Mitsubishi KE75 turbo retrofit how to/not to

   / Mitsubishi KE75 turbo retrofit how to/not to #1  

Ilikeurtractor

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Iseki TX1300F/TX1500/ TX2160F/TS2220F/ Satoh S370D/S373D
Well after some time pondering the whole turbocharging a factory N/A diesel and seeing a recent post (which I can't seem to find further information on another site which was referenced), I decided to try to adapt a turbo to a Mitsubishi KE75 engine to see how it would play out. At my elevation, I lose about 20% in peak power and torque due to the lower air pressure so just getting 3 psi of boost would help a lot and this is really my primary goal. Of course, I'd be ecstatic if I could make 6-7 psi of boost and try to do away with as much of the black smoke as possible on the high-speed end under load using the stock fuel settings - if that's how it will work - I don't know at this point but hopeful.

One of the first things I learned is that is isn't as straight-forward as I originally concluded to choose a turbo and I was a bit lazy in my original research, quickly deciding that any relatively small turbo "should" work. I chose a knock-off of a Garrett GT15 turbo for its price, availability, and size. Initial testing proved the engine is much too small for that turbo charger (apparently not enough flow to spin it enough to build any significant boost). I could just barely hear the turbo start to whine at about 2500 engine rpm with only slight improvement in spooling at 2800 rpm which is as fast as the governor would allow the engine to run. Even putting the engine under load at those speeds didn't seem to make much of any real difference in boost. It would not even budge the 0-15 psig gauge I had hooked up but I could feel some pulsating pressure on the line if I removed the gauge and held my hand over it.

Further research points to the possibility of an "IHI RHB31" turbo working better so I'm going to try that despite the project running quite over budget at this point. It appears to be the smallest turbo readily available so if it is still too big then I guess I'll be SOL for this project. I'll post the results when I get it swapped out.

Hopefully this thread can help others going down the same road and save them some time and money. I couldn't find a whole lot out there on similar sized diesels, but did read about some successful turbo adaptations (6-7 psi boost) on small Kubota tractors but with no real details on the turbo specifications. Since I now have the GT15 that I won't be using on this engine I may try to put it on an Isuzu 2AB1 (1.2L) engine in a Bolens G244 but I'm thinking that engine will still be too small for it. It looks like the GT15 is a good fit for (or was designed for) a 1.9L VW diesel. Seems as if engine horsepower plays into it also in addition to raw displacement but I can't find enough good info to wrap it all together.
 

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   / Mitsubishi KE75 turbo retrofit how to/not to #2  
Having been around Truck engines a lot ,I have just enough knowledge to know if the right turbo is not used . The engine will starve for exhaust pressure , heat from exhaust inability to escape , which could possibly do damage , under load use . It can be tricky to get the proper turbo for the right application .I experienced a wrong replacement of the turbo on my truck and it would have burnt the pistons up , if I continued to use it like that. You need a good relationship of fuel and air for proper combustion .possibly a motorcycle turbo might work . The problems arise whether you need to adjust fuel to compensate for the addition of air in the system. Kubotas may have a setup to use as a guide .Good luck ,sounds like a worthy project .
 
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   / Mitsubishi KE75 turbo retrofit how to/not to
  • Thread Starter
#3  
Thanks - not sure how worthy of a project for the cost, but certainly a big curiosity to me. From what I can gather, it seems turbocharging a diesel should be much more straightforward than a gasoline engine due to the gasoline engines inability to tolerate lean mixtures of fuel and air. Keeping that correct throughout the boost curve of a turbo would seem difficult without some sort of computer control and/or intake pressure feedback loop and fuel injection, but maybe it can just be done with a carburetor as-is (?) A diesel generally runs very lean, especially at idle, so pumping more air into it under pressure at any time doesn't seem bad until, I suppose, the peak compression pressures get to some "high value" shortening the life of the engine or blowing something like a head gasket or worse. I don't think I need to worry too much about getting to that point with the small selection of turbos for this size engine out there. I'm not planning to increase fuel at all, just help completely burn what I'm sending in. From what I can find one needs a ratio of at least 18:1 (air:fuel) to maintain clear exhaust and efficiently and completely burn the fuel and realize the associated gain in power. Of course, a diesel will apparently continue to produce more power as you add more fuel, just not very efficiently (past the black smoke point). I'm not a big fan of black smoke clouds everywhere I go but understand this brings additional power at the cost of efficiency and soot production. The exhaust backpressure issue is another concern as you mentioned. I have no idea when that may or will become a problem. Hopefully it won't come into play here.
 
