Maybe an odd question but here goes

lmichael

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Kubota G2160
Apr 23, 2021
246
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Rockford IL area
I have now owned 3 tractors with hydro transmissions. Simplicity Sovereign, Honda 4514 and now this Kubota G2160. But one thing has always puzzled me about HST units. Is it better to run at your desired ground speed with as low an engine speed as possible or better to run the throttle up and "feather" the HST?
(Mower performance aside). Though I know mower performance is better with higher blade (engine speed) and lower ground speed. But what is best for the hydro? Asking for a friend LOL
 

GeoHorn

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M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
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Texas
The HST machinery I own warns against running at low engine speeds because that results in low fluid-flow which results in heat build-up. Travel-speed should be regulated with the pedal or speed lever rather than with engine.
As an example, my Ferguson Compactor-Roller has a hydraulic oil temp gauge and it runs much hotter at speeds below 50% Max RPM versus 75% or higher. Ideally, hydraulic fluids should be kept below 200-degrees to prevent oil deterioration...and below 180-degrees to prolong glands, seals, O-ring and hose lives.

Hope that helps.
 
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B737

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LX3310
Jun 9, 2019
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Thank you Geo for sharing that ^^ good to keep in mind

I also read somewhere, it's better to run with pedal full down as it will allow more flow, more cooling. Like using full pedal in low gear vs 50% pedal in mid gear.
 

lmichael

Active member

Equipment
Kubota G2160
Apr 23, 2021
246
94
28
Rockford IL area
Thank you Geo for sharing that ^^ good to keep in mind

I also read somewhere, it's better to run with pedal full down as it will allow more flow, more cooling. Like using full pedal in low gear vs 50% pedal in mid gear.
Which pedal? You mean the HST or are you referring to the throttle?
Maybe too, I may want to install an oil temp gauge in the HST? Beside, the darn thing is so fast (ground speed) I can't imagine running at much over idle at full hydro pedal LOL. I only have 1/2 acre not that far to travel :D
 

GeoHorn

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M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
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Of course, I don’t know about YOUR particular machine..but mine operates like this:

The hyd pump output is directly proportional to the engine speed because the pump is directly bolted to the flywheel. The amount of fluid directed to the hydraulic-drive-motor is regulated by the speed lever/pedal (because it controls the swash-plate and therefore the pump piston-travel)... and any excess flow not utilized by the drive-motor bypasses it and passes thru the oil cooler before dumping back into the reservoir.

If low engine speed is used then less “excess” fluid is sent thru the cooler because more fluid is required by the drive motor for similar speeds.
 
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B737

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LX3310
Jun 9, 2019
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thank you George, good to info to learn, did not know that
 

ruger1980

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L4310 w/La682, L225
Oct 25, 2020
237
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CNY
Of course, I don’t know about YOUR particular machine..but mine operates like this:

The hyd pump output is directly proportional to the engine speed because the pump is directly bolted to the flywheel. The amount of fluid directed to the hydraulic-drive-motor is regulated by the speed lever/pedal (because it controls the swash-plate and therefore the pump piston-travel)... and any excess flow not utilized by the drive-motor bypasses it and passes thru the oil cooler before dumping back into the reservoir.

If low engine speed is used then less “excess” fluid is sent thru the cooler because more fluid is required by the drive motor for similar speeds.
That's not exactly how it works on the larger HST's with a cooler. The oil flow that propels the machine is in a closed loop, meaning the oil flows from the pump to the motor and back to the pump to be sent back to the motor again and again. During this process you will have leakage past the valve plate, pistons and at the slipper feet. This oil leaks into the HST case.

You have a charge pump which supplies makeup oil to replace this oil that has leaked from the closed loop. The charge pump oil is introduced to the low pressure or return side of the closed loop. The charge pump depending on the system also supplies servo oil to actuate the servo which controls the swash plate. Whatever oil from the charge pump that is not used by these functions goes out the charge pressure relief valve and into the HST case.

Basically all the oil that is pumped by the charge pump is sent through the HST case in one path or another and out the case drain port to the cooler and back to the transmission case.

As stated the smaller units do not have a cooler and rely on air flow or the housing for cooling. That is why it is very important to make sure the housing is clean.

Also hydraulic systems should be at a minimum of 160F operating temperature. Normal operating temperature should be about 180F up to 200F.
 

lynnmor

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Equipment
B2601-1
May 3, 2021
620
422
63
Red Lion
Aside from the heating discussed above, there is the fact that the rotating parts such as gears and shafts will necessarily need more torque applied to them as the RPM is reduced in order to do the same amount of work.
 

lmichael

Active member

Equipment
Kubota G2160
Apr 23, 2021
246
94
28
Rockford IL area
No it's not "new" and near as I can tell no pollution BS. Just a good ol' mechanical injection pump and injectors. It runs very well and does seem to run a bit hotter than my old Honda 4514 did. But certainly not overly hot. I typically "warm" it up for a few minutes before putting it to "work". Partly because I like the "music" it makes while idling LOL