L2501 Modifications

drewzee87t

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Equipment
B2910 HST, Modern Sunshine RC, Gannon Earthcavator, Frontier 1150 Tiller
May 20, 2016
67
4
8
misery
I will PM you. I haven't figured out what the oil return looks like but I think TD03 for my 1.5 liter would be like going directly to a turbo upgrade and skip the stock turbo. I have a casting in the block at same spot where you put your oil drain. I don't know if that is a plug that pops out or if I have to drill, and that would require pull the oil pan and metal shavings. I hope it's a plug of some sort but it looks pretty solid on mine. I have the parts diagram from a b3350 which is my same motor with a turbo and it shows that same spot to be where they put the oil return. Let me know if yours was a plug or if you had to open it up yourself. The rest of your pics look awesome. I don't know if I can afford that nice of a kit :). Also good to hear it working well in testing.

Thanks
 
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greenacresnorth

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L2501,BH77
Feb 18, 2018
165
3
18
34
Morganton,NC
Thanks for the heads up! The pcv was the first thing I did since it will cause a massive boost leak the way it’s routed into the intake manifold. Also on all my turbo cars/trucks I re route the pcv to atmosphere. On the Kubota I just ran a new line down next to the block by the pan basically the way Cummins does it on the old 5.9 12 valve. I’ve already put about 20 hard hours with the turbo and haven’t seen any paint discoloration. The housing is probably around 3 to 4 inches away from the side of the hood. Looks closer than it is when you shut it. A turbo blanket wound be the best option but I don’t even know if they make one for a tiny tdo3 that’s internally waste gated 😂
I used a GT15, turbine housing housing is substantially bigger, i guess that is why I had clearance issues, infact I had to put 10-11 degrees offset in the turbo/manifold adapter to clear the hood all together. its funny though, we have never met or shared knowledge, yet our turbo layouts look almost identical!!!
 
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Mikemoto17

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L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
9
19
3
California
I used a GT15, turbine housing housing is substantially bigger, i guess that is why I had clearance issues, infact I had to put 10-11 degrees offset in the turbo/manifold adapter to clear the hood all together. its funny though, we have never met or shared knowledge, yet our turbo layouts look almost identical!!!
That’s awesome man!!! I purchased this tractor 6 months ago with plans to do this I really didn’t want the dpf and the price difference was crazy going up to 50hp. I did a lot of groundwork and even asked the Kubota mechanics at the dealer when I picked up the tractor if it shares the same pto, and HST gearbox as the l3901. Funny thing is they were looking at me kinda weird lol probably knew I was gonna modify it. Turns out it’s identical so I’m not worried about stressing anything out. The only difference really is the PTO output ratio. I did some clearing on my property yesterday and my tractor now chips 8 inch round pine trees like no problem with the turbo 😂😂 pic below with the temporary exhaust I threw together. It literally sounds like a mini Cummins. It spools up nicely at 1600rpms with no smoke under full load. I have the fuel screw out 2 full turns and bumped the timing up to 9 degrees. I’m only running it out to 2650 rpms currently.
 

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ccoon520

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L2501 w/ FEL
Apr 15, 2019
152
10
18
IA
Since my tractor is under warranty for a while still I won't be doing this soon but would you consider making/selling this mod as a kit with instructions? I was thinking about adding a turbo and upping the hp to my 2501 once the warranty expired but if a kit was available that would save a bunch of headache.
 

Nicfin36

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L2501 HST, BH77 Backhoe, QA Loader
Jun 19, 2019
356
61
28
Decatur, AL
Since my tractor is under warranty for a while still I won't be doing this soon but would you consider making/selling this mod as a kit with instructions? I was thinking about adding a turbo and upping the hp to my 2501 once the warranty expired but if a kit was available that would save a bunch of headache.

I'm also not planning on doing anything to mine until the warranty expires. Also, I am assuming an enterprising person will be selling kits by then. It would be pretty cool having a bit more hp.
 

