Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results

   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #91  
Part 1: Background

The purpose of this thread is to share the concept, creation, progress and performance of my custom Turbocharged Kubota L2501 HST 4WD tractor.

I’ll start by offering my opinions on this tractor, why I bought it, how it’s performed, the advantages and disadvantages, and why I chose to modify it in such spectacular fashion.

This thread is not intended to compare alternative tractors (smaller, larger, heavier models, different brands, etc.). That said, I will be making some statistical comparisons between Kubota’s Standard L Series tractors, since, they are all, basically the same tractor with varying cost and performance aspects.

Let’s begin.

My Kubota L2501 HST 4WD is my second tractor (third, if you include the garden-tractor variety).

I’m operating my tractor on 5 acres of undeveloped heavily wooded forest land. The property itself is roughly 500ft above sea level and the terrain consists of flat areas along with moderate and steep hills to the north and northeast.

My goal with the property is to transform the wild untamed forest and create a park-like atmosphere and appearance without disturbing too much of the natural beauty.

My tractor is used to grade and level land, till dirt, move dirt, move brush, skid logs, transport trees and logs, make trails through the forest, maintain our gravel driveway, remove stumps, run a PTO powered wood chipper, run a 15KW PTO backup generator and to load and unload miscellaneous materials and products from delivery trucks.
Thankfully, I have a ZTR mower (zero-turn riding lawnmower) to maintain the grass, weeds and light brush.

When I first began shopping for a tractor I focused my attention on the sub-compact variety. I wanted a small, all-in-one machine, that could fit anywhere, feel comfortable, do tractor things, but also, mow the lawn.

Mowing the lawn was a very important consideration at this particular time in my property ownership career. I was fixated on acquiring a versatile tractor capable of mowing the grass since I had grown tired of having to stop in the middle of my mowing chores to fill the gas tank on my garden tractor. A truly loathsome inconvenience! I wanted to make certain that whatever tractor I purchased would have enough fuel capacity to mow my entire property on one tank of fuel and I knew a small diesel powered tractor wouldn’t have any issue accomplishing this task. That said, I was also beginning to realize the need for a real tractor to help with property management, improvements and maintenance tasks. At this early stage in my understanding, I didn’t have a bona fide vision, or grasp of a tractors true capabilities.

Friends, neighbors and co-workers familiar with my property quickly lured me away from purchasing a small sub-compact tractor and suggested I go bigger, much bigger. Most folks were urging me to buy a medium to large compact or, even a small utility tractor. But, doing so, meant having to purchase two separate machines. One for tractor work and one for mowing duties. The thought of purchasing two machines seemed completely unnecessary and incredibly expensive. Further complicating my decision making ability was due to my ignorance and inexperience. At the time, I didn’t fully understand the limitations of a tractor’s size and weight. Consequently, I was unable to fully comprehend the reasoning behind each of the tractor recommendations that were being offered to me. Purchasing a small tractor, with a mid-mounted mower, seemed to make a lot more sense. Respectfully, however, I couldn’t entirely disregard their suggestions since I knew they were all based on decades of operating experience from very knowledgeable individuals that really wanted to help me buy the ideal tractor for my property.

After cross-shopping many brands, tractors and tractor sizes, I eventually made a decision. A decision that pretty much disregarded all the advice and suggestions I received. A decision purely based on my own enormously extensive inexperience. My decision was to purchase a brand new Kubota B2601 HST 4WD tractor equipped with a front end loader and of course, most importantly, a 60” MMM (mid-mount mower). In the end, I just didn’t think a larger tractor was necessary. I’m just mowing the lawn for heavens sake!

I was tremendously proud of my decision because I technically bought a larger tractor than I was originally planning to purchase. I bought a compact tractor, not a sub-compact tractor! In my mind, this slight increase in tractor size was surely enough to appease the generous souls that offered me their advice and wisdom. See I listened! Hooray for me!
Though, in reality, I didn’t listen. The B2601 was nowhere near as big, or as heavy as the tractor I was originally encouraged to purchase.

