Hydraulic functionality

dnw64 · Sep 16, 2018

I recall seeing a bunch of people complaining about the performance of Kubotas at low RPM. It may well have been regarding the BX series, as my my most recent tractor was a M-F GC series, which is a BX sized unit, so that's the direction a lot of my research went.

I have to say I have been singularly impressed with the performance of my B3030. Whether of the loader, 3-PT or (Woods) BH, there is NO DEFICIENCY in the hydraulic system. It's been my un-scientific observation that I have near the same force available (whether lifting or pressing with the bucket, lifting with the 3-PT or ANY of the BH functions) at an idle as Full Throttle. The only difference I notice at idle* vs higher throttle is Speed, not Power.

Just curious - is this pretty normal? I have virtually no experience... When I mentioned it to my son-in-law, who has had a couple excavators (one Kubota, on BobCat) in his small side-business, he thought it was pretty much par for the course. Just feels weird to me, coming from an automotive background.

*I rarely try to do anything at an idle, but 1200-1500 RPM is quiet and very functional. On the rare occasion that it doesn't do what I want to do, raising the RPM almost never makes any difference.

jeff9366 · Sep 16, 2018

All brands of tractors:

Some do not grease, increasing friction. Dealers encounter loaders immobilized.

Some buy cheap hydraulic fluid based on cheap oil with few/no performance additives.

Some do not change hydraulic fluid nor filters for years.

Some get an unintentional low-fill from dealer, but never check fluid level for themselves.

majorwager · Sep 17, 2018

Jeffy

Not clear what point you are attempting to make?

Grandad4 · Sep 17, 2018

dnw64 said:
I recall seeing a bunch of people complaining about the performance of Kubotas at low RPM. It may well have been regarding the BX series, as my my most recent tractor was a M-F GC series, which is a BX sized unit, so that's the direction a lot of my research went.

The BX is the one known for needing the engine revved up. For whatever reason Kubota designed the BX so the hydraulics don't really get much fluid until the engine rpm's are up more than halfway. Some seem to object to this characteristic, but personally, it has never been an issue for me with my BX. Putt-putting around at idle was never my style, I guess.

LouNY · Sep 17, 2018

To the best of my knowledge most current factory open center hydraulic pumps are open center systems with gear pumps, unless a gear pump has excessive clearances the pressures developed are not dependent on rpm, however the volume pumped is.
If your system puts out 2000 psi you should see 2000 psi regardless of your engine rpm,
however your volume (gpm) is extremely dependent on rpm the faster it turns the more volume.

The volume is what provides the speed of hydraulic operations.

The pressure is what determines the max lifting ability.

oldnslo · Sep 17, 2018

Like Grandad4 states. The BX series uses a single pump with a priority flow control. The priority flow control takes most if not all of the pump flow for steering so the FEL & 3PH might not operate at idle. I believe this is the only Kubota series made this way.

I am not sure if any other other brands have a similar design on their equipment or not.