Turbocharging a diesel engine?

Discussion in 'Diesel Engines' started by Jonny88, Dec 3, 2010.

  1. Karl2
    Joined: Feb 2005
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    Karl2 Junior Member

    Have a copy of Mr. Bell’s book and I agree, well written and a wealth of information. I have enjoyed it immensely.
    When I buy and turbo charge my Alfa Romeo 1750 Berlina this book will be my bible (Yet another project that I will go to my grave wishing I had done).
    His book about Supercharging is equally well written and informative.

    Mr. Bells book deals with gas engines and to a large extent some pretty extreme applications and references (800 hp V8’s, 1.000 hp F1 engines etc. etc.). The principals and theories covered in the book are relevant for turbo charging in general (Gas & Diesel) but there are some fundamental differences (Absence of air volume control (throttle plates) in a diesel, the need to maintain your fuel/air mixture in a narrow stoichiometric band in a gas motor, the need to design yourself out of pre-ignition in a gas motor, the typical diesel cam having less overlap, etc. etc.)

    I highlighted in my previous post “…in the context of this post…”.
    The original post stated: “….turbocharging of diesel engines. Looking more at large installations for ships and things…”. Given the original post and my assumptions (Dangerous, I know) regarding the author of the posts intent (Moderate power increase ?) I maintain that any relationship between intake and exhaust manifold pressure is irrelevant.

    Karl2
     
  2. Submarine Tom

    Submarine Tom Previous Member

    It depends a hell of a lot on how much boost pressure you are using (intake).

    -Tom
     
  3. Karl2
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    Karl2 Junior Member

    I maintain that in the context of the question from the original post the relationship between exhaust pressure (Before the turbine) and intake manifold pressure (boost pressure) is irrelevant.
    And, again, with the original post in mind "Looking more at large installations for ships and things" this would not be an application where you would design and deploy a waste gate turbo system. You would select the appropriate "fixed" turbo and the boost pressure curve would be what it would be.

    But for the sake of good discussion and exchange....
    This could become an issue if the pressure before the turbine dramatically exceeds the boost pressure. Even at that it would only become an issue during valve overlap. In a production diesel engine this overlap is very short.

    In modern production and high performance diesels it is common to run max boost at 30 psi, 40 psi and even higher. Combine this with the short overlap and you will find that you don't have an issue.

    Should the boost pressure exceed the pressure before the turbine you have a very good thing and, according to Mr. Bell (and in reference to gasoline engines): "..you can begin to make serious power..."

    If the author of the original post were to move forward with his project and find at the end of the day that he has an issue with these pressures it means that he has completely missed the boat with his turbo charger selection. He has selected a turbo completely unsuited for the application - The pressure issue would be only the top of the iceberg, he would be faced with a number of issues related to this turbo selection - At least the turbine section of the selected turbo to small, will probably exceed specified max turbine speed resulting in the turbine coming apart, bearing/shaft failures etc. etc. The compressor side of this turbo would probably be too small too resulting in low boost and dismal power/efficiency gain.

    Karl
     
  4. copenhagen
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    copenhagen Junior Member

    Forget all the articles on turbocharging gas engines... on a diesel you can easilt add a turbo without worrying about compression ratios, but you do have to change the injection timing to keep the EGT down.

    In an ideal world you would change the pistons to turbo pistion to lower the compression down into the 18-22:1 range but you can run stock ones without issues at moderate boost levels
    the cheap option is to cut valvereliefs in the pistons (you can rent the tool from most engineshops)
    If you are running an injectionchamber diesel like a toyota 2L you should get a turbo head.. but the above fix is fine (valve reliefs also allow you to have the cam reground to a more aggressive lobe)

    in a car or truck its important to run a turbo specific injection pump as the load isnt closely related to RPM, but in a boat its not as important.

    but if you just add a turbo, keep the boost below 10 psi and retard the injection point at load to a point where the egt is arround 850 F you shouldnt see much deteriorated fuelefficiency at low load.. and a 30% powergain at load with less than 30% increase in fuelconsumption (the reason for this is if your torbo is sized right you will have more increase of pressure on the cold side than on the hot, resulting in reduced pumping losses

    and yes ive done it myself on a toyota 2L (including the cam change) and the above is a parafrase of what ive learned... (final lesson : 40 psi boost and propane injection will kill a toyota)

    PS: sorry for my spelling but im using a new laptop and the keyboard is just not compatible with my fingersize
     
  5. astat101
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    astat101 Junior Member

    Turbo charging a diesel engine.

    Hi,

    I know that this is an old post but I would like to input where I can. I work for a company called vestas aircoil who design and manufacture large diesel engine charge air coolers. I note that you are talking about turbo charging a diesel engine, well consideration has to be made to the charge air cooler also for this. when the turbo compresses the air, it is important to cool this air down prior to entering the engine and mixing with the fuel. The cooler the air, the more dense it becomes which increases the oxygen content which improves combustion which allows more fuel to be burned.

