. Then the next time you fill it up see how many gallons it takes to top off. The plastic diesel fuel cans have measuring marks on the side so you can see how much you are putting in. Another look at the hour meter, subtract, and you have gallons per hour.

 

[thirdroc17]

Sounds to me like your running up against the inadequacy of the hydro drive. Gear drive is far more efficient.

Most Americans are too lazy to push in a clutch, thus gear drive tractors, of all sizes from 10HP up, are available virtually everywhere but the United States.

 

[NCL4701]

Don’t know about Michigan. In this part of the US gear drive CUTs are still available.

Not sure you can find a clutch and stick / reverser lawnmower, or skidsteer, or wheel loader, or forklift, or dozer, or track loader, or a lot of other types of equipment but utility and compact utility tractors can still be had in gear drive. Unless you want one without a reverser. You’re probably correct that you can’t get a new utility or compact utility tractor that’s true clutch and stick only without a reverser of some sort. That’s the way our older tractors work: mechanical dry clutch, no reverser, nothing synchronous, reverse is just another gear in a very basic gear box. There are operational advantages to both gear and HST. Which is “better” depends on what you’re doing with it. Having run gear as described above many thousands of hours and HST a few hundred hours I’m not sure HST is less physically taxing, it’s just different.

There are certainly lazy people in the US. I suspect there may be lazy people in other countries as well. I don’t suspect lazy people anywhere are out working their land on a tractor regardless of transmission type.

 

[Bmyers]

Sounds to me like your running up against the inadequacy of the hydro drive. Gear drive is far more efficient.

Most Americans are too lazy to push in a clutch, thus gear drive tractors, of all sizes from 10HP up, are available virtually everywhere but the United States.

My guess for the gear drive being in other parts of the world verses US has nothing to do with laziness, but with cost. Gear drives are cheaper and been around longer. US, higher income level brings the newest equipment to this market in mass.

 

[GreensvilleJay]

re: My fuel gauge is digital and seems to be accurate. Anyone know if they use a different pick up style for digital vs analog?

Your tractor has an ANALOG sensor, same as 99.44% of all tanks in all vehicles. While your readout (gauge) may be digital, the 'computer' reads the sensor, does some math, then displays the result.
A TRUE 'digital' sensor(zero moving parts) would be very expensive to make,depending on the resolution needed although you can make one with a several reed switches and a floating magnet.