Hi Folks,
Recently, the subject of turbocharged Kubota engines has come up repeatedly.
I am in the market for an older, 20th century, L-series tractor, and have become somewhat obsessed with what opportunities might exist for that tractor to be powered by a turbocharged 4-cylinder engine.
Why? I don't have a defensible reason for my preference, it's really just a whim, at this stage. But, I have been highly motivated to do some research on this topic, and that's what I want to share here.
I started by asking a question - "What Kubota L-series tractors were produced in the 20th century with turbocharged 4-cyinder engines?" For the US market, the answer is simple: "None." For the "gray market", the answer gets more interesting. I have found three or four Kubota tractors produced for non-US markets that were factory-equipped with turbocharged 4-cylinder engines:
- L4202 (1978-1985)- came equipped with the VT1502 engine, rated at 42hp, in contrast with the non-turbocharged V1500, V1501, or V1502 rated at about 35hp.
- L1-435 - equipped with the V1512-DI-TI-N engine(?), rated at 43hp
- L1-43/GL43 - equipped with a 4-cylinder turbocharged engine, unknown model
Here is an L4202 data plate:
One can search these model numbers in youtube, and find videos of them in operation, mostly in southeast Asia. I'm not sure if the V1512-DI-TI-N or V1512-DITC engines seen in these videos are factory-installed, or transplants. The V1512 engine was also used as a stationary powerplant (irrigation pumps, generators, etc.).
I have obtained a Parts List for the L3202 and L4202 tractors, and it includes part numbers for all engine parts for the non-turbocharged V1502 and the VT1502. What are the differences in these two engines? Besides the obvious (turbocharger and turbo compensator), they are:
- cylinder head casting
- piston and piston-ring assembly
- crankshaft
- connecting rod bearing [connecting rod part numbers are the same.
I am guessing that the crankshaft is different in that the rod journals are radiused, thus requiring a different connecting rod bearing. I have attempted to document the differences between the turbo and non-turbo cylinder head and piston. Here's what I have found:
V1502/1702/1902 Cylinder head casting (non-turbo):
VT1512 Cylinder head casting (turbo, 15345-03040):
It is easy to see the important difference here. The non-turbo head is an Indirect Injection head, with a spherical pre-chamber ported into the combustion chamber between the valves. The turbo head is a Direct Injection head. The injector nozzle protrudes through that chamfered hole between the valves.
Here are the two pistons:
The top piston is for V1512 (non-turbo) and the bottom piston is for the V1512-T. Notice that valve reliefs are missing from the turbo piston, and that it has a bowl in the top. The injector nozzle is centered in that bowl. Strangely, the injectors for the V1502 and the VT1502 in the parts list are apparently, the same (see below).
At this point, I want to introduce a very informative scientific review paper which discusses the engineering intricacies of turbocharged diesel engines. The title is: "A review of design considerations for light-duty diesel combustion systems" The two co-authors are at Lund University (Sweden) and Sandia National Labs (Livermore, CA).
Here is a link to the paper:
www.osti.gov
My favorite quote from the paper is:
"Thousands of man-years of effort have been expended in balancing multiple trade-offs as such basic parameters as compression ratio, bore-to-stroke ratio, and combustion chamber geometry are selected."
What I learned is that there are intricate design features of the piston bowl (into which the injector spray is placed) and its companion injector which have profound effects on the efficiency of combustion. Also, the piston height is greater in the turbocharged motor - it is what is known as a "quench" motor, where the piston approaches to within 0.6-0.8 mm of the cylinder head. This allows heat to more efficiently be transferred from the piston to the cylinder head and its water jacket. The space between the piston margins and the cylinder head is unavailable for combustion. The purpose of the bowl is to create "swirl" in the cylinder to improve mixing and combustion efficiency. The injector spray pattern must be carefully matched with the piston bowl.
Besides the piston and cylinder head design differences (turbo vs non-turbo), Kubota injector pumps are different for turbocharged engines. There is a turbo compensator, which adds additional fuel as boost increases to maintain the proper fuel-to-air ratio. I am not sure if the timing of Kubota injector pumps can be finely adjusted, but I know that it is infinitely adjustable with turbocharged Cummins motors. Timing should be retarded for turbo motors, because combustion is a more rapid event under the conditions of higher cylinder pressures and swirl.
