Kubota l2501 throttle adjustment screw.
- Thread starter Rdrett
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i would also turn up the mechanical fuel pump (just like the older semi trucks) roll coal, and turn the throttle up some... no worries. don't let all the p.c. people stop you.
You can bet that Kubota didn't just blindly set the rpm range out of the blue. I'm sure it has thousands of hrs worth of testing on a dyno as well as real world testing. I don't know where it is but I'd bet they have a test and development facility where everything is put thru it's paces so problems can be found and corrected. All the big boys have them.
That said, the rpm range (pto speed) of each engine has been set for maximum hp, torque and efficiency. Changing that trying to gain power most likely will hurt more than it helps because you'll be getting out of the power band so to speak.
Running WOT has to be over revving the pto which puts more strain on your implement.
Having to adjust to faster ground speed to lower the pto speed is putting more strain on the engine, trans, tractor pto and implement driveline.
Brings to mind a friend who tried to pull a corn chopper and silage wagon with a 105hp Ford. Had to run WOT all the time to operate it and was straining the guts out of the tractor. Constant problems and wasted time. Changed up to a 180hp JD and never had any more issues.
Just going by you description you need one of two things:
Smaller implement or bigger tractor.
But like you said it's your tractor and equipment so do with it as you please. Happy tractoring.
That said, the rpm range (pto speed) of each engine has been set for maximum hp, torque and efficiency. Changing that trying to gain power most likely will hurt more than it helps because you'll be getting out of the power band so to speak.
Running WOT has to be over revving the pto which puts more strain on your implement.
Having to adjust to faster ground speed to lower the pto speed is putting more strain on the engine, trans, tractor pto and implement driveline.
Brings to mind a friend who tried to pull a corn chopper and silage wagon with a 105hp Ford. Had to run WOT all the time to operate it and was straining the guts out of the tractor. Constant problems and wasted time. Changed up to a 180hp JD and never had any more issues.
Just going by you description you need one of two things:
Smaller implement or bigger tractor.
But like you said it's your tractor and equipment so do with it as you please. Happy tractoring.
Understand but the problem with the l2501 is the 2050 rpm rated PTO speed.
I actually run mine a little faster at 2100 rpm wich is still within the pto speed range.
2400 is the max rpm under no load and under a light load the max rpm is 2200 and what the l2501 rating is.
So we are only talking about 100 rpm for engine “lug” (don’t know if that is the technical term).
I usually like to lug the engine down by a couple hundred rpms. There is no range there it almost like the engine is running with very little load.
The very small 100 rpm operating window is just not enough.
I need at least 300 rpm “lug” to put a little bit more load on the engine.
“Luging” down the engine a couple hundred rpm with be hardly any load on the engine.
This above is what I was trying to say the whole time but just figured out how to explain it.
Kubota L2501
Max RPM 2400 no load.
PTO working RPM with light load 2200 RPM.
PTO rated RPM 2050.
Only 150rpm “working” range.
“Bogging” down the engine 100-150 rpm is hardly any load.
A couple hundred more RPMS is exactly what the l2501 needs.
I bet the kubota will run for a long time where it PTO operating range makes it impossible to run anywhere close to loading down the engine. Also the fact it runs at very low rpm. And to top it off it is not chocked down with ANY emissions crap at all.
The max rpm for the engine in the l2501 is 3050 rpm according to the service manual for the d1703 engine installed in the L2501.
I am pretty confident in turning up the rpm to 2800 rpm and possibly 3000 rpm depending on testing.
The fact someone else turned theirs up to 3000 and hasn’t reported back any negative effects makes me more comfortable doing this.
Like I said I won’t be running it very often wide open throttle.
Out of the 110 hours I have used it probably 80 hours has been at idle. 25 hours 1/2 throttle and 5 hours full throttle. So very little time will be spent over 2400 rpms.
An L2501 HST.
The transmission will be the fly in the ointment. Increased RPM on the main shaft will connect to the traveling drive through a variable displacement pump. The HST has set check and high pressure relief valves, a charge relief valve, and a case valve. These valves limit the power transmitted through the HST.
Increased RPM to the pump will increase the temperature of the hydraulic fluid. Additional temperature increase will occur by the orifice effect of the fluid moving through the valves.
The PTO is geared to the engine so it will increase RPM with the engine. However, I would not expect much gain.
What I would suggest is looking at the WSM under Transmission which has the temperatures and pressures for an off-the-shelf machine. Measure before and after your mod. Then you will have hard data if heating the hydraulic fluid above spec.
The transmission will be the fly in the ointment. Increased RPM on the main shaft will connect to the traveling drive through a variable displacement pump. The HST has set check and high pressure relief valves, a charge relief valve, and a case valve. These valves limit the power transmitted through the HST.
Increased RPM to the pump will increase the temperature of the hydraulic fluid. Additional temperature increase will occur by the orifice effect of the fluid moving through the valves.
The PTO is geared to the engine so it will increase RPM with the engine. However, I would not expect much gain.
What I would suggest is looking at the WSM under Transmission which has the temperatures and pressures for an off-the-shelf machine. Measure before and after your mod. Then you will have hard data if heating the hydraulic fluid above spec.
I wouldn't put much stock in that, 2 of his 3 posts are in that one subject. He could have destroyed his machine, and been too embarrassed to come back and let the community know. It could be working flawlessly too though. I wish he'd report back with some follow information.
Also, he never mentions if he has a gear shift L2501, or an HST unit.
