PSI/RPM curve for BX 25

[Dpm708]

Does anyone have a spec sheet or whatever relating to the Hyd pressure put out at any given RPM for the BX 25? And what would be relief spring pressure? Thanks.

 

[Stonehaller]

I think the BX25 relief pressure is about 1800 psi. The pressure will not vary with RPM, at least not significantly. The relief valve is not perfectly linear and you will see a small increase in pressure from low to max RPM.

The flow rate, however, will be proportional to the RPM. Think of the flow rate as velocity, i.e. how fast your cylinders will move. Think of pressure as force how much you can lift with you FEL.

 

[keyman1808]

I dont have the actual specs but I find that the FEL works good at about 1900 RPM on up. The BH likes 2800 RPM and higher but thats on my BX24.

 

[radioman]

I dont have the actual specs but I find that the FEL works good at about 1900 RPM on up. The BH likes 2800 RPM and higher but thats on my BX24.

I'm gonna agree with that. One thing you want to keep in mind- using too low of RPM with heavy work for slower precise handling, it can cause hydro captivations in the pump- (eek!) .

 

[Yankee Clipper]

DPM,

The BX25 hydraulic pump flow rate is 6.6 GPM at 1500 RPM - the first 2 gallons go to steering via the prioroity valve and you can not recover them as they go back to tank. That leaves you with 4.6 GPM to do whatever else on the tractor. Stonehaller is right that the flow is proportioinal to the engine RPM and you should throttle up if you want speed / increase in flow rate.

The relief pressure is 1778-1849 PSI - it is pilot operated so it will start to crack at about 90% of this pressure.

YC

 

[Inky05]

The pressure will not vary with RPM

...which then begs the question... why don't the hydraulics work at idle?????

 

[radioman]

...which then begs the question... why don't the hydraulics work at idle?????

like by BX24 in 50 series, it will not run in idle. there is some sort of safety feature where i must be 1600 rpms or higher for hydraulics to work. this was changed in the 60 series like bx25.

 

[CHDinCT]

Can't tell you what the psi curve is with rpm, but I believe it is relatively flat as Stonehaller states. I have checked my PSI with a gauge and it read right under 1800 psi but I don't recall what rpm that was at, BUT,

I had previously owned a JDX485 that spec'd out at 1000 psi. I ran a test on it with a pressure gauge and got 950 psi at idle and 1050 at full rpm, a mere 100 psi difference.

 

[Stonehaller]

...which then begs the question... why don't the hydraulics work at idle?????

My guess is at idle that all the pump flow is going to the power steering. At higher RPM there is enough pump volume for oil to be routed to the hydraulics.

 

[Nightforce]

BX25D

As you can see by the information below, there is a significant difference in pump output pressure at an idle vs the working rpm range. Do the math and see how this difference equates to force and lifting ability.

Hydraulic Pump Pressure

1500rpm



3000rpm

 

[prichard]

What about the curve? What pressures in between?

 

[Luke'sScreenName]

My MX4800 is the same way. Always makes me chuckle when someone regurgitates the TBN dogma that RPMs don't dictate hydraulic force.

 

[dodge man]

There are a couple of things at play here, pressure and volume. I'm not sure but at idle even if the pressure is enough to run the hydraulics, my guess is the volume isn't enough. I know on my BX the hydraulics prettty much won't do anything unless you bring the engine up off idle to maybe 1800 rpms. Of course this thread is 6 years old also, but still relevant.

 

[Luke'sScreenName]

What about the curve? What pressures in between?

Here is the data points for my MX.



And a few hundred PSI make a much bigger real-world difference than one might think....

 

[David_Kb7uns]

For the first 1/4 to 1/3 throttle ALL hydraulic flow goes to power steering and charge pump circuit with barely any flow going to loader and then 3 point hitch.

Once you get flow above the flow required by the power steering you will start to see movement on the loader and 3 point hitch.

David

 

[Luke'sScreenName]

For the first 1/4 to 1/3 throttle ALL hydraulic flow goes to power steering and charge pump circuit with barely any flow going to loader and then 3 point hitch.

Once you get flow above the flow required by the power steering you will start to see movement on the loader and 3 point hitch.

David

That is not the case with either of the kubota's with loaders I have owned. :confused3: maybe I'm misunderstanding.

 

[4570Man]

That is not the case with either of the kubota's with loaders I have owned. :confused3: maybe I'm misunderstanding.

Our tractors have separate pumps for the steering.

 

[David_Kb7uns]

That is not the case with either of the kubota's with loaders I have owned. :confused3: maybe I'm misunderstanding.

Yes you are misunderstanding, my L3130 has a 2 section pump. First section is power steering and GST transmission supply, second section is implement/ loader.

Some of the larger Kubota TLBs have a third section for the backhoe swing.

David

 

[Luke'sScreenName]

Our tractors have separate pumps for the steering.

Sure. I assumed the BX25 had 2 pumps also... That's what I get for assuming.

 

[DK35vince]

My MX4800 is the same way. Always makes me chuckle when someone regurgitates the TBN dogma that RPMs don't dictate hydraulic force.

Lifting something to heavy and my loader will go into relief at idle, increasing RPM's makes little to no difference in lift power.