L2501 Turbo: A Journey Defined - The tractor, The comparison, The modification, The results...

Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
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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.

Let’s begin.

My 2021 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 appearance and atmosphere 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, chip wood and unload miscellaneous large items from delivery trucks.
Thankfully, I have a Zero Turn mower 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. Friends, neighbors and co-workers familiar with my property quickly steered me away from such a small tractor and suggested I go bigger, much bigger. Most folks were urging me to buy a large compact or, small utility tractor. But that meant purchasing two machines, one for tractor work and one for mowing duties, which at the time, seemed unnecessary and rather expensive. Purchasing a smaller tractor with a Mid-Mount-Mower seemed to make a lot more sense. Further complicating my decision making ability was due to my ignorance and inexperience. I didn’t fully understand the limitations of a tractor’s size and weight. In turn, I wasn’t fully able to comprehend the recommendations that were being offered to me but, knowing these suggestions were based on decades of experience, I didn’t entirely disregard them. I just didn’t think a larger tractor was necessary.

After cross-shopping many brands and tractor sizes, I eventually made a decision purely based on my own incredibly vast inexperience and purchased a brand new Kubota B2601. I was proud of my decision since I technically bought a larger tractor than what I was originally planning to purchase, hence, appeasing those 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 as the tractor I was originally encouraged to purchase.

2601.JPG


Purchasing the B2601 wasn’t a horrible decision. It was a great tractor (which I still highly recommend) and served me well, but it wasn’t the ‘right’ tractor for my property and uses. The B2601 lacked the lift capacity, the size and weight required for removing stumps, carrying logs and heavy ground engagement work.

I’m sure most of us can agree, first hand experience is paramount. Nothing teaches you more than learning from your own mistakes. I welcome it. That said, I just hope my mistakes aren’t too costly physically, or fiscally. Luckily, this one wasn’t and within a year, I was once again visiting dealerships ready to purchased a larger tractor.

When you are in the process of tractor shopping, it’s worth repeating some very wise tractor 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 and cross-shopping multiple brands and tractors I was drawn to and eventually purchased the Kubota L2501 ‘Economy’ tractor.

2501.jpg


I purchased the L2501 for several reasons. First and foremost, bang-for-your-buck. You get a lot of tractor for the money. The L2501 also has an impressive track record for trouble free operation, build quality and reliability. Never a bad thing. Then there’s the combination of it’s size, weight, lift capacity and maneuverability. The L2501 is a real tractor made for serious tractor work. Furthermore, L2501’s engine (D1703-M-DI-E4B) also produces an impressive amount of torque for its size, especially considering it is naturally aspirated and delivers exceptional fuel economy. Having owned several overly complicated and expensive modern diesel powered cars, trucks and SUV’s, I appreciate simplicity. The L2501’s engine is a simple mechanical diesel and isn’t equipped with modern diesel emissions equipment, or electronics. Meaning it does not have a ECM (engine control module) or DPF (diesel particulate filter) and doesn’t require emission Regen’s which waste fuel and mandate high RPM engine operation. A huge bonus for sure! 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 intended uses. Plus, I was already familiar with the Kubota brand and I have a phenomenal dealer less than 40 miles away. Moreover, the L2501 was the tractor that many folks, including my dealer, originally recommended.
Whew! That’s a TON of good stuff! Sold!

2601vs2501.jpg


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

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Equipment
L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
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Naturally, I’ve spent quite a bit of time reading and researching the L2501 tractor. 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. Absolutely correct! But, come on! That’s pretty much expected from a budget economy tractor. Right?

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

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

The low engine power effects operating speed and slows the tractor down while running rear PTO implements, like a flail mower. 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 large 3-Point ground-engagement implements too, like box blades and land planes. The L2501 can lift and carry them without issue but, the larger implements can create too much drag and the tractor simply doesn’t have enough power to pull them 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 gears. 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 and forget trying to do any work in (H) gear. Basically, the (H) gear can only be used for transportation purposes, but most importantly, only on completely flat terrain! If not, the tractor will bog down and stall. Hills? Forget about it.