View attachment 786026

As disappointed as some individuals were regarding my decision, they were still happy I purchased a tractor. Because any tractor, is better than no tractor! And honestly, purchasing the B2601 wasn’t a horrible decision after all. It was a great tractor and served me well, but it just wasn’t the ‘right’ tractor for my property and uses. The B2601 simply lacked the lift capacity, the size and the weight required for removing medium to large stumps, carrying logs, carrying stumps and the heavy ground engagement work that was still needed on my property.

I’m sure most of us can agree, first hand experience is paramount. Nothing teaches you more than learning from your own mistakes. It can be painful but, I welcome it. That said, I always hope my mistakes aren’t too costly fiscally or physically. Luckily, this one wasn’t and within a year, I was once again visiting local tractor dealerships prepared to purchase a larger tractor (and a dedicated lawn mower).

When you are in the market for a new tractor, it’s worth repeating some very wise tractor shopping lore;
Tractors in general, appear gigantic at the dealership parked side by side one another, and then, when you get them home, they mysteriously shrink! Have you noticed this? It’s hilarious, but true!

After many agonizing (enjoyable) weeks of research, visiting dealerships and cross-shopping multiple brands and tractors such as the John Deere 3025E, Massy Ferguson 1825E (and 1835M), Kioti CK2610H, LS MT225HE, Branson 2515H and several others, I was drawn to and eventually purchased the Kubota Standard L Series L2501 ‘Economy’ tractor.

View attachment 786027

I purchased the Kubota L2501 for several reasons. First and foremost, bang-for-your-buck. You get a lot of pure tractor for the money. The L2501 is a substantial, raw and robustly designed machine made for arduous tractor work. The combination of its size, weight, lift capacity, and maneuverability are near perfect for my property. The L2501 has an impressive track record for trouble free operation, exceptional build quality and amazing reliability. In addition, the L2501’s three cylinder diesel engine delivers exceptional fuel economy and also produces an impressive amount of torque for its size, especially considering it is a naturally aspirated. Having owned several overly complicated and expensive modern diesel powered cars, trucks and SUV’s, I appreciate simplicity. The L2501’s engine is thankfully, a simple mechanical diesel and is not equipped with modern diesel emissions equipment, or electronics. Meaning it does not have an ECM (engine control module) or DPF (diesel particulate filter) and doesn’t require emission Regens (a process that converts soot to ash within the exhaust system) which create excessive heat, wastes fuel and mandates high RPM engine operation. A huge bonus for sure! Furthermore, another benefit is the L2501’s popularity. It’s one of the best selling tractors in the USA and has very good resale value (an important consideration when you’re not fully confident in your purchasing decisions, like me).

All of these characteristics seemed extremely well suited for my property and my intended uses. Plus, I was already familiar with the Kubota brand, I have a phenomenal dealer less than 40 miles away and the L2501 was the tractor that many folks, including my Kubota dealer, originally recommended.
Whew! That’s a TON of good stuff! Sold!

View attachment 786028

The L2501 is an awesome tractor but, is it the perfect tractor? Not quite. So why isn’t the L2501 a perfect tractor?
Several things, let me explain.

Naturally, I’ve spent quite a bit of time reading, researching and operating the Kubota L2501 tractor. During this process I’ve catalogued many of the complaints expressed from owners, previous owners, shoppers, hater’s and those in between.

Here’s a synopsis of those opinions I’ve compiled over time.

The L2501 is a budget minded economy tractor that lacks creature comforts and doesn’t offer exceptional ergonomics and controls, especially when compared to its rivals. Absolutely correct! But, the L2501’s hydraulic operation is twice as smooth as the competitors and seriously, this is a budget tractor. These limitations are pretty much expected from a tractor in this category, Right?

Cost. The Kubota L2501 is expensive when compared to other 25HP economy tractors. It ain’t worth the money dummy! There’s some truth to this. In most cases, the L2501 will cost more than an alternative brand economy tractor. Admittedly, you’re buying the brand, Kubota. But, you’re also buying a strong dealer network. You’re buying quality, exceptional engineering, design, reliability, long term parts availability and high resale value.
Hmmm, come to think about it, there might be some additional value there. You make the call.

