Add turbo

Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
Next tests while I'm waiting for a new gasket will be to add a 1/8npt port to the intake manifold to get a boost pressure reading and put a filter monitor on the intake pipe.
I have last year's air filter in the filter housing, I'm going to put a filter monitor on there called "the informer" to see how many inches of water vacuum the air intake pulls at peak.
Ideally a slightly used filter will have little or no inches of water reading.
If it maxes out I'll start looking for a bigger filter.
 
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Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
I haven't turned up the fuel at all.
I did end up finding the kubota exhaust gasket and put it on with some exhaust rtv. Now I have full drive pressure and and the kubota has so much raw power. I even popped the waste gate briefly.
The cooling system is filled with water and I did boil it slightly, have a 13lb radiator cap, so the boiling point of water is about 230°F at 4,400ft +13psi but the coolant gauge never went above 195. What I have to avoid is called nucleic boiling and that won't happen at 195°F under pressure.
Waste gating the turbo and boiling the coolant didn't happen at the same time.
 

ruger1980

Active member

Equipment
L4310 w/La682, L225
Oct 25, 2020
146
59
28
CNY
If you don't turn the fuel up you will see no gain in power. Power in a diesel is directly related to fuel delivery.
 
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Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
I definitely have way more power and I'm not rolling coal. Or if I do roll coal it's light and only when the turbo is getting spun up.
With my roughly 48 inch brush shredder the L185 was definitely under powered, with the turbo I don't find the L185 lacking power at all.
 
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ruger1980

Active member

Equipment
L4310 w/La682, L225
Oct 25, 2020
146
59
28
CNY
If you had sooty exhaust someone may have already messed with the fuel screw. That or your engine is worn enough you are not bringing in enough air or loosing it on the compression stroke. But as a rule a diesel will gain nothing by adding only more air. You have to have to add more fuel to gain any power
 
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Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
I have surprisingly little blow by.
Here at 4,400 feet up I'm lacking about 12% of the air they have at sea level. So I at least have that back now.
Also increasing compression does increase peak horsepower, it's only a few percent per full number increase in compression.
 

Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
Next turbo related mod will be to stick a 7 inch fan on top of the intercooler.
I'm not getting much air circulation with convection.
 

Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
It appears that a even a 200cc single cylinder diesel can spool a rhb31 turbo a little bit.
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
3,206
490
83
Mid, South, USA
for those that care to read.

RHB31's have at least 6 different variations (and probably a ton more). The variations are OE specified, so that the particular compressor and turbine are sized correctly to work with the OE application.

For instance an RHB31 is also on an M59. I have a couple of those. But it makes zero boost on a D722 (NA D722). Sure change the turbine housing right? Tried. The turbine wheel is larger than the smaller housing I got online (OE housing by the way). SO now I'd have had to change the shaft assembly, seals, bearings, o-ring, etc. Grand total if I got the parts retail is about $150 (and that was over a year ago, so probably $300+ now IF you can even get them)

I see this stuff all the time with automotive and powersports. Guys buy a generic turbocharger and toss it on, sure it makes 2x more power and they're happy with that. In under a year they're griping about ventilated blocks or wrecked cars or whatever. So sure you can absolutely make 20 psi, but what's the outlet temp? What's the shaft speed? Is the turbo rated for that speed? Is the shaft assembly and/or wheel(s) gonna come apart? What's the EGT? Whats the drive pressure?

How's turbocharging work (or forced induction in general)? It uses a device (turbo or supercharger) to increase the amount of air that is going into the engine. Anytime you increase pressure, you also increase heat. With that, your EGT can go sky high. Or it might not. Depends on the turbo, engine, inlet temp, and a bunch of other things. So for instance you make 10 psi with an outlet temp of 100 degrees F and a drive pressure of 10 psi. That's considered pretty good. Or, another turbocharger may make the 20 psi but at 250 deg F with a drive pressure of 40 psi. #1 is going to make way more power and a lot more reliably every single time.

So on any piston engine, the pressurized air does more than jsut stuff more air into the engine. Remember the engine has to ingest air on it's own without a turbo, via pressure drop on the inlet stroke. This takes crankshaft power to pull the piston down the hole against the rings, viscous drag, and in this discussion it also has to overcome in some cases a throttle blade which is restricting air movement, which I call parasitic loss. The turbocharger forces some air in under pressure which helps force the piston down the bore, which takes a lot of the parasitic loss away during the inlet stroke. At 0 psi boost, a turbo engine will make more power than a naturally aspirated engine which is also at 0 psi boost and 0 vacuum. But there's JUST the very beginning. Enter: drive pressure....

Remember the intake stroke is only 25% of the engine's workings. We also have an exhaust stroke. That's where the piston is forcing spent gases out of the engine. The turbocharger is in the way creating a restriction to flow which equals pressure. It takes more force to push those gases out on a turbo engine, thus it backs up and causes what I call drive pressure (the actual pressure inside the intake manifold). Remember the spent gases are hot and they can contaminate the intake charge. Additionally a lot of times the intake and exhaust valves are both open at the same time for a short period, any exhaust pressure will back up. It is inert and can't burn again and the burn does the work via expansion.