Bottom line here is that simply slapping a turbo on a non-turbocharged engine ignores ALL of this...and is thus, a fool's errand. YMMV.
Yeah, it'll make a cool noise, but will it make more power?
Practically speaking, I see no opportunity to properly convert a non-turbo engine to turbo.
SO, then what???
Given that it would be very difficult or even impossible to get my hands on one of these gray market tractor models, and ignoring the challenges of parts support, what else can be considered?
I'm starting to think more and more about opportunities for engine swaps to turbocharge a non-turbocharged tractor model. It's attractive to consider the prospect of installing an entire engine to grab all the matched turbo-engine features at once.
What I'm looking to document now is the differences between the mounting systems at the bellhousing between readily available, domestic turbocharged Kubota engines, and the tractors I might want to install them in. So far, I've sifted through skid-steer loaders, to find the turbocharged 4-cylinder Kubota engines. Here's what I've found:
Bobcat 773 (1994-2001): V2003-T-E2B (46hp)
Bobcat S160 (2005-2013): V2003-M-DI-T (56 hp)
Bobcat S185 (2002-2013): V2003-M-DI-T (56 hp)
Bobcat S205 (2005-2013): V2403-M-DI-T (61 hp)
Bobcat S550,S570 (2013-present): V2403-M-DI-T (61 hp)
There are other Bobcats with larger turbocharged engines (V2607-T, V3307-T, V3800).
Yesterday, I looked at a Bobcat S185 and a S205 side-by-side. Interesting that, on the V2003 motor, the injector pump is on the right (radiator) end of the engine, and with the 2403, the injector pump is on the left (flywheel) end of the engine.
My thinking is that, if the bellhousing mounting pattern can be made to fit (modified or adapted), other things (like engine mounts, radiator location) are relatively easy.
-Paul
Recently, the subject of turbocharged Kubota engines has come up repeatedly.
I am in the market for an older, 20th century, L-series tractor, and have become somewhat obsessed with what opportunities might exist for that tractor to be powered by a turbocharged 4-cylinder engine.
Why? I don't have a defensible reason for my preference, it's really just a whim, at this stage. But, I have been highly motivated to do some research on this topic, and that's what I want to share here.
I started by asking a question - "What Kubota L-series tractors were produced in the 20th century with turbocharged 4-cyinder engines?" For the US market, the answer is simple: "None." For the "gray market", the answer gets more interesting. I have found three or four Kubota tractors produced for non-US markets that were factory-equipped with turbocharged 4-cylinder engines:
- L4202 (1978-1985)- came equipped with the VT1502 engine, rated at 42hp, in contrast with the non-turbocharged V1500, V1501, or V1502 rated at about 35hp.
- L1-435 - equipped with the V1512-DI-TI-N engine(?), rated at 43hp
- L1-43/GL43 - equipped with a 4-cylinder turbocharged engine, unknown model
Here is an L4202 data plate:
One can search these model numbers in youtube, and find videos of them in operation, mostly in southeast Asia. I'm not sure if the V1512-DI-TI-N or V1512-DITC engines seen in these videos are factory-installed, or transplants. The V1512 engine was also used as a stationary powerplant (irrigation pumps, generators, etc.).
I have obtained a Parts List for the L3202 and L4202 tractors, and it includes part numbers for all engine parts for the non-turbocharged V1502 and the VT1502. What are the differences in these two engines? Besides the obvious (turbocharger and turbo compensator), they are:
- cylinder head casting
- piston and piston-ring assembly
- crankshaft
- connecting rod bearing [connecting rod part numbers are the same.
I am guessing that the crankshaft is different in that the rod journals are radiused, thus requiring a different connecting rod bearing. I have attempted to document the differences between the turbo and non-turbo cylinder head and piston. Here's what I have found:
V1502/1702/1902 Cylinder head casting (non-turbo):
VT1512 Cylinder head casting (turbo, 15345-03040):
It is easy to see the important difference here. The non-turbo head is an Indirect Injection head, with a spherical pre-chamber ported into the combustion chamber between the valves. The turbo head is a Direct Injection head. The injector nozzle protrudes through that chamfered hole between the valves.