The L2501’s most obvious disadvantage and unquestionably the most meaningful, is the low engine horsepower and measly PTO power output which affects the tractor’s ability to get work done.

What is the PTO? The PTO (power take off) is the tractors stub shaft that transfers power to a PTO driven implement, or machine. Power transfer is accomplished by connecting a drive shaft from the implement to the tractors PTO stub shaft. Got it? Great.

The low PTO power drastically limits the size, type and availability of rear PTO powered implements you can effectively run with the L2501.

The low engine power effects operating speed and slows the tractor down while powering and running rear PTO implements, like a flail mower, tiller, snowblower or large rotary cutter. This issue can be compounded depending on conditions such as tall grass and/or steep terrain. Conditions like these may require using Low gear, slowing down the operating speed and/or potentially stalling the tractor.

The same can be said for larger heavier dirt working ground-engagement implements too, like box blades and land planes. The L2501 can lift and carry them without issue but, the larger implements, full of material can create too much drag and the tractor simply doesn’t have enough power to pull these type of implements at optimal speeds. Once again, conditions such as these would very likely require using Low gear, slowing down the operating speed and/or potentially stalling the tractor. Steep hills, or challenging terrain can make these tasks impossible.

Even though the L2501 has three forward gears, in reality, it only has two fully usable gears, Low and Medium gear. The High gear? Not so much. The L2501 gear situation has been explained to me as; (L) for loader work, (M) for mowing and (H) for highway. While this interpretation makes perfect sense, the (H) gear is virtually useless on this tractor. Basically, the (H) gear can only be used for transportation purposes, on completely flat terrain. Hills? Forget about it.

And, the L2501’s engine, being naturally aspirated and having only 24.8 HP can cause performance to suffer in high altitude operation (luckily, something I don’t have to worry about).

While the L2501 might not be perfect, it has performed near flawlessly on my property and has done everything I’ve asked of it. Perhaps, my annoyance with this tractor is because I want work to get done faster and I believe it is possible to improve the L2501’s overall performance. Am I impatient? Yep! The question is; can I make the L2501 the perfect tractor?

In order to do that, I must explain the key challenges I experience on my property with this tractor.

For example, I transport all of my brush, trees, logs, stumps and basically anything I need to burn up and over a long steep hill. This hill is a 22* slope, 40% grade. It’s fairly steep and 4WD is required in almost anything that goes up, or down the hill. My L2501 can make it up the hill, carrying a load in both (L) and (M) gears at a minimum of 2,200 RPM. In (L) gear, going up the hill is excruciating slow and frustrating. In (M) gear, the tractor struggles and bogs down several hundred RPM’s as it climbs the hill, slowing to a crawl and requires feathering of the HST pedal to maintain progress. (M) gear is certainly better than (L) gear but, (M) gear is still really slow and it’s difficult to maintain a consistent speed. In (H) gear? Uhhh, no. The tractor bogs down and stalls, regardless of engine RPM. I don’t necessarily need the tractor to get up the hill faster but, I’d like to have more power to maintain speed while going up this hill, in (M) gear. In the tractor’s present state, I think it would be impossible, for example , to power a large rotary cutter, or even pull a box blade going up this hill, in anything but (L) gear.

Also, the L2501 doesn’t seem to have enough power to pull a heavy commercial box blade full of material in (M) gear. I would like to have more power to use the larger, heavier ground engaging dirt working implements in challenging conditions at my desired operating speeds.

Speaking of operating speeds. I’d like to be able to have full use of (H) gear and maintain ground speed regardless of the terrain conditions. Hills and flat terrain. Remember? I’m impatient!
Right now, I can’t fully utilize (H) gear, even for transportation purposes and that needs to change.

I’d also appreciate having more power for my PTO powered wood chipper and have enough power to run a 15KW PTO backup generator.