And, being naturally aspirated and having only 24.8 HP, the L2501 suffers 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 it is because it does things slower than I want, which leads me to believe there is room for improvement.
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 requiring 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, even in (M) gear. In the tractor’s present state, I think it would be impossible, for example , to power a flail mower, or even pull a box blade going up this hill, in anything but (L) gear.

I would really like to use a heavy duty commercial box blade. I don’t believe the L2501 has enough power to pull a heavy duty commercial box blade at my desired operating speeds. I would like to know that I have enough power and confidence in this tractor to use a larger, heavier box blade in challenging conditions.

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. Flat land and hills. 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.

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. You’re 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!!! Jackass!!!

Now, sell your embarrassing L2501 immediately and get a real tractor!!! One with power to spare!!! You’re welcome!!!

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, 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
 
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Rdrcr

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Equipment
L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
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Part 2: Evaluating the options

It’s true. I could just sell my L2501 and buy a new more-powerful Kubota standard L series tractor. The L3301, L3901, L3302 and L3902 all have more power and upgrading to a new tractor seems like it really would make sense. But, does it really make sense? Would purchasing one of these tractors be cost effective? Would purchasing a new tractor be the best option?

To determine that, I’ll need to examine the cost differences and performance advantages of each of the Kubota standard L series tractors (sorry, I’m excluding the L4701 due to it’s larger frame, size and weight).

The following information is based on 2022 Kubota Standard L HST 4WD specifications and pricing listed on Kubota’s official website at the time of this writing. I’ll be using the L2501 pricing and power figures as the baseline for the comparison. In addition, I’ll provide the PTO HP per dollar for fun. Why not?

The L2501 produces 24.8 HP and delivers 19 PTO HP ($963 per PTO HP).

The Kubota L3301 produces 33 HP and delivers 26.2 PTO HP ($799 per PTO HP). This tractor makes 25% more power and is $2,617 more expensive than the L2501.

The Kubota L3302 produces 33 HP and delivers 26.1 PTO HP ($912 per PTO HP). This tractor makes 25% more power and is $4,745 more expensive than the L2501. Ouch! That stings!
But, it’s worth mentioning, the L3302 is a very nice tractor and I for one really appreciate the new 02 series features, comfort and cosmetic upgrades. Okay! Back to comparisons!

The Kubota L3901 produces 37.5 HP and delivers 30.6 PTO HP ($754 per PTO HP). This tractor makes 34% more power and is $4,734 more expensive than the L2501.

And finally, the Kubota L3902 produces 37.5 HP and delivers 30.3 PTO HP ($860 per PTO HP). This tractor makes 34% more power and is $6,987 more expensive than the L2501. Brutal! But, like the L3302, it also is one heck of a nice tractor!

So, where does that leave us? Well, the L3901 has the best dollar per PTO HP at $754 and I obviously have plenty of tractor options to consider, that’s for sure. But, am I considering ALL the options? Is there something I’m missing?

I’m pretty sure I have a different mentality than most tractor and large property owners. I grew up in the city and had a father who had a passion for Hot rods and Muscle cars. That passion was passed on to me at an early age and I spent a lot of time early in life modifying and racing cars. Because of my experiences, I look at mechanical things a little different. The first question I ask myself is; can I make what I currently own better? Can it be modified in any way to make it perform better or, be more competitive? Can I apply the same automotive performance principles, to a tractor? Can the L2501 be modified to produce more power?

Well, yes. As a matter of fact, you can. And, I didn’t even have to experiment on my own, to figure it out. Several tractor enthusiasts and forum members have been enhancing their tractor’s performance in a variety of ways. I’ve been studying these projects and their progress for as long as they have been sharing them.

It’s been established that the L2501’s D1703-M-DI-E4B engine is detuned from the factory to meet Tier 4 emission standards. This same engine, in other applications makes a lot more power. Kubota detunes the L2501’s D1703 engine by limiting the engine RPM’s, retarding the injection pump timing and restricting fuel consumption.

