Full RPM or high idle? Bush hogging fuel efficiency

[radioman]

well lets see - the advice to use tractors at rated speeds- seems to have larger tractors - no offense guys. For those who have a compact or subcompact tractors to run at lower engine speeds starts to become a gray area I think. Look at it this way - the smaller the HP engine has the less pto HP there is and the greater chance of wear due to untold stress on engine or the tractor pto parts. The thing is we dont have a real world test of two identical tractors running same time in similar stuff doing jobs and one at lower engine speeds and other at rated engine speed. Then do a teardown amd show results. Thus the reason why we continue to have this age old debate of run tractor at rated speeds or not when working with tractor.

JDgreen - rated engine speeds is the engine rpms needed to achieve the FULL PTO speeds. It doesn't matter if it a mid or rear pto - for most of the time its always for the rear since nearly all tractors have them.

My opinion? LOL. I
usually run near rated speeds but for some jobs I run slower engine speeds for the desired effect of slower speeds. For example my rated speed is nearly 3200 rpms and When I mow I mow at 2800-3200 depending on grass thickness. When I was mowing down the garden plants that is done for the year, I ran it at 1200-1400 since I do not want the plants to be spitting out of the chute but rather lay there. When I run the Backhoe- I might run 1600 if I feel I am in delicate spot of digging then run at 3200 when digging is good, get job done quickly.

IMHO Run the tractor any way you want... it your tractor and do it what suits you.

 

[TripleR]

well lets see - the advice to use tractors at rated speeds- seems to have larger tractors - no offense guys. For those who have a compact or subcompact tractors to run at lower engine speeds starts to become a gray area I think. Look at it this way - the smaller the HP engine has the less pto HP there is and the greater chance of wear due to untold stress on engine or the tractor pto parts. The thing is we dont have a real world test of two identical tractors running same time in similar stuff doing jobs and one at lower engine speeds and other at rated engine speed. Then do a teardown amd show results. Thus the reason why we continue to have this age old debate of run tractor at rated speeds or not when working with tractor.

JDgreen - rated engine speeds is the engine rpms needed to achieve the FULL PTO speeds. It doesn't matter if it a mid or rear pto - for most of the time its always for the rear since nearly all tractors have them.

My opinion? LOL. I
usually run near rated speeds but for some jobs I run slower engine speeds for the desired effect of slower speeds. For example my rated speed is nearly 3200 rpms and When I mow I mow at 2800-3200 depending on grass thickness. When I was mowing down the garden plants that is done for the year, I ran it at 1200-1400 since I do not want the plants to be spitting out of the chute but rather lay there. When I run the Backhoe- I might run 1600 if I feel I am in delicate spot of digging then run at 3200 when digging is good, get job done quickly.

IMHO Run the tractor any way you want... it your tractor and do it what suits you.

We have SCUTS, CUTS, UT and what was considered Ag and we run them all the same from 23 HP to 85 HP.

Agreed run your stuff the way you want, even if it's wrong; tricky part is determining right/wrong. I imagine it is not a black and white situation but rather black/gray/white.

 

[Martian]

I think a lot of people are talking about fuel efficiency without considering the OP is talking about using a PTO powered implement. I have a lighter duty small brush hog because that's all that was required to keep my fields chopped down, I'm not doing the same type of clearing some of you are. So even though my brush hog is pulled behind a tractor that has 65 PTO HP, I only need 25-30 PTO HP. Even though I have all that power, if I run it at say 1600 RPM's, the fields will not cut as because of the slower blade speed. The PTO doesn't turn at a constant rate, only loosing torque, as you increase RPM's the revolutions per minute of the PTO increase as well. I wish I'd taken pictures but next time I'll run a field at low RPM and show you the cut quality vs PTO RPM. The ONLY time I ever run at PTO speed is using the PTO, otherwise you are just burning fuel. You can't tell the difference between running at 1600-1800 RPM's to PTO speed for loader work, but it makes a HUGE difference for PTO work.