Henro

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B2910, BX2200
May 24, 2019
518
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North of Pittsburgh PA
That’s awesome man!!! I purchased this tractor 6 months ago with plans to do this I really didn’t want the dpf and the price difference was crazy going up to 50hp. I did a lot of groundwork and even asked the Kubota mechanics at the dealer when I picked up the tractor if it shares the same pto, and HST gearbox as the l3901. Funny thing is they were looking at me kinda weird lol probably knew I was gonna modify it. Turns out it’s identical so I’m not worried about stressing anything out. The only difference really is the PTO output ratio. I did some clearing on my property yesterday and my tractor now chips 8 inch round pine trees like no problem with the turbo 😂😂 pic below with the temporary exhaust I threw together. It literally sounds like a mini Cummins. It spools up nicely at 1600rpms with no smoke under full load. I have the fuel screw out 2 full turns and bumped the timing up to 9 degrees. I’m only running it out to 2650 rpms currently.
I know that the running gear is the same as the larger tractors, but I wonder if increasing the HP developed by the engine is a concern?

Just a curiosity question, as if I would bite the bullet and buy a L2501 to add to my small fleet of two, I would not make the modification myself, as I do not think I need it.
 

old and tired

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L2800
Dec 8, 2019
278
49
28
Virginia
...but I wonder if increasing the HP developed by the engine is a concern?
L2501 is a de-tuned engine. Specs for L3400 and L2501:


L3400 - Kubota D1703 100.5 ci [1.6 L]
Bore/Stroke: 3.425x3.638 inches [87 x 92 mm]
Power (gross): 34.7 hp [25.9 kW]
Rated RPM: 2700

L2501 - Kubota D1703-M-DI-E4 100.47 ci [1.6 L]
Bore/Stroke: 3.4x3.6 inches [86 x 91 mm]
Power (gross): 24.8 hp [18.5 kW]
Rated RPM: 2200

Also, most things are also designed to be able to handle extra "stress". Same as the hydraulic system which can be bumped up - Yes, extra stress = possibility of damaging something.

Edit - added engine model number for L2501...
 
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Henro

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Equipment
B2910, BX2200
May 24, 2019
518
54
28
North of Pittsburgh PA
L2501 is a de-tuned engine. Specs for L3400 and L2501:


L3400 - Kubota D1703 100.5 ci [1.6 L]
Bore/Stroke: 3.425x3.638 inches [87 x 92 mm]
Power (gross): 34.7 hp [25.9 kW]
Rated RPM: 2700

L2501 - Kubota ??? 100.47 ci [1.6 L]
Bore/Stroke: 3.4x3.6 inches [86 x 91 mm]
Power (gross): 24.8 hp [18.5 kW]
Rated RPM: 2200

Also, most things are also designed to be able to handle extra "stress". Same as the hydraulic system which can be bumped up - Yes, extra stress = possibility of damaging something.
Interesting spec comparison.

I wonder if it is the same engine, with the specs rounded to make it look slightly different due to the break point for emissions being so close to the L2501's HP rating? Having read the L2501 engine is de-tuned, I have wondered what tractor uses the same engine in a higher HP version.

I understand from reading here at OTT that the L2501 shares the same mechanical drive line as the two bigger brothers, the L33xx and L39xx. So from that perspective your increased HP should not be a great concern.
 

ccoon520

Member

Equipment
L2501 w/ FEL
Apr 15, 2019
152
10
18
IA
Also, most things are also designed to be able to handle extra "stress". Same as the hydraulic system which can be bumped up - Yes, extra stress = possibility of damaging something.
They aren't so much designed to handle extra stress. They are designed with a Factor of Safety (good rule of thumb is 2 FOS but some go less some go more) to accommodate things like tolerance stack up and manufacturing defects, plus some consumer rough housing. This minimizes warranty claims and as well as accommodate for different environments (i.e. Higher or lower altitude). Also, a higher HP gain does increase the stress that the cylinders see but the killer would be if you can't keep the engine at the correct operating temp or if you over rev it.