We know how the L2501 compares against the other more powerful Kubota Standard L series tractors based on the brilliant cost vs. performance analysis expertly presented earlier. We also know some L2501 pioneers have modified their tractors and made substantial gains in power and performance for not much money. In some cases, no money. Their modifications simply cost time and nerve.

Ultimately, my decision to purchase a new tractor, or modify my L2501 will be established on cost vs. performance. Pretty simple. If it’s cheaper for me to buy ‘factory’ power and performance, that’s the direction I’ll go. If it’s cheaper and beneficial to modify the L2501, then that’s the direction I’ll go. So, what do these modifications and gains look like?

Let’s break it down.

The following performance data is based on actual independent PTO dyno results. I am simply using this data obtained from several sources as a basis to estimate the additional power these modifications can potentially produce. Your mileage may vary.

We know from the results of a recent PTO dyno session that an L2501 produced 31 HP and delivered 25 PTO HP modified with advanced injection pump timing and a fueling adjustment. That’s a 20% increase in power! And $733 per PTO HP! Essentially, this modification produces the same power and performance as a L3301/L3302, for FREE!!!
This of course, is assuming you poses the mechanical skill and understanding to perform this modification. But, did I mention it’s FREE?

By performing this modification on the L2501, you’re saving $2,617 over the L3301 and $4,745 over the L3302 and you’re rewarded with virtually the same performance. You can’t beat that! Period.

Hmmm, what if I want more PTO power? What about adding a Turbocharger? It took some time but, I found an example of a turbocharged L2501 that was also ran on a PTO dyno. This particular L2501 Turbo setup is only making 4 PSI. Regardless, this tractor produced 38 HP and delivered 31 PTO HP. That’s 35% more power than stock. Wow! That’s impressive!

The L2501 Turbo is virtually making the same power as the L3901/L3902 without any additional engine modifications. But, is there any cost savings? Yes indeed! Assuming a proper L2501 bolt-on turbo kit will cost roughly $2,500, you’re saving $2,234 over the L3901 and $4,487 over the L3902.
Moreover, the L2501 Turbo delivers a leading $674 per PTO HP!

A Turbo upgrade is starting to appear pretty tempting.

Can even more power be made? Yes! There’s another example of an L2501 Turbo with additional modifications. This tractor has been further modified with an increased RPM limit, an injection pump timing advancement, a massive fuel adjustment and a large Mitsubishi MHI TD03 turbo making 12 PSI. This particular setup hasn’t been tested on a PTO dyno. But, based on the the PTO dyno results that are available, I approximate this particular L2501 is making roughly 45-50 HP and 37-41 PTO HP! Heck, it could possibly be making even more power. Simply amazing!

Decision time.

It’s never that easy. As with anything in life, there are always compromises. Performing any of these modifications will void your tractor warranty (if applicable). Everything comes with a cost. So, you have to ask yourself, is it more important to have a powerful simple-mechanical-diesel powered tractor without emissions and no warranty? Or, is it more important to have a powerful tractor with a warranty and be forced to live with a complicated emissions system?

You decide! I already did.

I believe the case has been made and it makes more sense to modify my L2501 instead of purchasing a new tractor. But, which modification? The ‘free’ injection pump timing advancement modification, or a Turbocharger kit? Both options require a fuel adjustment and it’s hard to argue with ‘free’. So the choice between the two modifications in my opinion, comes down to performance goals, mechanical skill, nerve and cost.

The injection pump timing modification is a fairly involved process and requires the removal of many essential fuel and induction parts to gain access to the injection pump spacers that need to be removed in order to advance the injection timing. I’ll be honest, it’s a little scary. However, there are some great step-by-step instructions and videos available online to help anyone perform this modification successfully. If you’re looking for 25 HP at the PTO this might be the way to go! Did I mention it’s FREE?