Okay. I know what you’re thinking, Mike you moron! Kubota already has a solution to the shortcomings of your weak, overrated, underperforming and worthless L2501 tractor. Your prayers are answered!!! The L3901 HST 4WD!!! Heck, you fool! You may be able to save a little money and get away with a L3301 HST 4WD!!! Now, sell your embarrassing L2501 immediately and get a real tractor!!! One with power to spare!!! You’re welcome….You jackass!!!

Perhaps you’re right. But, not so fast. I bought the L2501 for it’s simplicity. It’s reliability. It’s value. I bought the L2501 because I don’t want to deal with computers, emissions, Regens, DPF, or high rpm operation. These are things that become a nuisance, a hinderance, a concern with ownership over time. I don’t want the added complexity, complications, or the additional cost.

Hmmm, what are my options then?
Let’s take a look.

Mike
From reading you situation you need to pull up New Holland Workmaster 50 tractor info and specifications and buy something that compares. Weight, loader lift capacity and horse power.
I needed about 30 hp tractor in 2013. Took 3 years of comparison and saving my money to convince myself a 50 hp was what I needed to satisfy my wants and needs. March of 2016 purchased a new Workmaster 50 4x4. Since then I have purchased forks, stump bucket, log skider, scrape blade, bucket cage and already owned an 8 ft box blade.
Setting on dealer lot it looked way to big for me. When I got it home and hooked the 8 ft box blade up it looked about right size. Since 2016 the tractor and loader have increased about $10,000 dollars. I can sell now for more than what I paid for it. Kind of makes you feel good each time you are using it but in your mind the only way another person is going to enjoy that experience is to purchase one from someone else because money can't buy yours.
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #92  
Thank you.

The L2501, L3301, L3302, L3901 and L3902 all share the same Hydrostat unit and the same 28:27 input ratio. All components in PTO are the same with the exception of two gears. You can match PTO speeds in the L2501 by replacing those two gears.

The L2501 HST relief pressure is only 100psi lower than the L3301 / L3302 and L3901 / L3902.

Mike
I have a L 2500 for a few years ....same as the others
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #93  
What about oil cooled pistons? I have been in the truck and tractor repair business that I own for over 50 years. I read the write up pretty fast because it was easy for me and often knew what was going to be said before I read it.
Glad you like it. I also owned a grading business and retired from that just as they were forcing the tiers upon that company.
When it comes to earth work it’s all about weight and torque. One always limits what the other can do.
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results
  • Thread Starter
#94  
You should perform a leakdown test on your machine at some point as the turbo install will erode the piston ring land on the top ring only and compression will suffer especially if you use much power over sustained time. These folks will help you also.

I have another 400 on it blowing snow wide open full tilt and have yet to have another issue but haven't done another leakdown test yet, again, perform a leakdown test not a compression test.
I stopped posting here much to the chagrin of the hall monitors here, only Elon Musk knows what I am speaking of; and yes I do still hate my tractor.

Great suggestion. It all depends on application and setup. Did you ever monitor your EGT temperatures? Sounds like you may have had excessive run away EGT’s during hard operation. That’ll kill any engine.

Anybody installing this Turbo kit will need to monitor EGT’s. The end user is responsible for tuning. You can combat high EGT in two ways; reduce fuel or add more boost PSI (adjust boost actuator on Turbo). Both can be accomplished on this setup.

Mike
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #95  
I turbocharged my L3940 and it ruined all 4 pistons in 400 hours. Pull the part numbers of your pistons and compare with the actual turbocharged version, you'll see what I am talking about.

I have a thread here somewhere called "I still hate my tractor", it's about too many pages long, about my turbo install and experiences with it.
I stopped posting here much to the chagrin of the hall monitors here, only Elon Musk knows what I am speaking of; and yes I do still hate my tractor.
The Fred returns! We Miss your wit and tractor updates, dude.

