Working Engine RPMs

[gunmonkeyintl]

Sorry in advance if this comes off as a stupid question, but where do you guys set your engine RPMs when doing various tasks?

The manual's broken Engrish wasn't very helpful, other than it explained the PTO RPM setting, and noted that I shouldn't work it "hard" during the first 20 hours, but didn't really give an indication of what "hard" is.

My backhoe has a label on it suggesting 18-2100 RPMs and, other than the PTO mark on the tac, that is the only reference I have on sane RPMs. Are there instances where the throttle should be all the way open? What do the RPMs go to with the throttle all the way open? Should I avoid that during break-in?

For the time-being, I have been running the back-hoe at 1900, and have been staying at or below that speed for all other tasks. I'll likely keep with that at least to 20 hours, but would like some reference for the future.

 

[Gary Fowler]

Not sure about your tractor but most break-in procedures recommend not running the engine at the same RPM for extended periods, so vary the rpm as you work. Strange that your book said to work it easy, my LS manual said to run it fully loaded for break-in. Of course I didn't have anything to load it fully with so I hooked on the box blade and using that and the FEL, dug a small pond in the first 10 hours loading it to spin the wheels and varying the RPM up and down using the foot throttle. Locked in speed was set at 1500 minimum and I would occasionally rev it to the max for a few seconds when travelling.
As for running speeds, it shouldn't hurt the engine to run it full throttle as they are designed to do that. I rarely run my Kubota B26 at full throttle although the 540 rpm speed is only reached at wide open throttle(WOT). When using the back hoe or FEL,(which is about all I use it for) I find that 2000 RPM is a comfortable operating speed and the engine noise is not that bad compared to WOT AND it has plenty of power at that speed.
I don't have any uses for the PTO on it so I never run it at high RPM unless roading it from one place to the other and even then it is pretty slow.

 

[DeereMann]

gunmonkeyintl, most any type of reciprocating engine break-in will not want you to run full rpm or full load for some period of time. In addition, per Gary Fowler, they also recommend you run at varied speeds and load for the first hours, maybe 10 hours.

What this does is a "final machining" of the engine wear points - camshafts, cylinder walls, gear teeth, etc. It prevents cylinder bore polishing, wiped camshafts, etc. It is true that the use of CNC machining now controls tolerances tighter, but wear surfaces still need a final run-in, as the manufacturer will not spend the time & money to do so - we would not pay for it.

Note too there is usually early oil changes to remove the machined cotaminants collected in the filters & suspended in the lubricating oils.

This is typical for most reciprocating engines, including automotive.

Hope this helps,
DeereMann
Mechanical Engineer
Major Engine OEM

 

[Gil Case]

Hst needs to run at 2100 when moving or so I was told by dealer.

 

[gunmonkeyintl]

gunmonkeyintl, most any type of reciprocating engine break-in will not want you to run full rpm or full load for some period of time. In addition, per Gary Fowler, they also recommend you run at varied speeds and load for the first hours, maybe 10 hours.

What this does is a "final machining" of the engine wear points - camshafts, cylinder walls, gear teeth, etc. It prevents cylinder bore polishing, wiped camshafts, etc. It is true that the use of CNC machining now controls tolerances tighter, but wear surfaces still need a final run-in, as the manufacturer will not spend the time & money to do so - we would not pay for it.

Note too there is usually early oil changes to remove the machined cotaminants collected in the filters & suspended in the lubricating oils.

This is typical for most reciprocating engines, including automotive.

Hope this helps,
DeereMann
Mechanical Engineer
Major Engine OEM

I get engine/machine break-in. Specifically, my question was regarding what RPMs were normal/sane for common operations (transit, FEL work, towing/pulling etc.), and are there cases where it is best to run at WOT, since the manual did not provide specifics other than PTO operation, and not to run it "hard" during break-in.

 

[gunmonkeyintl]

Hst needs to run at 2100 when moving or so I was told by dealer.

Did he give you any explanation on that? My lawn mower requires full throttle during movement because the HST cooling fan only runs with the engine at WOT.

Was the 2100 RPM a minimum for the hydro pump, or was it an absolute? I don't see why the engine RPM would be critical during transit. It seems like if you were happy with transit speed at idle (or higher, for that matter), then you are good.

 

[mikehaugen]

Did he give you any explanation on that? My lawn mower requires full throttle during movement because the HST cooling fan only runs with the engine at WOT.

Was the 2100 RPM a minimum for the hydro pump, or was it an absolute? I don't see why the engine RPM would be critical during transit. It seems like if you were happy with transit speed at idle (or higher, for that matter), then you are good.

He specifically said for mowing, so I would guess that was to have the proper pto speed, not anything to do with the hydro.

Ok nevermind... I re-read it and saw that he said "moving". I saw "mowing" the first time I read it.

 

[Sysop]

From my understanding of HST, anytime you hear a whine, it's not got enough fluid pumping to do what you ask. Most of the HST die-hards I've talked to say you want enough RPMs to move enough fluid that it's not whining (this varies per machine and what all you're doing with it at the time). The HST uses the fluid for pressure to move the machine, lubrication to keep things from seizing, and relies on GOBS of it moving through the system to keep things cool. When it whines it's cause there's not enough fluid pressure to do all of the things it needs to do, therefore when it's whining, it's getting too hot, not getting enough lube, all while not maintaining proper pressures to do what you want it to do.

In low gear I can move my HST around fine with 1200-1500RPM. Medium range I need 1600-1800 to move around without making it whine. In high range it takes 2000-2200 RPM to keep it from whining. In all ranges at these RPMs if I mash the go-pedal too far too quick I'll hear the RPMs dip and the HST whine, this is bad. If I'm trying to get something done quickly and am needing more response from the go-pedals, I increase RPMs rather than mashing on the go-pedals harder. Whining in an HST is more or less the geared equivalent to draining half your gear oil then grinding the gears while slipping the clutch, things will break if you keep it up.

 

[gunmonkeyintl]

From my understanding of HST, anytime you hear a whine, it's not got enough fluid pumping to do what you ask. Most of the HST die-hards I've talked to say you want enough RPMs to move enough fluid that it's not whining (this varies per machine). The HST uses the fluid for pressure to move the machine, lubrication to keep things from seizing, and relies on GOBS of it moving through the system to keep things cool. When it whines it's cause there's not enough fluid pressure to do all of the things it needs to do, therefore when it's whining, it's getting too hot, not getting enough lube, all while not maintaining proper pressures to do what you want it to do.

In low gear I can move my HST around fine with 1200-1500RPM. Medium range I need 1600-1800 to move around without making it whine. In high range it takes 2000-2200 RPM to keep it from whining. In all ranges at these RPMs if I mash the go-pedal too far too quick I'll hear the RPMs dip and the HST whine, this is bad. If I'm trying to get something done quickly and am needing more response from the go-pedals, I increase RPMs rather than mashing on the go-pedals harder. Whining in an HST is more or less the geared equivalent to draining half your gear oil then grinding the gears while slipping the clutch, things will break if you keep it up.

That certainly makes sense. But, it seems like anytime I creep along (with my tractor or my lawn mower) I get HST whine, regardless of RPM. If that is the case, then low ground-speed is hard on an HST in any event. Maybe I am missing something, or hearing a different sort of whine.

 

[murphy1244]

I am rarely am above 2000 rpm use 2300 for chipper shredder.