As tempting as the injection pump timing modification is, I prefer uncomplicated and straightforward projects. A Turbocharger installation is a more uninvolved process by comparison. You’re basically just replacing the muffler and swapping some intake pipes. Easy! I’m definitely more of a parts-changer, than a professional, or even shade-tree mechanic.

I’m sure 31 HP and 25 PTO HP would be enough, but I’m looking for a little bit more headroom. Installing a Turbo should deliver at least 38 HP and 31 PTO HP and I believe that’s the increase in power I’m seeking. Plus, Diesel engines respond really well to turbocharging.

I’m going Turbo!

Mike
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
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Part 3: Turbo design, fabrication, installation and testing

My Turbo build begins on the heels of a couple very successful turbo setups already running on L2501 tractors. These particular Turbo setups encouraged me to begin the planning and research necessary to create my own Turbo system.

My goal is to design, fabricate, develop and install a turbocharger system that performs flawlessly on a completely stock L2501 tractor. My Turbo system will be designed as a straightforward bolt-on affair that can be installed with simple hand tools and basic mechanical knowledge. It’ll operate within the factory RPM range and at the optimal PTO RPM. It’ll enhance the performance of the L2501 without any further modifications.
It’ll be the ultimate L2501 attachment!

To achieve these lofty goals I’ve commissioned the help of a very good friend. He will be lending a hand and has a long list of automotive accolades and accomplishments in land-speed and custom Hot rod building. He is a former Indy car and V8 Supercar mechanic, engineer and fabricator. His assistance is needed as I simply do not poses the welding and fabrication skills required to bring this project to fruition. Having his assistance with this endeavor is a real privilege. I’m fully confident that together we will build an amazing Turbo system. Moving on.

With any small displacement engine, Turbo size is crucial, but with the L2501, it’s even more critical. Why? Because the L2501’s engine (D1703-M-DI-E4B) operates at such low RPM (2,400 maximum, 2,105 PTO). After speaking with several industry experts familiar with the L2501’s engine and it’s operating capacity, the collective minds decided on a brand new Mitsubishi MHI TD025 Turbocharger as the best option. It’s literally, the smallest Turbo I’ve ever seen.

Turbo.jpg


This tiny Turbo is somewhat undersized for the D1703’s 1.647L displacement and was originally designed for use on Kubota’s D1503 1.5L. This Turbo was chosen, however, because it’ll perform perfectly amidst the L2501’s low RPM operating environment. And don’t worry, this miniature Turbo can support up to 90 HP. Yeah. I think we’re good! With the Turbo decision behind us, I began looking at other components.

As with any project, quality materials are essential to success so I decided on using only high quality 316 and 304L stainless steel for all plate, tubing, clamps and adapters to ensure longevity and match the quality, reputation and reliability of the Mitsubishi MHI TD025 Turbo. Quite frankly, it wouldn’t make any sense to do otherwise.

In the very early stages of my research I read that the factory L2501 intake and air cleaner assembly is highly restrictive. Upon learning this news, I figured I’d replace the factory intake and fabricate a high flow short-ram intake along with a performance aftermarket off-road air filter designed to handle the extreme dusty conditions encountered in Baja and Rally racing.
So I did.

Intake.jpg


As I’ve mentioned previously, my big hill is my L2501’s nemesis. The tractor doesn’t appreciate the challenge and always struggles to make it to the top carrying a load. The custom intake noticeably improved the tractors ability to climb the hill in (M) gear. The newfound ability wasn’t anything earth shattering, the tractor still struggled, but the RPM’s would only drop a few hundred RPM’s, instead of several hundred RPM’s.

There were some drawbacks, however. The engine and intake noise was noticeably louder with the custom intake. I never thought to measure the increased racket but, I can tell you it was a little uncomfortable operating the tractor without wearing ear protection. And with further testing, I found there were some issues with air filtration. After many hours of hard use in dusty conditions, I found evidence of very fine dirt film in the intake tube. It’s probably nothing to be alarmed by but, I never saw any sign of dirt particles, or film inside the stock intake system. So, I removed the short-Ram intake and reinstalled the OEM intake assembly and air cleaner for piece of mind.