If you put too much dome pressure from an oversized turbo with no blow off valve, most likely you'll blow a head gasket and break your head bolts but you probably won't grenade your motor. If you have a cooling system that can remove 400 Watts but you have it hooked up to one that makes 450 watts the thing will weld itself together.
 

Mikemoto17

New member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
9
19
3
California
They aren't so much designed to handle extra stress. They are designed with a Factor of Safety (good rule of thumb is 2 FOS but some go less some go more) to accommodate things like tolerance stack up and manufacturing defects, plus some consumer rough housing. This minimizes warranty claims and as well as accommodate for different environments (i.e. Higher or lower altitude). Also, a higher HP gain does increase the stress that the cylinders see but the killer would be if you can't keep the engine at the correct operating temp or if you over rev it.

If you put too much dome pressure from an oversized turbo with no blow off valve, most likely you'll blow a head gasket and break your head bolts but you probably won't grenade your motor. If you have a cooling system that can remove 400 Watts but you have it hooked up to one that makes 450 watts the thing will weld itself together.
Diesels do not use blow off valves there is no throttle body like a gasoline engine. Typically on a gas engine when decelerating the blow off valve diverts excess boost away from the throttle body while closing. The wastegate on a diesel is used to control boost. I am running the factory setting on the tdo3 turbo which is 8 psi. Most guys swapping these motors are pushing 20-25psi. Saying they are overbuilt is an understatement. You simply will not kill this engine at 40-50hp. Now if your running 100+Hp swapped into a Jeep you’ll need to monitor exhaust gas temps climbing hills. The stock Kubota cooling system with my setup has plenty of capacity for the power I am running. The turbo doesn’t really generate that much more heat. It does however increase efficiency.



For instance I’ve been building diesel powered drag engines for the past 8 years. Take a Cummins 4bt in its stock form hp is 120. torque is 265ftlbs. Stock max rpm 2500.


I have pushed the engine in my chevy drag truck to 600whp and 935 ftlbs torque at 4800rpms. A solid 400% increase in power. Diesel engines can handle the abuse it’s all in the proper fueling and keeping The turbo in its efficiency range.
 

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Mikemoto17

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L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
9
19
3
California
Interesting spec comparison.

I wonder if it is the same engine, with the specs rounded to make it look slightly different due to the break point for emissions being so close to the L2501's HP rating? Having read the L2501 engine is de-tuned, I have wondered what tractor uses the same engine in a higher HP version.

I understand from reading here at OTT that the L2501 shares the same mechanical drive line as the two bigger brothers, the L33xx and L39xx. So from that perspective your increased HP should not be a great concern.
Hey so to answer your question after researching both engines Kubota simply pulled the timing down to 5 degrees btdc. They also lowered the max fueling of the injection pump to meet tier4 requirements. Simply bumping the timing up on the d1703 and adding fuel will get you slightly over 30hp which is what this engine was originally rated to run at. Now for me that still wasn’t enough power. I decided on the turbo to bring it up around the low 40hp mark. Now I can do way more with this tractor than I thought I ever could and don’t have any emissions crap to deal with lol 😂
 
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Joel K

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L2501
Nov 22, 2018
22
0
1
Bay City MI
Hey so to answer your question after researching both engines Kubota simply pulled the timing down to 5 degrees btdc. They also lowered the max fueling of the injection pump to meet tier4 requirements. Simply bumping the timing up on the d1703 and adding fuel will get you slightly over 30hp which is what this engine was originally rated to run at. Now for me that still wasn’t enough power. I decided on the turbo to bring it up around the low 40hp mark. Now I can do way more with this tractor than I thought I ever could and don’t have any emissions crap to deal with lol 😂
Hi Mike,

Can you explain how to change the timing and increase fuel flow? I did the rpm increase last year and bumped up the Hydraulic pressure a good 400 psi with not problems. However i could use a little more power with all of the ground engaging work I do with my tractor. Thanks. And if you prefer you can pm me.
 

tractorX

New member

Equipment
KUBOTA L2501 DT 4WD 525 FEL SSQA, 5' BOX BLADE, 42" FORKS
Sep 27, 2013
5
1
3
Rock Spring GA.
Hey so to answer your question after researching both engines Kubota simply pulled the timing down to 5 degrees btdc. They also lowered the max fueling of the injection pump to meet tier4 requirements. Simply bumping the timing up on the d1703 and adding fuel will get you slightly over 30hp which is what this engine was originally rated to run at. Now for me that still wasn’t enough power. I decided on the turbo to bring it up around the low 40hp mark. Now I can do way more with this tractor than I thought I ever could and don’t have any emissions crap to deal with lol 😂
mike, can you make a youtube vid or post a detailed sketch for the timing and fuel procedure... be most appreciated!

btw, the ole chevy truck is bad @ss too... dude your work speaks for itself!
 

g9vi6185

New member

Equipment
L3901
Nov 23, 2020
6
0
1
Northern MI
I have a L3901 and have been trying to figure out how to check my hydraulic pressure. I have a LP 3rd function set up for a Grapple as well.
So I made a gauge with a 5000 psi liquid filled gauge attached to a Kubota female QD coupler. I have seen a few pics where guys attach the gauge to the "blue cap" (top right connecter of the four) loader male connects on the valve assembly by the loader handle. I get nothing on the gauge? I tried all the connections and still get nothing?
Do I have a bad gauge? Do I need a male fitting and put the gauge on the loader line instead of the valve assembly (saying it wrong?). Do I need a 3/4 pioneer coupler and hook to my 3rd function to test?
I see the disconnect line move, tighten up when I bump the right loader control.

Thanks
 

ccoon520

Member

Equipment
L2501 w/ FEL
Apr 15, 2019
152
10
18
IA
Diesels do not use blow off valves there is no throttle body like a gasoline engine. Typically on a gas engine when decelerating the blow off valve diverts excess boost away from the throttle body while closing. The wastegate on a diesel is used to control boost. I am running the factory setting on the tdo3 turbo which is 8 psi. Most guys swapping these motors are pushing 20-25psi. Saying they are overbuilt is an understatement. You simply will not kill this engine at 40-50hp. Now if your running 100+Hp swapped into a Jeep you’ll need to monitor exhaust gas temps climbing hills. The stock Kubota cooling system with my setup has plenty of capacity for the power I am running. The turbo doesn’t really generate that much more heat. It does however increase efficiency.



For instance I’ve been building diesel powered drag engines for the past 8 years. Take a Cummins 4bt in its stock form hp is 120. torque is 265ftlbs. Stock max rpm 2500.


I have pushed the engine in my chevy drag truck to 600whp and 935 ftlbs torque at 4800rpms. A solid 400% increase in power. Diesel engines can handle the abuse it’s all in the proper fueling and keeping The turbo in its efficiency range.
I was unaware of the waste gate vs blow off valve thanks for bringing me up to speed. Also please don't take my comment on the cooling as thinking the current system didn't have the headroom for it the added HP. If my phrasing suggested that I apologize I was just trying to point out that heat is a bigger threat than 10 psi of boost and the extra fuel in general not specifically with this setup. I had no doubt in that especially since it is probably the same as the one in the L3901 to keep their costs down and for simplicities sake.

Turbos are an amazing thing because they use otherwise lost energy to increase power output and are especially good on things like tractors. Turbo lag isn't an issue when you are constantly at operating speed/load so you don't need to worry about building boost. Which is why I prefer them to superchargers (in general) because I don't have to worry about parasitic losses from trying to spool up the turbine with the crank. Now if that pesky warranty and loan can run out so I can look into getting a little extra oomf out of my 2501.
 

KBW

New member

Equipment
L2501, LA525 Loader, BB1260 Box Blade
Nov 26, 2020
1
0
1
Arizona
Great thread Mike! Like many above, I want to do this when my new L2501 goes out of warranty, and if you make the kit I will likely buy and put on the shelf until it can be bolted on. I figured the engine was detuned, and had a lot of potential, but you have found more than I expected. A dyno run would be very interesting! You may have created a monster......