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Discussion Starter · #1 ·
I was debating for a long time whether it's worth it making this post but here we are prompted by latest TTWT video.

A beautiful custom setup with this mower and with laser box blade those 2 are something special.
However it was mentioned that tractor seemed happier PTO rpm wise when at slightly lower engine rpm. I very rarely use full rpm on my tractor and any other diesel equipment. There are several reasons why.
Firstly diesel engine usually provides maximum torque and power at much lower rpms when compared to gasoline engine. This is the same for engine in our 4052R which I will get back to later.
Passive regen is one hell of a mystery on these machines but from what I read it happens when engine is working in its optimal power window. From what I observer over hundreds hours of field work is that passive regen usually happens around 2100-2200 engine rpm when using taxing implement. Think mowers, baler, ground engaging stuff. When using higher rpms sooth build up was higher when compared to using lower rpms than 2100.
Lastly every time I we were given guidelines by our dealer on how to operate any implement we were always told to keep engine rpms in moderation. From my experience there is really no need for pushing 540. I have not noticed any difference while mowing, tilling, baling, wood chipping,... We even have some implements that suggest running specifically at 450 PTO rpm, not higher, that translates roughly to 2100-2200 engine rpm range.

When our tractor was at dyno what I really wanted to see was the torque and power curve. Here is the partially translated version with some personal information removed but should be sufficient to further my case.
Rectangle Slope Plot Font Parallel


4052R stock engine is represented by dashed line. As can be (not so clearly) seen maximum power is available at roughly 2100 engine rpm.

I am using this post mainly as callout to @Tractor Tim . Would it possible to show these power curves from your dyno measurements? Comparison of both stock and turbo 1R engines might have drastically changed them as well. (Using this method as I hope it will work unlike YT comments and might be beneficial for others.)
I would also like to see dyno power and torque curves of other models and engines if you guys have them available and anything else that might be added to this topic.

By no means I am saying that these engine can not run at full rpm. I am simply suggesting there is basically no good reason to do so.
 

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Discussion Starter · #8 ·
Mowers are designed for 540rpm input, they may work ok at a lower rpm but won't have the same blade tip speed. If you are using a tractor at the upper hp range of an implement you won't notice using lower rpm as much as a tractor with the min hp.

I remember reading years ago that you want a torque rise when a tractor runs out of power and the rpms drop. You want a higher torque at a lower rpm than you are running so when it bogs down you actually get more power. If not you would have to start downshifting like an 18 wheeler going up a hill, if you're tilling you want to keep your speed up to get through soft ground not slow down.
I definitely did not notice any difference in cut either with flail mower or disc mower. In heavy or normal grass. We have brush hog but currently its out of commission. But I definitely ran it at 450rpm and there was not anything to complain about with final cut. (There was later but because blade was as sharp as a ball.) For me it feels like tip speed is only important when lawn quality cutting is required so just finish mowers.
Our gas Z545R I run at wide open quite often but linear power increase typical for gas engines is really noticeable on that one.
 

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Discussion Starter · #9 ·
We had a 240D Benz for 25 years. Believe you me that it needed max rpm many times, especially in 1st and 2nd gears. Otherwise, with 65 hp, you don't move very fast. My wife could actually outrun most vehicles across town in it. It would make it fine going up Afton Mtn west of us on I-64 if you could maintain speed above about 65 mph. Drop below that, and you're down to 3rd gear and cannot shift to 4th because the maximum is 55 mph. The engine needed maximum hp to get over the mountain at speed.

However, the tractors are different. I needed max rpm on the 18.5 hp JD 4010 a lot of the time, but do not need the huge amount of hp in either the 1025R, 2025R or the B2601. Usually run those at 450 rpm PTO speed on both brush hog and wood chipper. These work fine at these lower rpms.
That to me sounds more like engine being not adequate for vehicle weight. That is a problem with almost every single car being sold in Europe now. With measly 1.0 or 1.2l engines to pull 2tons of weight. Ridiculous. I assume that benz engine had turbo if not that was the problem.
 

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Discussion Starter · #10 ·
So 53.6 HP or 54.4 PS. Pretty good I'd say.

The attached came from a Ecotune video so take it for what is wortha. Also attached is a Yanmar chart for a 4TNV86-CT. Not sure if that one helps.
As I said dashed line is the stock engine so ~36hp on the pto. Other stats are for slightly different measurement. Thats for something else not yet ready to post.
 

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Discussion Starter · #16 ·
I agree with @mo1 to run the tractor at PTO speed for those implements that need it. The reason is that is how the implements are designed to run, if you run at 450rpm you are running 17% slower. When in heavy grass, 3' to 5', you will want to be at 540rpm and can bog down in heavier spots.