Due to the questionable air filtration properties found with the aftermarket performance air filter and the general assumption that a tractor will be used in dusty conditions, I knew I wanted my Turbo system to utilize the OEM intake assembly and air filter, even if it costs some performance (I’ll get to that later). Naturally, it’s much better to have superior air filtration protection than the alternative.

Roaring ahead with my thoughtful planning and ideas, I began to list additional design requirements and features we would be providing with this Turbo system.

I want my Turbo system to maintain a stock unmodified appearance. Meaning, I want to make sure all factory body panels remain in place and the Turbocharger system, including all piping and tubing components fit snugly under the hood, no cutting, modifying, or debauchery required. Moving forward with this “stock appearance” theme I recognized the importance of keeping the exhaust in the factory location. This will help keep the exhaust fumes away from the operator while running the tractor. I’m sure we all agree, this is a keen resolution. We’ll make it happen!

Next, we turned to mounting the Turbo on the L2501. I know, this topic sounds incredibly boring and ridiculously unnecessary but, it truly is an important consideration. The Mitsubishi MHI TD025 Turbocharger will not simply bolt on the L2501’s exhaust manifold. So, upon that hugely disappointing revelation, we had to decide to either fabricate a custom Turbo exhaust manifold, or make some type of an adapter to mount the Turbo to the factory exhaust manifold. An extravagant custom tubular Turbo exhaust manifold would be wildly awesome and incredibly impressive, but it would virtually double the cost of the Turbo system.
So, an adapter it is! Heavy sigh.

Most guys will simply make a “sandwich” adapter to mount the Turbo. It involves taking a piece of steel plate, drilling some holes, bolting it to the exhaust manifold and installing the Turbocharger on top. It’s cheap and effective. However, that’s not what we’re doing, we’re fabricating a proper adapter!

A mandatory requirement for my Turbo system is providing a provision for an EGT (exhaust gas temperature) probe, also called, a pyrometer. The pryometer will be used to monitor engine performance, engine health and fueling adjustments required for tuning purposes. The best location for the EGT probe is in the exhaust collector before the Turbocharger. This way, the probe can measure the temperature of all three cylinders together (not just a single cylinder) before the gases reach the Turbo. I realize this sounds easy but, it takes a lot of additional design, engineering and fabrication work to make a proper Turbo adapter. Fun! Not really.

Luckily though, the hard work will payoff as there are benefits if done correctly. For one, the Turbo inlet diameter and the exhaust manifold outlet diameter are rarely the same size. No surprise there. By installing a properly engineered adapter, we’re able to transition the tubing diameter gradually maximizing exhaust flow, improving velocity, resulting in faster Turbo response and spool characteristics, ultimately improving performance. Excellent!

Of course, all of these foolish ideas greatly effect the position and location of turbocharger which in turn, creates a ton more work. Wonderful! Not surprising, it took more time than planned but, we eventually got the adapter made and the Turbo properly positioned under the hood.

Adapter.jpg


The next big challenge was the Turbo down pipe and exhaust. All things considered, pushing the Turbo forward just a couple inches would make things so much easier. But, since we’re cheap bastards and I decided against building a fabulous custom Turbo exhaust manifold, moving the Turbo forward, is not possible. So it took a colossal amount time and effort to fabricate the down pipe and shape it in such a way to maximize performance, fit the tight confines under the hood with acceptable clearance and allow access to the mounting hardware. But, we did it! Thank heavens!
We’re very happy with the results.

Turbosystem.jpg


How about the Installation? What is involved? How long does it take? Can anyone do it?

It’s one thing to design, fabricate and build an entire Turbo system, but it’s another challenge to install it. We wanted to make sure the turbo setup is easy to install and remove, if necessary. The installation itself consists of several steps starting with the removal of the front loader, the hood and hood side panels. It’s a good idea to have a buddy help with the hood.