Yes, a piston is very much designed specifically for the conditions expected (cylinder pressure, temperature, power level, etc).
If you’re lucky, Kubota or whoever is lazy and used the same strong piston in a derated n/a engine version. However this uncommon and unexpected, because pistons with more structure and features to withstand high loading in a turbocharged engine are more expensive for the supplier to manufacture, and thus also for the OEM to buy.

If you’re even more lucky, the more basic n/a motor piston can still survive with 50% more power, pressure and higher temperatures. But i sure wouldn’t count on it working this way under sustained full load for hundreds of hours.
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #96  
An a pyrometer / EGT should be mandatory for someone modifying their diesel as aluminum melts at above 1100 degrees F.

Turbo pistons are often hard anodized to resist heat and sometimes have a steel insert for the top ring.

That said M&W made turbo kits for farm tractors in the sixties and seventies. They were used on tractors like JD 4020 and IH 966 to name two.

I was told by a IH shop foreman that you need to turn the fuel on the pump up to avoid running lean IIRC.
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #97  
Very well done on your entire journey. Nice to know about the dyno on the west side. My neighbor bought this same tractor from me and would like a bit more power for our steep canyon. I would end up being the installer if he decides to go with the turbo mod. Thanks for sharing your time and knowledge. GO GEARHEADS!
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #98  
Turbo pistons are often hard anodized to resist heat and sometimes have a steel insert for the top ring.
EXACTLY, and every OEM turbocharged, boosted car sold today has this insert installed for the top ring land.

You'll notice 3 basic differences on Kubota NA vs. boosted pre tier 4 engines.

1) intake manifold, NA has a runner type or non plenum manifold, the boosted always have a "log" type manifold or one with a plenum, simply a large area that evenly distributes the pressure to each runner. So where a naturally aspirated engine has a vacuum at each intake valve a boosted engine has pressure at each intake valve, at load that is. I learned this from a Dodge Cummins truck pull champion, he showed me how the Cummins manifold needs a plenum because the rear cylinders get much more charge without it and they are usually the first ones to fail.

2) Oil cooler, there are no piston oil squirters on the pre-emission Kubota engines, not sure about the newest ones, please correct me if I am wrong.

3) Pistons with that hard insert on the top ring, to help with the major increase in combustion pressure.
As far as I could tell that is about it, they usually run the same timing spec and fuel injector although the rack setting is much higher with the boosted engine as you found out.

No I don't have a pyrometer, I've quickly opened the hood after a very hard pull and the boost tube is cold as ice. I would have melted a piston if it had the exhaust gotten too hot.

I didn't want to re-invent the wheel, just needed more power because 39hp on a 5500 pound machine is not nearly enough.
To the guy with the new Kioti CK2610 machine, I have one and absolutely love it, a simple fuel rack adjustment will get you much more power, forget the turbo install, leave it alone and enjoy your excellent choice of machine. 425 trouble free hours now, I chose the gear version for simplicity.

Deezler...thanks!
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #99  
It all distills down to longevity far as I can see. If you can deal with a shortened life span (engine), go for it. If not, buy a bigger tractor (said that before).
 
   / Kubota L2501 Turbo: A Journey Defined - The Tractor, The Comparison, The Modification, The Results #100  
You should perform a leakdown test on your machine at some point as the turbo install will erode the piston ring land on the top ring only and compression will suffer especially if you use much power over sustained time. These folks will help you also.


I turbocharged my L3940 and it ruined all 4 pistons in 400 hours. Pull the part numbers of your pistons and compare with the actual turbocharged version, you'll see what I am talking about.

I have a thread here somewhere called "I still hate my tractor", it's about too many pages long, about my turbo install and experiences with it.

I have another 400 on it blowing snow wide open full tilt and have yet to have another issue but haven't done another leakdown test yet, again, perform a leakdown test not a compression test.
I stopped posting here much to the chagrin of the hall monitors here, only Elon Musk knows what I am speaking of; and yes I do still hate my tractor.

Another thread FRED and I mentioned your build post 89

If the engine already has the tougher Turbo spec pistons Ok , If Not it may be just a matter of time till that leak down increases.

 
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