Like I said in post #5 you want the rpm to above the maximum power because the governor alone is going to do the job, you want more power available at a lower rpm so you don't stall.

If you have a 4052R you can get an economy PTO kit for it which lets you run an implement at 540rpm at a lower engine rpm
View attachment 854756
I have that kit on order since approximately may 2021. I would love to finally get it but it seems JD is just totally ignoring it.

When I use 450rpm pto while mowing only slight bogging down occurs even in heavy wet thick grass. When I use higher rpms engine bogs down much more. I tried side by side cuts with no difference in final cut and mulching.
 

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Discussion Starter · #17 ·
As @Vern3039r said - The implements are designed to run at their designed speed.

It was mentioned above that diesel engines "generally" make the most torque at lower RPM. Something to consider - The engines are selected/designed/engineered for their specific use case in the device they are mounted. Thus the PTO speed of 540 on a 1 series is 3200engine RPM, but a 4052 has a much lower engine speed at 540PTO.

These engines and their mated transaxle have been engineered to operate in their designed operation window and it would be silly to think that running in the specific window it's designed to run in for is bad for it.

By the same logic, running a large displacement tractor trailer engine designed to run between 1200-1500RPM at 1000RPM would be "better" cause diesels generally make torque at lower RPMs. Engine design determines its best operating window and its relative to the engine use case.

I mow at WOT, so when the load (mower blades and drive) exceeds available power, the blade tip speed remains high. How you run your equipment- That's up to you 😁
I do not think that running at designated 540rpm is bad. Ofc I know that the whole tractor was designed around that. But I still do not understand why the most power is not provided at that or around that rpm range.
Also why passive regen does not happen at that range but instead sooth build up is increased.
 

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Discussion Starter · #22 ·
tractors and implements were designed to be run at certain RPM's just do it.
But why? If lower rpm does the some jobs activates the passive regen and lastly if feels like its more fuel efficient. I will hopefully confirm that one when TractorPlus adapter finally arrives.
And I definitely do not believe that tractor and implements are designed just to work properly at one single rpm. Spare the generator that was mentioned.
As I said we have few implemets that are designed to work at 540 but especially state that there is no need for that high of a rpm for them to work properly and as intended.
 

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Discussion Starter · #25 ·
I do notice a reduction is cut quality using a drum mower in heavy material if I don't run right up at speed. The drum mower, like a disc mower relies on very short blades pivoting on an axis and if the speed isn't fast enough the blades will not cut full width. Normally I can run a little under PTO speed but not in heavy material.

The other time that PTO speed really matters is with our tedder. I don't necessarily run at 540 PTO but match pto speed to the material to get the spread I want. That may be as low as 400 pto or it might be right up at 540, it just depends on the material.

I don't like running a 540 implement over 540. I'm sure they can take a little overspeed but prefer to not find out.
Now that is interesting as our tedder is one of the implements that wants relatively slow rpms and manual says that it is not advisable to run at 540 as it wont work properly. I guess either different tedding mechanism or gearing then.
Using our disc mower and before drum mower (basically the same) I never noticed any difference in cut quality or capacity. What most affected capacity was speed. But I could not go any faster even with higher rpms without bogging down to the same rpm.
 

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Discussion Starter · #26 ·
mowers, blade tip speed for nice cut
tillers, tine speed for grinding dirt fine
Engineers did not randomly pick numbers to put on implements, there is good reason behind them. We may not understand why but there is.
Also it has to do with fluid flow in the hydrostatic pumps on the tractor itself. It is not good to run them slower and reduce oil flow.
This is another area that can be beat to death for everyone that successfully follows the directions there is one that does not and never has an issue. Is it extremely important probably not.
I bought a Monza 2+2 4 cylinder back in the 70's. I NEVER put new oil in that engine, I used the oil I drained from my tow truck. That car ran like a watch up until, 285,000 miles, when I hit a curb in an ice storm and bent the unibody. So is new oil really all that important ?
this is another case of IMO
just because you can don't mean you should.
I agree with finish mowers or any other lawn mower to achieve nicer final look. But I did not notice anything with a tiller. The difference that tractor speed and especially rear chute made was significantly more noticable. Difference that pto rpm was not discernable in person or on the close-up pictures I took for comparison.
JD technicians also did hyd. flow testing and from ~2000 to wot there was only tiny marginal increase in flow.
In the first place it was them who instructed me not to use wot unless absolutely necessary with howering between 2-2.5k being the ideal for this tractor and engine.
Engineers pick numbers in transmissions of the implements as 540/1000 are standards for rear PTO I do not think there are actually many implements that run specifically at those rpms.
 
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