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   / Mitsubishi KE75 turbo retrofit how to/not to #4  
From my understanding along with the more air ,more fuel will need to be injected until the turbo spools up smoke is a negative result . I believe what is needed is more fuel ,for the air that is present in the chamber to burn completely. Which is the reason a diesel truck engine throws black smoke at shifting cycles , waiting for the turbo to spool back up .I am no expert , just the way I understand what is happening . I had a Supercharger on a v/twin Harley ,It produced 10 LBS of boost , it needed considerably more fuel for the additional air that was put in the combustion chamber .
 
   / Mitsubishi KE75 turbo retrofit how to/not to
  • Thread Starter
#5  
I agree more fuel can be added as the boost increases and should be if one is seeking to increase the ultimate output of an engine. In fact I was surprised to learn that theoretical power output is directly proportional to absolute air pressure. I thought there might be a "diminishing return" concept happening where doubling the absolute air pressure might double the power, but tripling the pressure would not result in the triple the power but it will if you ignore heating effects from compressing the air and I'd guess some other things. So 10 psig of boost is actually quite a lot (a potential power gain of about 66% over a naturally aspirated engine at sea-level), even though I hear most modern turbo diesels run well over 20 psig and the pulling tractors do something in the 100-200 psig range or maybe even higher. However, I'm just shooting for sea-level performance at this point and maybe a bit better if there is still some excess fuel in the stock fuel delivery (at the full rack setting) that I can burn completely through increasing the air pressure (and density). Sounds like the Harley was working great. Maybe I should be looking for some sort of mini-supercharger :)
 
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   / Mitsubishi KE75 turbo retrofit how to/not to #6  
One thing I have noticed is Turbo Kits are high priced ,if they are made exclusively for a particular series of engines. I don`t want to discourage your goal of getting better performance from your tractor, but getting a system that will perform correctly may be time consuming and expensive , unless you can find someone that has succeeded in this endeavor ,that can offer some sound advice . My Harley enjoyed a 60% boost in power and torque . Ha Ha Ha , I have since sold it ,due to my health issues.
 
   / Mitsubishi KE75 turbo retrofit how to/not to
  • Thread Starter
#7  
If this smaller turbo doesn't perform well I'll pretty much be done because of the limited selections available that I know of. I'm guessing this smaller turbo should get me at least a couple of psi anyway, but maybe not. I do worry about the backpressure and how it may affect the engine though.

I was hoping to possibly "draw-out" others that may have tried this with similar engines but this project appears to have limited past participants. At least the results of this thread should help other curious people get some information and maybe in time there will be good, practical options for these engines if more turbos become available on the market that are reasonably priced for this application.
 
   / Mitsubishi KE75 turbo retrofit how to/not to #8  
If this smaller turbo doesn't perform well I'll pretty much be done because of the limited selections available that I know of. I'm guessing this smaller turbo should get me at least a couple of psi anyway, but maybe not. I do worry about the backpressure and how it may affect the engine though.

I was hoping to possibly "draw-out" others that may have tried this with similar engines but this project appears to have limited past participants. At least the results of this thread should help other curious people get some information and maybe in time there will be good, practical options for these engines if more turbos become available on the market that are reasonably priced for this application.

Have you done any reading on the topic?

A turbo charger can be "tailored" to the engine by changing out the turbine scroll. I'm no expert! Getting the Area and the Radius to match the exaust flow available from the engine can optimize the speed that the turbine spins.

You might be at a disadvantage using a less than fully supported turbine brand. The "famous makers" might be in a good position to suggest and offer a good combination.

I have one reference that I use for general information. It's from the 70's hot rod era, but all the details are covered. With the right combination of scrolls, You can get a pretty good coverage across engine displacements.

ps, You don't need any more fuel until you need to make more "horse pressure" than full injector timing will give.

WOW, This post sure came out differently than I thought it looked when it was typed. Sorry! I've edited the post now to make it at least readable. ;-)
 
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   / Mitsubishi KE75 turbo retrofit how to/not to
  • Thread Starter
#9  
Thanks for the info. I'm continuing to research this topic more and it certainly is much more complicated than I could have imagined. I'll be surprised if I end up with a working turbocharged engine in the end but not trying was getting the better of me...
 
   / Mitsubishi KE75 turbo retrofit how to/not to
  • Thread Starter
#10  
This appears to be some good general information on turbocharging. The section on myths is particularly interesting. I think the author makes a good point regarding boost pressure vs. air density. I think most people (certainly myself included) equate higher boost to higher air density. In reality I think this is mostly true but the heating of the air during compression has a significant impact on density. I read another forum post (sorry I don't remember the link) where a guy was getting around 8 psig of boost and claimed the engine had less power than without the turbo. Maybe this was why.

Turbocharger FAQ, VNT turbo FAQ, and turbo pictures
 
 
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