Rdrett, I have been following this thread with interest, I also have an L2501, please keep us updated on your progress. I have hot rodded pretty much every machine I have owned from motorcycles to cars, trucks and boats. Some worked out good, some didn't.....but it was always fun!
If this modification works out it looks like an easy way to pick up a few HP ad thats always good!
Fueling parameters generally are what affects diesel horsepower. Take the 5.9 Cummins that Dodge used in the early pickups. Before the Dodge application, the 5.9 was only about 135 hp at 2400 rpm. The engine that got put into the truck started out as a 160hp then 175, then 210. What changed, the injection pumps, delivery valves in the injection pump and injectors and probably some different timing, same engine same RPM. As was said about the electronic engines, they squeezed a lot more hp out of the same displacement. My 2007, 5.9 dodge with electronic fuel injection HPCR stock rated is 325 hp at 2600 rpm. Over twice the hp with fueling and in my case, a 24 valve head and that HP is with a smog cam.
So your tractor might have been derated with a different fueling mapping and smaller fuel injection. You might gain some hp by raising the governed speed but you do so at risk to what evr is the weakest link is. I agree with Wolfman that you cannot over-speed a hydraulic system without consequences.
You said in some previous thread that this thread was dead and that you would go somewhere else to ask the question. Do you want someone somewhere else that doesn't know hit butt from a hot rock to tell you sure it will work? I say GO FOR IT! Completely remove the top RPM governed speed bolt and see what it gets you! Maybe the little bugger can hit 4000 rpm. When the Dodge diesels came out, EVERYONE was looking to see how to get more horsepower out of the 5.9 Cummins. Some succeeded and some didn't with catastrophic results. The famous saying to the dreamer was "You are your OWN warranty station".
By the way, On my B3200 with the V1505, My PTO/540 rpm is around 2100. I am able to run all my PTO implements at a lofty 1800 to 1900 rpm, working hard and never touching the throttle. Maybe your governor in the pump has issues?
So your tractor might have been derated with a different fueling mapping and smaller fuel injection. You might gain some hp by raising the governed speed but you do so at risk to what evr is the weakest link is. I agree with Wolfman that you cannot over-speed a hydraulic system without consequences.
You said in some previous thread that this thread was dead and that you would go somewhere else to ask the question. Do you want someone somewhere else that doesn't know hit butt from a hot rock to tell you sure it will work? I say GO FOR IT! Completely remove the top RPM governed speed bolt and see what it gets you! Maybe the little bugger can hit 4000 rpm. When the Dodge diesels came out, EVERYONE was looking to see how to get more horsepower out of the 5.9 Cummins. Some succeeded and some didn't with catastrophic results. The famous saying to the dreamer was "You are your OWN warranty station".
By the way, On my B3200 with the V1505, My PTO/540 rpm is around 2100. I am able to run all my PTO implements at a lofty 1800 to 1900 rpm, working hard and never touching the throttle. Maybe your governor in the pump has issues?
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Anyone reading this do not raise the rpm over 3000 that is max rpm according to the service manual.
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I will let you know.
I am going to do a lot of testing before I publish the results.
I have been keeping an eye out for a pto dyno and hoping I can find one for this project.
Probably be like Joel in the thread mentioned above, never to be heard from again.
My guess is he had some catastrophic problem and didn't have the intestinal fortitude come back and admit his results.
My guess is he had some catastrophic problem and didn't have the intestinal fortitude come back and admit his results.
Insults to a guy online you’ve never met only because he did something you don’t agree with?
Maybe the first time he reved the engine up to 2800 rpm, 200 rpm below the d1703 spec it grenaded, blew up into a 1,000 pieces and killed him?
Maybe!
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North Idaho Wolfman
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You service manual must be way different that the thousands of other ones out there!
Yes I can find other manuals that show other specs.
BUT...They are different engines!
The only specs that matter are on a D1703-M-DI-E4-LB1 Tier4 engine.
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That is not from the service manual for the kubota d1703 engine.You service manual must be way different that the thousands of other ones out there!
Yes I can find other manuals that show other specs.
BUT...They are different engines!
The only specs that matter are on a D1703-M-DI-E4-LB1 Tier4 engine.
Kubota only makes one d1703 engine.
Are you saying that the d1703 engine in the kubota L2501 is not a d1703 engine?
I already posted specs for the d1703 engine.
He's saying that the specs of the other 'off shoots' of the d1703 engine, do not matter, because it's not the same specific d1703 (-M-DI-E4) engine that's in your CUT.
North Idaho Wolfman
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Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
That is from the L2501 WSM which includes the D1703-M-DI-E4-LB1 Tier4.
Post what WSM manual # you are referring to?
Not an insult, just a fact! Did I say anywhere I didn't agree with him, nope that's in your imagination?
We're talking two different animals.
One is a d1703 engine sitting by itself, with engine specs by itself.
The other is an L2501 system, with a d1703 powerplant. The powerplant in the L2501 system is rated by design to 2200rpm. Apparently there are other subsystems in the L2501 which will not tolerate an engine running above 2200 rpm.
One is a d1703 engine sitting by itself, with engine specs by itself.
The other is an L2501 system, with a d1703 powerplant. The powerplant in the L2501 system is rated by design to 2200rpm. Apparently there are other subsystems in the L2501 which will not tolerate an engine running above 2200 rpm.
Kubota only make ONE d1703 engine.
The M means nothing important.
The DI means direct injection.
The E4 means teir 4 engine.
Kubota only has one d1703 engine. They do not make a special d1703 just for the l2501.
Here is some information on what the rest of the engine model number means.
https://youtu.be/F1x_vNjXC-g
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