    So we can say that the performance of the turbo works hand in hand with the charge air cooler.
     
  6. DennisRB
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    DennisRB Senior Member

    I have read that turbochaging naturally aspirated diesel engine will result in no power gain, unless the injector pump is rebuilt with the capacity for more fueling so it can burn the extra air the turbo provides. However some standard pumps have enough adjustment on the screw to get some extra power.

    I have been toying with the idea of turbocharging my 3GM30 yanmars when I do a refit. I have turboharged petrol engines before and this seems a lot easier. I would not bother with an intercooler as I would only run around 10psi. Intercoolers are great on diesles too but much less important than on petrol engines due to detonation which will destroy a petrol engine quite quickly. I just wonder if my standard injector pumps have enough adjustment to give extra fuel for it to be worth the hassel. Its a huge cost to get pumps modified, but the turboharging system is actually very cheap.

    I was hoping for some more top speed and better economy which would come from the ability to run larger props.
     
  7. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Here is a good article on marine turbo-diesels.
    http://www.passagemaker.com/articles/technical/engines/to-turbocharge-or-not-to-turbocharge/

    This I found most interesting, as I would have thought the opposite to be the case, that you could get a greater operating range...
     
  8. DennisRB
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    DennisRB Senior Member

    That snippet is pretty low on technical information.

    "There is not enough turbo energy to give the boost to burn the fuel"

    Are they saying that there will be an excess of fuel causing smoking, high EGT and carbon build up? I guess that probably would be bad, but that seems to be a tuning issue more than anything else? There is no requirement for there to be an excess of fuel just because the turbo has not built boost yet with a well tuned system. However I can see that in the real world with crude injector pumps rather than computer control this scenario might happen. But don't most turboed diesels also have a boost line going to the injector pump to prevent this sort of thing happening?
     
  9. Jamie Kennedy
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    Jamie Kennedy Senior Member

    I think in theory there is a lot of development that could take place. The intercooler could be used to generate your hot water, even boil your water for tea and bake your turkey. For powerboats that are designed to be able to plane but also want to be able to cruised below hull speed to conserve fuel there is a need for a better range of power. Traditionally this is done with multiple engines which is still a good option, but I would think that with some development a marine diesel engine could be developed that can shut down cylinders and switch between natural aspiration and turbocharging. For power-sailing there is an even greater need for a range of power, along with cheaper variable pitch propellers. I think diesel-electric hybrids might be the way to go.

    I think for small and medium sized boats especially there is still a great need for the technology to be simple and maintainable, without too much electronics and computers controlling the engine and generator systems. I don't mind computers as long as I am allowed to know what they are doing and I can maintain them myself. Perhaps I am wrong in this respect. Anyhow if it was myself I would opt for whatever engine and systems are easiest to maintain for what I needed it for, and if I needed more range of power I would go with two or three engines versus one, or some sort of a diesel-electric hybrid system.
     
  10. DennisRB
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    DennisRB Senior Member

    "The intercooler could be used to generate your hot water, even boil your water for tea and bake your turkey."

    The idea of the intercooler is to drop the air temp down as low as possible. If the water leaving the intercooler is hot enough to cook a turkey the inlet air temps must be very hot still. Better off using the engine coolant system if you want play with systems like that.
     
  11. whitepointer23

    whitepointer23 Previous Member

    Engine electronics are not that scary. You can purchase diagnostic software for your laptop for most engines. Everything is plug and play. Its not hard to carry a spare ecm and a few bitz and pieces in your spares kit. But in reality engine electronics are very reliable. I used to be stuck in the last century too. But after a few years of owning and driving electronic diesels without a problem I am sold on them.
     
  12. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Thanks for that. Good to know.
     
  13. astat101
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    astat101 Junior Member

    Hi, I work for a company that design and manufacture charge air coolers for large diesel engines and it is noted that changing the turbo will have an impact on the charge air cooler. you will need to consider replacing the charge air cooler, this will cool the compressed air from the turbo.
     

  14. astat101
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    astat101 Junior Member

    Hi,

    Just thought I would add some info. to this. I work for a company called vestas aircoil who design and manufacture charge air cooler for large diesel engines. I would like to add that If you are looking to install a turbo charger then you will need to have consideration to the charge air cooler. The hot air coming from the turbo will need to be cooled prior to entering the engine to maximise the combustion. The cooler the air, the more dense it becomes which increases the combustion.



    I may be able to assist with any questions, I work for a company called Vestas aircoil who design and manufacture charge air coolers. If you are looking into a turbo charge, you will need to look at cooling down the air that comes from it before in enters the engine. Cooler air better combustion better performance.
     
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