Here are the two pistons:
The top piston is for V1512 (non-turbo) and the bottom piston is for the V1512-T. Notice that valve reliefs are missing from the turbo piston, and that it has a bowl in the top. The injector nozzle is centered in that bowl. Strangely, the injectors for the V1502 and the VT1502 in the parts list are apparently, the same (see below).
At this point, I want to introduce a very informative scientific review paper which discusses the engineering intricacies of turbocharged diesel engines. The title is: "A review of design considerations for light-duty diesel combustion systems" The two co-authors are at Lund University (Sweden) and Sandia National Labs (Livermore, CA).
Here is a link to the paper:
A review of design considerations for light-duty diesel combustion systems. (Conference) | OSTI.GOV
The U.S. Department of Energy's Office of Scientific and Technical Information
www.osti.gov
My favorite quote from the paper is:
"Thousands of man-years of effort have been expended in balancing multiple trade-offs as such basic parameters as compression ratio, bore-to-stroke ratio, and combustion chamber geometry are selected."
What I learned is that there are intricate design features of the piston bowl (into which the injector spray is placed) and its companion injector which have profound effects on the efficiency of combustion. Also, the piston height is greater in the turbocharged motor - it is what is known as a "quench" motor, where the piston approaches to within 0.6-0.8 mm of the cylinder head. This allows heat to more efficiently be transferred from the piston to the cylinder head and its water jacket. The space between the piston margins and the cylinder head is unavailable for combustion. The purpose of the bowl is to create "swirl" in the cylinder to improve mixing and combustion efficiency. The injector spray pattern must be carefully matched with the piston bowl.
Besides the piston and cylinder head design differences (turbo vs non-turbo), Kubota injector pumps are different for turbocharged engines. There is a turbo compensator, which adds additional fuel as boost increases to maintain the proper fuel-to-air ratio. I am not sure if the timing of Kubota injector pumps can be finely adjusted, but I know that it is infinitely adjustable with turbocharged Cummins motors. Timing should be retarded for turbo motors, because combustion is a more rapid event under the conditions of higher cylinder pressures and swirl.
Bottom line here is that simply slapping a turbo on a non-turbocharged engine ignores ALL of this...and is thus, a fool's errand. YMMV.
Yeah, it'll make a cool noise, but will it make more power?
Practically speaking, I see no opportunity to properly convert a non-turbo engine to turbo.
SO, then what???
Given that it would be very difficult or even impossible to get my hands on one of these gray market tractor models, and ignoring the challenges of parts support, what else can be considered?
I'm starting to think more and more about opportunities for engine swaps to turbocharge a non-turbocharged tractor model. It's attractive to consider the prospect of installing an entire engine to grab all the matched turbo-engine features at once.
What I'm looking to document now is the differences between the mounting systems at the bellhousing between readily available, domestic turbocharged Kubota engines, and the tractors I might want to install them in. So far, I've sifted through skid-steer loaders, to find the turbocharged 4-cylinder Kubota engines. Here's what I've found:
Bobcat 773 (1994-2001): V2003-T-E2B (46hp)
Bobcat S160 (2005-2013): V2003-M-DI-T (56 hp)
Bobcat S185 (2002-2013): V2003-M-DI-T (56 hp)
Bobcat S205 (2005-2013): V2403-M-DI-T (61 hp)
Bobcat S550,S570 (2013-present): V2403-M-DI-T (61 hp)
There are other Bobcats with larger turbocharged engines (V2607-T, V3307-T, V3800).
Yesterday, I looked at a Bobcat S185 and a S205 side-by-side. Interesting that, on the V2003 motor, the injector pump is on the right (radiator) end of the engine, and with the 2403, the injector pump is on the left (flywheel) end of the engine.
My thinking is that, if the bellhousing mounting pattern can be made to fit (modified or adapted), other things (like engine mounts, radiator location) are relatively easy.
-Paul
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