 

[TripleR]

I think a lot of people are talking about fuel efficiency without considering the OP is talking about using a PTO powered implement. I have a lighter duty small brush hog because that's all that was required to keep my fields chopped down, I'm not doing the same type of clearing some of you are. So even though my brush hog is pulled behind a tractor that has 65 PTO HP, I only need 25-30 PTO HP. Even though I have all that power, if I run it at say 1600 RPM's, the fields will not cut as because of the slower blade speed. The PTO doesn't turn at a constant rate, only loosing torque, as you increase RPM's the revolutions per minute of the PTO increase as well. I wish I'd taken pictures but next time I'll run a field at low RPM and show you the cut quality vs PTO RPM. The ONLY time I ever run at PTO speed is using the PTO, otherwise you are just burning fuel. You can't tell the difference between running at 1600-1800 RPM's to PTO speed for loader work, but it makes a HUGE difference for PTO work.

Pretty much what I am talking about, I run engine speed to match the job and for PTO stuff that is PTO speed. Both my tractors indicate PTO revolutions on the instrument panel, so that is what I use. When breaking my 5740 in, I experimented a bit and could really tell the difference in the cut on my rotary cutter.

 

[Soundguy]

We have SCUTS, CUTS, UT and what was considered Ag and we run them all the same from 23 HP to 85 HP.

Agreed run your stuff the way you want, even if it's wrong; tricky part is determining right/wrong. I imagine it is not a black and white situation but rather black/gray/white.

( see.. we agree quite often.. )

ditto 100%

 

[kf4uda]

I have two rotary cutters, a 10ft and a 6ft. Each is designed to operate with a pto input speed of 540 rpm. I run the tractor's engine speed at whatever is required to obtain the proper pto speed. As said by TripleR, pto speed is marked on the tach. The tractors were designed to do this. I use the transmission to change ground speed. I do not have a CUT at this time but if I did, I would operate it the same way.

 

[Marveltone]

My personal take on this, matched with my own experiences seem to fall in line with Soundguy and TripleR. When using PTO equipment, especially mowers and cutters, I run at the rated PTO speed to keep the blade speed up, as well as enough power to do the job. My tractor is pretty small and has just enough power to punch through the heavy stuff, so I see no reason to handicap it further. I also suspect the engineers who design these machines have at least a vague idea what they're talking about, regarding what works for each particular model.

When running the loader, I give enough RPM's to keep a good flow of hydraulic fluid going through the pumps; in my case, less than PTO speed, but way above a fast idle. This, of course, with any operating decision, is a personal decision and will vary depending on operators, machines and conditions.

Joe

 

[Soundguy]

When running the loader, I give enough RPM's to keep a good flow of hydraulic fluid going through the pumps; in my case, less than PTO speed, but way above a fast idle. This, of course, with any operating decision, is a personal decision and will vary depending on operators, machines and conditions.

Joe

i agree as well. when i'm going loader or backhoe work.. rpm is less than pto rpm... IE.. what's needed for good hyd flow.. etc..

 

[TripleR]

( see.. we agree quite often.. )

ditto 100%

Should we be worried.

 

[PapaPerk]

It all boils down to engine loading and output efficiency. You certainly do not want to bog the engine. However if the PTO chore is light, there is no reason to run the machine at full throttle... or anything close.

An operator must use experience when operating a tractor... listen to the engine or watch the tac when the bushhog etc begins to load the tractor. Keep the engine running at a throttle setting where it's not bogging the engine but also not racing it. Like I said this requires some "knack". And is why manufactures say to run the machine at 500 rpm, etc. That's a good general recommendation to follow for inexperienced operators.

If you are running in a high load situation like very heavy grass or roto tilling... then you run at max rated PTO speed for implement... and then slow tractor ground speed till engine is not bogging. Again... this takes a bit of time and experience to learn. You certainly do not want to bog the engine! Keep the revs up. However if the mowing, etc is easy then you can back the throttle off to save fuel, reduce noise and wear/tear.

Have fun! :thumbsup: