L2501 Modifications

Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
Hey Guys new to this forum. I own a performance shop and I build turbo kits. I started in the diesel world with a 4bt swapped 47 Chevy currently making 600whp 950 tq on 70 psi. I also build custom turbo kits for bmw platforms. I purchased 5 acres of property and jumped on buying an l2501 HST. Reason being is I knew this engine was de tuned from all my research and not having a dpf was a big plus. I am also a huge fan of mechanically controlled Diesel engines. I started off doing a basic rpm increase to 2600rpms. It helped with running my PTO chipper but I eventually found out I needed more fuel. I made a very slight fuel adjustment and it did increase the power. Only issue was of course slightly more smoke. After reading about the D1703 I figured out Kubota retarded the timing to 5 degrees btdc for emissions and to help it get under 25hp and also the air box they are using is a major restriction. The 1703 can run up to 14 degrees btdc. I bumped the timing up to 9 btdc and installed a higher flowing air box and all I can say is wow this thing pulls up my driveway which is a 15% grade like no problem in mid range gear at 2300rpms. Before it would bog down below 1800. I am guessing it’s in the mid 30hp range. Just wanted to share this info. And I will be also installing an oem rhf3 Kubota turbocharger. I’ll be running low boost probably around 5-7 psi. Since I am at 3,000 feet elevation it will help a ton. I’ll post pictures and progress hoping for a solid 40hp out of this tractor 😎😂
 
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85Hokie

Well-known member
Lifetime Member

Equipment
BX-25D w/ Filled Rears,2" Spacers,PTB. Under Armor, 90'-90'-92'-B7100HST's
Jul 13, 2013
8,121
463
83
Bedford - VA
Can't wait to see some pictures of that engine. Anyway to dyno this beast?
 
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Tornado

Active member
May 7, 2019
697
166
43
usa
Hey Guys new to this forum. I own a performance shop and I build turbo kits. I started in the diesel world with a 4bt swapped 47 Chevy currently making 600whp 950 tq on 70 psi. I also build custom turbo kits for bmw platforms. I purchased 5 acres of property and jumped on buying an l2501 HST. Reason being is I knew this engine was de tuned from all my research and not having a dpf was a big plus. I am also a huge fan of mechanically controlled Diesel engines. I started off doing a basic rpm increase to 2600rpms. It helped with running my PTO chipper but I eventually found out I needed more fuel. I made a very slight fuel adjustment and it did increase the power. Only issue was of course slightly more smoke. After reading about the D1703 I figured out Kubota retarded the timing to 5 degrees btdc for emissions and to help it get under 25hp and also the air box they are using is a major restriction. The 1703 can run up to 14 degrees btdc. I bumped the timing up to 9 btdc and installed a higher flowing air box and all I can say is wow this thing pulls up my driveway which is a 15% grade like no problem in mid range gear at 2300rpms. Before it would bog down below 1800. I am guessing it’s in the mid 30hp range. Just wanted to share this info. And I will be also installing an oem rhf3 Kubota turbocharger. I’ll be running low boost probably around 5-7 psi. Since I am at 3,000 feet elevation it will help a ton. I’ll post pictures and progress hoping for a solid 40hp out of this tractor 😎😂
Very cool Mikemoto. I have the same tractor. I spend my time tweaking and overclocking computer components rather than engines. I'm curious if you know of any simple tweaks a general L2501 owner could do to increase performance of the tractor just a smidge? I notice you metnion the airbox being restrictive - You know they make an inner air filter that fits in that airbox (The filter is not included with the L2501 as standard) Many of us add this additional inner air filter just as additional security in dusty conditions, or working around lots of smoke / ash from brush firing. It has come up when discussing the adding of that additional filter "Does it restrict airflow, and thus hurt performance?" In my case, I have not noticed any change at all from running the added filter, but I'm curious what your thoughts would be on that given your knowledge. Having tweaked the engine and spent some time getting to know it, I'm also curious about any potential simple tweaks you may know of that could possibly allow a little extra from the engine. Like you, I have read that the same engine in the L2501 is actually the same engine Kubota uses in other tractors in other countries and sells them at around 30HP, so Its long been known that the engine is detuned a little. Any easy ways to squeeze some of that back out?

Welcome to the forums :)
 
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Roadworthy

Active member
Lifetime Member

Equipment
L2501 HST
Aug 17, 2019
890
113
43
Benton City, WA
I don't know if I'll ever get around to playing with a horsepower boost as my L2501 does its job just fine as is. I do appreciate you taking the time to post the results of your tinkering. Thank you for sharing what you've learned.
 
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Tornado

Active member
May 7, 2019
697
166
43
usa
To follow up more on my post above... I ask about simple tweaks because I have seen folks who have made a simple 5 minute adjustment to the RPM limiter screw that allows you to push the L2501's RPM above its stock maximum. This is a very simple modification to make, but I've never done it because, not being a mechanic, I'm not sure of any other possible ramifications of doing so. I have seem for example that you can take the engine to around 30hp by simply increasing the max RPM a little, allowing the engine to go up to around 3,000rpm. One little screw will allow this to happen, but is it wise to do this, does it have any negative impact on the engine, etc. I dont have an intimate enough knowledge of the engine to know how that would work out.
 

Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
To follow up more on my post above... I ask about simple tweaks because I have seen folks who have made a simple 5 minute adjustment to the RPM limiter screw that allows you to push the L2501's RPM above its stock maximum. This is a very simple modification to make, but I've never done it because, not being a mechanic, I'm not sure of any other possible ramifications of doing so. I have seem for example that you can take the engine to around 30hp by simply increasing the max RPM a little, allowing the engine to go up to around 3,000rpm. One little screw will allow this to happen, but is it wise to do this, does it have any negative impact on the engine, etc. I dont have an intimate enough knowledge of the engine to know how that would work out.
Hey! Yes an rpm adjustment will make more hp but you will loose tq drastically especially above 2500. The only way to raise the peak torque in the power band is to add timing. Let’s say the engine in its stock form makes peak torque at 5 degrees of timing at 1650rpms which I believe is around 75ftlbs. Increasing the timing to 7-10 degrees will bring peak torque up in the power band to around 1800-2,000rpms only then does it make sense to increase your rpms to 3,000. I would recommend doing a slight increase to 2600. It helped me a lot when I first got my tractor. It’s only a 200rpm increase and helps the engine carry a load better and not drop rpms as fast.
 
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Tornado

Active member
May 7, 2019
697
166
43
usa
Hey! Yes an rpm adjustment will make more hp but you will loose tq drastically especially above 2500. The only way to raise the peak torque in the power band is to add timing. Let’s say the engine in its stock form makes peak torque at 5 degrees of timing at 1650rpms which I believe is around 75ftlbs. Increasing the timing to 7-10 degrees will bring peak torque up in the power band to around 1800-2,000rpms only then does it make sense to increase your rpms to 3,000. I would recommend doing a slight increase to 2600. It helped me a lot when I first got my tractor. It’s only a 200rpm increase and helps the engine carry a load better and not drop rpms as fast.
Great info Mike thanks. I knew there would be a lot more "strings" attached to this. Its not entirely unlike overclocking computers. Pushing one variable up causes a whole series of things to happen, and creates demands in other areas. Without an intimate knowledge of how this all works in conjunction with one another, you cant really understand how all the dots connect and how moving one affects the others. I may try bumping my RPM a little to see how it goes. I understand you have to void the warranty to do this though. Ill think about it :D
 

bx tractorjoe

Active member

Equipment
kubota l2501 upgraded from a bx23s john deere 670 husquarvana huv 4421 gxp
Jun 3, 2020
256
119
43
loxahatchee flordia
The only downside to adjusting the injection pump and timing is the possibility of it building up carbon on the piston and over time causing a hot spot, im not saying it will by turning the fuel up a little, but have seen it happen mostly when kids crank up the fuel and adding bigger injectors on a 12v Cummins and treat it like a hot rod and burn a hole in the piston.

Once my warranty is over on my l2501 id advance the timing and turn up the fuel on it as well.. roll some coal!
 

NetMagi

Member

Equipment
BX25D (sold), L2501HST w/BH77 Backhoe
Dec 30, 2014
99
23
8
Pennsylvania
Hey Guys new to this forum. I own a performance shop and I build turbo kits. I started in the diesel world with a 4bt swapped 47 Chevy currently making 600whp 950 tq on 70 psi. I also build custom turbo kits for bmw platforms. I purchased 5 acres of property and jumped on buying an l2501 HST. Reason being is I knew this engine was de tuned from all my research and not having a dpf was a big plus. I am also a huge fan of mechanically controlled Diesel engines. I started off doing a basic rpm increase to 2600rpms. It helped with running my PTO chipper but I eventually found out I needed more fuel. I made a very slight fuel adjustment and it did increase the power. Only issue was of course slightly more smoke. After reading about the D1703 I figured out Kubota retarded the timing to 5 degrees btdc for emissions and to help it get under 25hp and also the air box they are using is a major restriction. The 1703 can run up to 14 degrees btdc. I bumped the timing up to 9 btdc and installed a higher flowing air box and all I can say is wow this thing pulls up my driveway which is a 15% grade like no problem in mid range gear at 2300rpms. Before it would bog down below 1800. I am guessing it’s in the mid 30hp range. Just wanted to share this info. And I will be also installing an oem rhf3 Kubota turbocharger. I’ll be running low boost probably around 5-7 psi. Since I am at 3,000 feet elevation it will help a ton. I’ll post pictures and progress hoping for a solid 40hp out of this tractor 😎😂
Please keep us updated. I also recently acquired an l2501, and would love to see another 5ish hp out of it. Would you consider doing a step by step guide once you’re satisfied the mods are solid?

I love the torque this thing makes at low rpm’s, but it seems to smoke a fair bit unless i bring the revs up anyway.
 

Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
Please keep us updated. I also recently acquired an l2501, and would love to see another 5ish hp out of it. Would you consider doing a step by step guide once you’re satisfied the mods are solid?

I love the torque this thing makes at low rpm’s, but it seems to smoke a fair bit unless i bring the revs up anyway.
No problem I will make a guide on the changes I made and the power expected.

Also major update!!!!!
I just finished installed a MHI tdo3 7G turbo. This is the same setup on the v2003t Kubota engine. It spools beautifully and this tractor is making at least double the hp. It literally flies up my hill in H gear. The sound is absolutely amazing and this turbo cleans up very nice no smoke the tractor runs super clean under a load. if you anyone is interested let me know. I’ll ship you a kit 😎🤘 here are some teaser photos. The exhaust is not done and the adapters I made still need some trimming and I will be ceramic coating all 304ss hot parts. Check it out!!
 

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Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
No problem I will make a guide on the changes I made and the power expected.

Also major update!!!!!
I just finished installed a MHI tdo3 7G turbo. This is the same setup on the v2003t Kubota engine. It spools beautifully and this tractor is making at least double the hp. It literally flies up my hill in H gear. The sound is absolutely amazing and this turbo cleans up very nice no smoke the tractor runs super clean under a load. if you anyone is interested let me know. I’ll ship you a kit 😎🤘 here are some teaser photos. The exhaust is not done and the adapters I made still need some trimming and I will be ceramic coating all 304ss hot parts. Check it out!!
link to a sound clip!!!
http://instagr.am/p/CHRlarFnyCm/
 
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XrTweaked

New member

Equipment
L2501DT
Sep 23, 2020
4
1
3
Cincinnati
Very nice Mikemoto17!!! I just recently bought a new L2501DT and once the warranty is near the end, I'll be considering this as well. The tractor has plenty of torque for everything I'm putting it through, but I can never leave things the way they are and am always looking to maximize them. :)
 

drewzee87t

Active member

Equipment
B2910 HST, Modern RC, Gannon Earthcavator, Frontier 1150 Tiller, Woods RM306
May 20, 2016
114
31
28
misery
The adaptor between the turbine inlet and the exhaust manifold. I am looking to turbo a v1505 engine and I can swap out to a turbo manifold but then I can only bolt on TD025 (Oh too small) with triangle pattern. Looking to put a TD03 on it but I haven't seen a good way to adapt to the NA exhaust without having the turbo sticking up or out a couple extra inches for the adaptor.

I think the exhaust flange are the same on all the na manifolds like square 2.5" whatever that is metric. Looks like you just made a plate like one would use to convert a T4 turbine to a T3 exhaust. I need that.

The downpipe would be a great part too from the turbine outlet flange with the conical expansion pipe. Where you welded on your j bend to curve down maybe put a v-band flange? Then anyone could just have a shop fabricate from the v-band to wherever the exhaust wants to go.

Very cool. I was looking at youtube's on some crazy indonesian's or maybe fillipinos that have all turbo'd their kubotas and the things are awesome. There is also the kubota swappers doing turbo kubota's into old jeeps and stuff, so maybe some aftermarket there. They all seem to be working with V2203 base.
 

greenacresnorth

Member

Equipment
L2501,BH77
Feb 18, 2018
175
23
18
35
Morganton,NC
@Mikemoto17, make sure you re route your CCV, I ran mine to a small catch mounted up forward of the rad, never get any oil or smell. also you may want to wrap your turbine housing, the paint on the hood doesn't play with heat to well.
 

Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
The adaptor between the turbine inlet and the exhaust manifold. I am looking to turbo a v1505 engine and I can swap out to a turbo manifold but then I can only bolt on TD025 (Oh too small) with triangle pattern. Looking to put a TD03 on it but I haven't seen a good way to adapt to the NA exhaust without having the turbo sticking up or out a couple extra inches for the adaptor.

I think the exhaust flange are the same on all the na manifolds like square 2.5" whatever that is metric. Looks like you just made a plate like one would use to convert a T4 turbine to a T3 exhaust. I need that.

The downpipe would be a great part too from the turbine outlet flange with the conical expansion pipe. Where you welded on your j bend to curve down maybe put a v-band flange? Then anyone could just have a shop fabricate from the v-band to wherever the exhaust wants to go.

Very cool. I was looking at youtube's on some crazy indonesian's or maybe fillipinos that have all turbo'd their kubotas and the things are awesome. There is also the kubota swappers doing turbo kubota's into old jeeps and stuff, so maybe some aftermarket there. They all seem to be working with V2203 base.
Hey man! Attached below are the kits I normally build. It’s mainly a hobby/passion that turned into a business for me but I enjoy fabrication. I currently produce turbo kits for the bmw n54 335i and s55 M platforms check out our website 4NMotorsport.com. This kit on my tractor was pieced together with material I had laying around the shop just for testing. I will absolutely add a 2.5 v band flange and if I decide to sell some I’ll have a full 304ss exhaust included with everything. If you want me to make you a flange for your v1505 to tdo3 turbine housing adapter I can absolutely do that!
 

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Mikemoto17

Member

Equipment
L2501 HST BH77 backhoe LA525 loader woodland Mills Pto chipper
Oct 21, 2020
10
35
13
California
@Mikemoto17, make sure you re route your pcv, I ran mine to a small catch mounted up forward of the rad, never get any oil or smell. also you may want to wrap your turbine housing, the paint on the hood doesn't play with heat to well.
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 😂