Hood.jpg


Once those obstacles are removed, you just need to remove the muffler, factory rubber intake pipe and CCV (crank case ventilation) hose. With those items in the garbage (stored in a safe place), it’s time to bolt on the Turbo adapter, followed with Turbocharger and the down-pipe assembly. Once these items have been bolted down, it’s time to install the intake piping. Can it really be this easy? Indeed! Install the new CCV hose to the engine crankcase vent tube and intake pipe and then place the vacuum plug on the intake manifold vent nipple. Now, install the Turbo oil drain and feed hoses.

Congratulations! That’s it! The entire installation takes about an hour. Honestly, I may have left out a step or two but common, it’ll take two hours max, if you’re totally unfamiliar with the tractor.

Overtop.jpg


Mike
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
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We made one rookie mistake regarding the design and fabrication of the intake charge pipe. We didn’t account for the hood prop-rod absorber and it cannot be reinstalled with the intake charge pipe in place, which means, no hood opening assist. Whoops! So, we’ll have to eventually redesign and fabricate a new pipe sometime in the near future. Shouldn’t be a big issue but, in the meantime, I’m using a shortened broomstick handle to keep my hood open when necessary. That’s the spirit!

Chargepipe.jpg


Ohhh, that’s right, I forgot one very important step required to complete the Turbo system installation. The fuel adjustment screw. Place palm on forehead. Unfortunately, this simple step can easily double the overall installation time.

By design, it’s not easy to gain access to the fuel adjustment screw. Kubota does not want you to do it, period. Tier 4 emissions, remember? The screw itself is hidden within a thick, heavy tamper proof protective security cover to prohibit access. Those of us that have ventured to remove this cover have found that it’s easiest to use a dremel. This is also the point of no return. Your warranty (if applicable) ends here.

Screw.jpg


It takes a bit of time cutting through the thick steel but, eventually, once you cut through the cover you’ll be able to get a flat head screwdriver inside the notch you made in the metal and twist off the cover. With the cover removed, fuel adjustments are quick and easy.

With the entire Turbo system installed and the fuel set screw accessible, it was time for some impressions and subsequent testing.

Systemdone.jpg


I gotta tell you, Turbo sounds combined with Diesel engine clatter are music to my ears. They’re made for each other. It’s like icing on a cake! The L2501 Turbo literally sounds like a mini-Cummins Diesel engine. Or, if you’re a Ford fan, a tiny 7.3L PowerStroke diesel. It’s hilarious. You can hear the turbo spool up and flutter down with throttle adjustments. Very cool!

How loud is it? There’s no muffler on that thing! Are you crazy? What about the noise? Shockingly, even without a muffler, it’s not loud. It’s about the same noise volume as stock, perhaps a tiny bit louder. The Turbo itself acts as a muffler for the exhaust and I believe using the OEM intake instead of an aftermarket air filter, also helps with the overall noise volume. I haven’t felt the need to use ear protection while running the tractor. Realistically, when you think about it, why would I bother? It would be a sin muffling the glorious sound when I’m so fond of all the new noises. Right!

Exhaust.jpg


With the Turbo system installed and the tractor running smoothly the time has arrived to see what this machine can do. Let’s get to work!

Mike
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
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WA
The L2501 Turbo is ready for testing and tuning!

To accomplish this task, I’ll be using a Pyrometer to analyze the exhaust gas temperatures. Why do we care about EGT’s again? What do they tell us? We’re using a pyrometer to test and tune the engine because the EGT is an indication of how hot the combustion process is in the cylinders and the amount of “after burning” that is occurring in the exhaust manifold. The pyrometer measures these conditions in real time. The EGT is also directly related to the air/fuel ratio and the general consensus is the leaner the air/fuel ratio is, the lower the EGT. And the richer the air/fuel ratio is, the higher the EGT will be. Therefore, in most cases, excessively high EGT’s means over fueling. Meanwhile keeping the EGT’s a bit leaner, will lower EGT’s and can actually improve fuel economy. Something to keep in mind. Most diesel experts recommend a maximum of 1,200-1,300 degrees of EGT and emphasize that you do not want to maintain temperatures above 1,300 degrees for any length of time. In theory, by using a Turbo to increase air flow in a diesel engine, fuel can be added in a calibrated manner to increase power while maintaining an acceptable air/fuel ratio that does not create excessive EGT’s. That’s the objective.

