safe engine rpm "window" difference gear vs hydro

[madmax12]

Did a search, first. Did not see this exact topic discussed. I apologise if it has been beaten to death before. I can't find it.

Bought an HST in May 2012.

Dealer said rpm operation up to my choice. If doing heavy work, keep rpm near highest operation levels. If doing light work, it would do no harm to operate a little above idle...and low rpm is to my advantage, as it would consume less fuel. Less fuel and noise level would be the only reason I would like to operate at lower rpm.

Obviously, if mowing, PTO operation dictates engine rpm, as I have only one PTO speed option - 540...rear finish mower.

But if I'm moving a light pallet, or slowly driving with an empty bucket (pick your own version of some light duty task), is there any problem operating near engine idle or slightly above?

Why I ask...

Yesterday, another (more experienced) dealer said a gear version could operate at low rpm, saving fuel. But an HST should always run at PTO speed. Low rpm on HST would be bad for pump, flow, etc.

I don't really know anything about all of this. Can someone with a real understanding explain?

Thanks

 

[heviduty]

I wouldn't worry about puttering around doing light work at just above an idle unless it's really cold or you do it for a long time. From what I understand, the only reason to keep the rpm's up when not using the pto, or not working it hard, is to keep the engine temp up (which prevents carbon buildup), which could be a concern in your area in the winter. Our local dealer recommends not running less than 1500 for long periods.

 

[madmax12]

I wouldn't worry about puttering around doing light work at just above an idle unless it's really cold or you do it for a long time. From what I understand, the only reason to keep the rpm's up when not using the pto, or not working it hard, is to keep the engine temp up (which prevents carbon buildup), which could be a concern in your area in the winter. Our local dealer recommends not running less than 1500 for long periods.

Your advice matches the operator's manual. It has the same warning for cold weather. However there is no info to indicate any difference/danger with gear vs hydro rpm operation. Thank you for your reply.

 

[heviduty]

Your advice matches the operator's manual. It has the same warning for cold weather. However there is no info to indicate any difference/danger with gear vs hydro rpm operation. Thank you for your reply.

I would interpret that as "no difference".

 

[94BULLITT]

My 4240 has a auto throttle advance so I almost always use it. My bx and the bobcat I had seem to operate good at 2000-2200 rpm. The hydro is not as responsive at idle or a low rpm. Sometimes on the bx I put the hydro pedal to the floor and control my speed with the throttle. I don't think carbon is as big of a deal with ULSD fuel,

 

[Gary Fowler]

When roading my B26, I run it pedal to the floor and what ever RPM needed for speed. I see no need in reving the engine to 3000 RPM to go 5 MPH when 1200-1800 is plenty. My B26 idles higher (1200) than my LS (900) which maybe is due to the hydrostatic in the B26. I rarely run the Kubota at max rpm for anything as it just seems like it is running too fast and much too noisy. 2400 RPM or less works for back hoe work which is about all I do with it. FEL work, the rpm comes down to about 1800 and it has power to spin all the tires in 4WD without stalling the engine.

 

[madmax12]

I would interpret that as "no difference".

Unless someone teaches us differently, I'm inclined to agree with you.

 

[madmax12]

94BULLITT and Gary, thank you for your replies.

 

[crazyal]

I usually don't go too much lower than 1800. The fuel difference isn't much and I figure at 1800 there's lots of oil moving around plus there's plenty of power to move.

 

[TripleR]

I would have to just pretty much repeat what the others said, I run HST as well as gear and unless running something off the PTO as mentioned, run at the speed that gets it done comfortably though on none of my tractors is this "just above idle", usually no lower than about 1200-1500, but this may vary with different tractors/models.