On a gas engine you have an intake tract, and most of the time the fuel injectors are placed at or near the end of the tract, but before the intake valves. In doing this, the fuel actually cools the intake valves, and when the valve(s) are open, the air/fuel mix (cool) helps cool the piston crowns and combustion chambers. On a diesel, you have air. You compress air and then really close to TDC fuel is injected into a prechamber (on most kubota's) where it almost instantly ignites, then the expanding gases are forced out of the prechamber and into the cylinder where the work is done. There is no fuel to cool the valves and piston crowns. Thus, drive pressure (hot) further heats the valves and crowns and also becomes a parasitic loss on the exhaust stroke. This is where guys can get into trouble not knowing what's actually going on. Most Kubota engines were specifically designed for atmospheric aspiration, and then there were some that were specifically designed for turbocharging. What's the difference? Grab your illustrated parts books, and compare the the differences. I'm too lazy today.


Going through this with my 2.3T swapped Mustang. Makes roughly 295hp with the stock turbo at 22 psi (TB0341). BTW stock boost on the SVO is around 15 psi, with a very restrictive intake (I cured that, and upped the boost). Calculating the airflow via mass airflow sensor, the stock TB0341 is spinning roughly 137,000 RPM at full boost and max engine speed. It is out of it's efficiency island at that point. Discharge temp at the IC inlet is 210, out of the IC at 132 is as high as I saw. So I called around and found out that the Borg EFR series of turbochargers are a much newer design and much more effiicient. So I bought one. Bolt-on for the most part (drain line was a little different). At 22 psi, it's making 346hp at the same 6000 RPM, outlet temp 172 and the air going into the engine is around 85. If I am lugging the motor, the TB0341 sends the boost gauge needle above zero at 1800 RPM, but its' about 2600 rpm before it's at full boost. The EFR? It is past zero at any hit of the throttle down to 1200 RPM (too scared to go any lower), fully lights quicker (2300 which honestly is too soon), is smoother (doesn't "hit" like an old 2 stroke dirt bike), quieter, and drive pressure is down from 51 psi to 27 which is significant and IMO impressive. Keeping all that in mind, a diesel doesn't respond quite that well as a gas burner does. Not without being able to get the right amount of fuel into the engine at the right time and actually be able to burn it. This is where the shape of the head, the type of "chamber", the shape of the piston crown, the intake and exhaust port designs, manifold, exhaust pipe/muffler, intake designs all come into play. Indirect injected diesels won't make the power that a direct injected engine will, but indirect's are quieter where direct's are louder but also extremely sensitive to piston/chamber shape/design. Mind you this is all in reference to single shot injectors, not common rail electronic. Electronic stuff opens up a whole other world in diesels. Now you can easily change timing, quantity, and a bunch of other things a LOT easier, too easy in fact, you can burn them down in no time flat. I've done it (at a training facility nonetheless....and if any of you reading this remember it from Fort Worth in about 2006, you just know what happened...LOL).

Indirect injected diesels in larger engines went away years ago in favor of more modern direct injected engines, that also use electronic control to run it. Indirects with mechanical injection are super limited in what can be done with them. And most Kubota's are just that, indirect, mechanical, and designed originally for atmospheric aspiration. The turbo engines, as said above, were designed that way from the get-go. So you take a D722 that had 16.5 hp using a manifold pressure of about 15 psi (atmospheric) and then you compare it to a D722-T which had a manifold pressure of roughly 21 psi, and made 21hp....but what we don't know is what the internal differences were? Even I don't know, because the D722-T was not a commonly available engine, and I ain't got no parts diagrams to compare parts numbers. Then we compare big trucks to Kubota's. Trucks have been electronic/direct for decades and "turning them up" was a simple matter of throwing more fuel to it (to an extent) at the right time. And they respond pretty well because the tuners can easily change it, and inexpensively. On mechanicals you change nozzles, pumps, pump timing, and a bunch of other stuff...not nearly as inexpensive or easy. Thus, again, IMO it's not cost feasible to take a N/A kubota engine and turbocharge it UNLESS you're in the hills and you just MUST have the power. Then you have to weigh the cost vs reward. Can that money be put toward paying the house or car off? Or do you have disposable income to play with?
 

Oil pan 4

Member

Equipment
L185 turbo
Sep 21, 2017
201
15
18
NM
I put a turbo and intercooler on my IDI non turbo diesel suburban, about 2013. No regrets, still runs great.

There appears to be no injection timing difference on idi boosted vs N/a idi diesel engines. N/A and boosted diesel engines normally use the same cams on the ones I have looked at and I can find parts diagrams for.

If you read any of the post you would see that I already calculated intake temperature and I'm using a gigantic intercooler on the kubota as far as the rhb31 and 700cc engine are concerned. The toyota mr2 intercooler was used on 2L 220hp cars. So I think it can handle cooling the air for a sub 20hp 700cc engine with ease.
So "what about all the heat" is a non issue.

Running N/A I bet it was seeing sustained 1,100 to 1,200F egt when it would roll coal, with the turbo I bet it rarely goes over 900. As I'm no longer rolling coal under heavy load.

If I wanted more fuel I could always run propane fumigation.

The next 2 mods are ready to go on, the 7 inch intercooler fan and a boost/vacuum gauge. I says alway use a boost/vacuume gauge even on a diesel as a slight vacuume can be a drive pressure or boost leak. I only discovered this purely by accident, I stuck a boost/vac gauge on my suburban until I could get a proper diesel boost gauge, well I quickly developed a drive pressure leak that showed up as 1.5''hg intake vaccum when accelerating. So I just always kept the boost/vac gauge on there.
 
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