It wouldn’t be fair if I didn’t include a baseline EGT test. So, without further delay here are the EGT readings I recorded when 100% stock.

L2501 HST 4WD (LA525 Loader w/ 66” QA Bucket, Liquid Tire Ballast) - ALL STOCK, NO MODIFICATIONS (40* ambient temperature).

Recorded EGT’s:
Idle = 200-300*
Traveling on flat ground (M) = 300-500*
Loader and grading work (M) = 500-700*
Traveling up hill carrying medium load (22* Slope, 40% grade) (M) = 600-738*
Peak EGT = 738*

Now, let’s compare the Turbo EGT’s but, with the factory fuel setting. NO ADDITIONAL FUEL HAS BEEN ADDED. We just installed the Turbocharger system and ran the tractor.

L2501 HST 4WD (LA525 Loader w/ 66” QA Bucket, Liquid Tire Ballast) - TURBO SYSTEM - 4PSI - Factory Fuel Setting (83* ambient temperature).

Recorded EGT’s:
Idle = 250-275*
Traveling on flat ground (M) = 275-500*
Loader and grading work (M) = 500-625*
Traveling up hill carrying medium load (22* Slope, 40% grade) (M) = 575-700*
Peak EGT = 700*

As you can see, nothing really has changed. The EGT’s heat up a bit quicker but, overall, the temperatures are running around 0-75 degrees cooler with the Turbo installed combined the factory fuel setting. I’m assuming this is because there is more air getting forced into the engine with the same fuel volume. Right now, with the Turbo and factory fueling, there is zero smoke coming from the engine, regardless of conditions. The engine is using all the fuel it can get.

We’re just getting warmed up!
Let’s add some fuel!

I started with a 1/2 Turn, counter clockwise to increase fuel volume. This setting resulted with a peak of 6 PSI and 3 PSI of sustained boost pressure. No smoke was observed during testing and surprisingly, EGT’s dropped under load going up the hill in (M) gear. Strangely, maximum EGT observed was 631 degrees. Weird.

More puzzling, I wasn’t happy seeing only 3 PSI sustained and I began questioning why I wasn’t maintaining more boost pressure. Was it fuel? Or, was it something related to the Turbo system? At this moment I started questioning the capacity of the OEM intake assembly and air filter. Could it flow enough air for the Turbocharger? I quickly removed the OEM intake assembly and ran the Turbo open-air (no filter) to see if the factory air intake assembly was causing a restriction.

The tractor did in fact pick up an additional 1 PSI of boost both peak and sustained with the same fuel setting, but only 1 PSI. 1 PSI isn’t monumental. This proved a few things; one, using the OEM air cleaner assembly and filter is perfectly acceptable. Two; with such a small gain in boost pressure, it isn’t worth using an aftermarket performance air filter, especially considering the air filtration issues. And three; I need more fuel. I reinstalled the OEM air cleaner assembly and prepared for additional testing.

I gradually increased the fuel volume to 1 full turn, counter clockwise. This setting resulted with 7 PSI peak and 4 PSI sustained boost pressure. No smoke was observed during testing. That’s not enough sustained PSI. I still wasn’t pleased with the results.

L2501 HST 4WD (LA525 Loader w/ 66” QA Bucket, Liquid Tire Ballast) - TURBO SYSTEM - 7 PSI - Fuel setting, 1 Full Turn (75* ambient temperature).

Recorded EGT’s:
Idle = 275-300*
Traveling on flat ground (M) = 300-500*
Loader and grading work (M) = 500-630*
Traveling up hill carrying medium load (22* Slope, 40% grade) (M) = 500-640*
Peak EGT = 640*

I then increased the fuel volume to 1 1/2 turn, counter clockwise. This setting resulted with the same 7 PSI peak but, 5 PSI sustained. Now we’re getting somewhere! There was some smoke observed at startup and a puff or two during operation. Not bad. I was happy to be making progress, but, still unhappy with the results.

L2501 HST 4WD (LA525 Loader w/ 66” QA Bucket, Liquid Tire Ballast) - TURBO SYSTEM - 7 PSI - Fuel Setting, 1 1/2 Full Turns (82* ambient temperature).

Recorded EGT’s:
Idle = 250-300*
Traveling on flat ground (M) = 300-500*
Loader and grading work (M) = 500-630*
Traveling up hill carrying medium load (22* Slope, 40% grade) (M) = 500-641*
Peak EGT = 641*

Shockingly, the numbers really aren’t that different. Why? I just can’t place enough load on the tractor to make it work hard enough to sustain boost pressure. Even going up my big hill in (M) gear carrying a load isn’t enough to maintain a load on the tractor. Crazy!

Continued on Post #22!!!

Mike
 
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jimh406

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Kubota L2501 with R4 tires
Jan 29, 2021
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I don't know what you are calling high elevation, but my house is about 4400. My L2501 works fine here.
 
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tractorX

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KUBOTA L2501 DT 5' BOX BLADE 42" FORKS PIRANHA TB 5' BUSH HOG 6' GRADER
Sep 27, 2013
75
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Rock Spring GA.
great write up mike!
really enjoyed following your tubo mod. 👊
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
351
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WA
I don't know what you are calling high elevation, but my house is about 4400. My L2501 works fine here.

Please keep in mind this particular comment isn’t based on my own personal experience but, rather complaints that I’ve read from current and previous L2501 owners.

I’d say 4,400 elevation qualifies as high. And, I’m happy to hear your tractor is performing admirably.

Mike
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
351
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WA
Part 2 is up. Post #3.

Mike
 

B737

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this is so awesome, I can't wait for the additional content!!
 
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radas

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2022 LX2610HST
Mar 21, 2022
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Excellent summary so far, I appreciate the detail and thought process in arriving at your conclusions. Look forward to updates.
 
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ken erickson

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B7100 hst, 2650 front mount snowblower, L2501 hst qa loader
Nov 21, 2010
494
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Waupaca Wisconsin
Where did all the information go?
Great Reading-Thanks!
Mike has added info to “part” 1 and 2 with remaining parts yet to come.
i assume that Mike did it this way to keep all 4 parts at the top of this thread?
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
351
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63
WA
Mike has added info to “part” 1 and 2 with remaining parts yet to come.
i assume that Mike did it this way to keep all 4 parts at the top of this thread?
Yes, that is correct!
I wanted all the initial content on the top of the thread and the follow up material afterwards.

I'm still working on Part 3.
I hope to have it finished soon.

And, for those that are curious the tractor and turbo are performing and running fabulously!!!

Mike
 
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trueg50

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B2601
Jul 1, 2020
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22
3
Vermont
As a B2601 owner that might have gotten too small a tractor, this certainly has me interested.
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
351
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63
WA
As a B2601 owner that might have gotten too small a tractor, this certainly has me interested.
I've been there! It really depends on what you're doing with your tractor. I just needed a bit more lift capacity and weight to accomplished the tasks I'm doing. I'm very happy with the L2501...and even more happy with the L2501 Turbo!

Mike
 
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Mountainhill

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l2501 (l3800 2013/22), Box Blade, post hole digger, Leon's rear blade
Apr 3, 2017
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Appreciate all your work to prepare and share the information you’ve gathered.

Can a 2501 Turbo Kit be purchased or is it a customized process/project.
 
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Rdrcr

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L2501 Turbo (Current), B2601 (Sold)
May 7, 2021
351
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63
WA
Appreciate all your work to prepare and share the information you’ve gathered.

Can a 2501 Turbo Kit be purchased or is it a customized process/project.
You’re welcome!

We haven’t finished making all the jigs yet, but the Turbo kit will be available to those that are interested.

Mike
 
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