Instruments for diesels

Discussion in 'Diesel Engines' started by tranmkp, Jul 14, 2008.

  1. tranmkp
    Joined: May 2002
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    tranmkp "wherever you go. there you are"

    Can I have a good explanation why someone would need a cylinder head temp gauge and an exhaust gas temp gauge on their setup?

    thanks
     
  2. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    To monitor what is going on in those two positions, both critical to tuning and running an engine correctly.

    i am referring to "real' engines, where tuning and running the engine is controlled by the operator, not electronic controlled engines and high speed wizz bangs.

    In a slow or mid speed engine the fuel supply is controllable to each and every cylinder independantly. Each cylinder has its own injector pump, and this is tunable from the rack that connects them all to the throttle lever.

    By observing the exhaust temperature for instance, you can see how hard that cylinder is working , it is the exhaust temperature, not the position of the injector rack at the injector pump that the cylinder is tuned. By adjusting the injector pump, you arrange all the exhaust temperatures to be even, that way each cylinder is pulling an even load on the engine. If the cylinder was tuned simply by the position of the rack on the injector pump, the loads could be entirely different in actual life output. A lazy cylinder would remain as such and not be identified, putting uneven loads on the rest of the engine.

    The cylinder head temperature is another display of the amount of work that the cylinder is doing, once the exhaust temperatures have been set as even as possible, the engine is then running balanced, the cylinder head temperatures should be very similar, any deviation from norml will show up very quickly, and may need other attention, things like leaking valves etc will also be identified as well as leaking head gaskets.

    There are a million other reasons, but this will give you a good idea of why these two critical gauges are required.
     
  3. masalai
    Joined: Oct 2007
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    masalai masalai

    Landlubber, thanks for your explanation and informative advice. Could you please indulge this "dummy from the dungeons".... I am looking at using the Lombardini LDW 1003 engines which seem to have injector pump on the top of each cylinder head for each piston... If they are adjustable, as you say, and the appropriate temperature sensors are fitted, is there a particular temperature that should be aimed for? is that EGT related to the type of fuel (normal Australian Diesel or "preheated coconut oil") and or compression ratio? - The engines are to be used as gensets and run around 2000 rpm... (see http://www.polarpower.com/products/generators/3-8kW Lombardini 1003 for marine micro cogen or 7 kW to 10 kW Diesel water cooled generator with 6255 alternator)
     
  4. Landlubber
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    Landlubber Senior Member

    Mas, I am still in Shanghai, and cannot connect to many web sites here (China policy), so could not get the Lombardini site you mentioned.

    My understanding of this engine is that it is air cooled, they are not high end engines, so you get what you pay for. You state the models youa rare looking at are in fact water cooled, this is basically essential for a live aboard boat. The injector pump will certainly have to be adjustable, as the stroke of the pump is what controls the amount of fuel that the cylinder receives, diesels are not controlled by air inlet as is a petrol/carby engine but by the amount of fuel they are given, the air is a constant/per swept volume of the cylinder.
    You say the genset runs at around 2000rpm, this is a strange speed for a "normal" genset as the electric alternators run at 1500 or 3000 usually (all because of the windings and the phasing), so i reckon it will be at one of those two. The slower the speed the longer the life of the engine, so try to get a genset that is the 4 pole type on 1500rpm. It is a lot more peaceful listening to it also.

    I guess that you will be living on board, i would suggest that you look into inverters. You should be able to live on a lesser powered genset by good use of an invertes/charger system. I have lived for many years on boats, and found that i could run my genset for 1/2 an hour every morning abd night and still keep the freezer down to 17 deg within that time. Also did the water heater at the same time, so the load was full for the period being run.
    This system was supplemented with 4x 60w solar panels, run without regulators. I only once ever went flat, and that was my fault, I left the radar on as well as the autopilot one night and forgot them. Easily fixed of course by starting the genset, but normally never needed except for the times stated.
     
  5. masalai
    Joined: Oct 2007
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    masalai masalai

    Thanks Landie, - - - Assumptions :D:D - - - I should have said DC to charge batteries at 72 or 96 volts depending on electric engine choice (ASMO Thoosa 13000 or 17000 x two) and other services will use inverters for "domestic services" or 12/24v DC for nav.... OK leave it till you get back then a PM or ???
     
  6. lazeyjack

    lazeyjack Guest

    the exhaust pyro is often used on large trucks too, when an engine loads and the temp goes to a certain point, you downshift, at 900 degrees
    the exhaust pyro gauge can be switched on the ships engine to measure each cyl head temp, if one injector is plugged the temp will be very low
     
  7. Landlubber
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    Landlubber Senior Member

    no Mas I live in Shanghai at present, building boats there.
    You can pm me if you so desire anytime mate.
     
  8. Landlubber
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    Landlubber Senior Member

    Yeah lazyjack, my old girl has pyros in each exhaust outlet, the modern way of course ids to use a sender, the low temps shown show that the cylinder is being lazy, not doing its fair share of the work, and really being a bludger in Aussie talk, so we have to balance the loads on the poor 'ol crankshaft if we want her to be in harmony.

    In fact, when my old MAK was tuned nicely (balanced exhaust temps) she would blow perfect smoke rings straight up and in perfect linear order. very pretty to watch. Then we can start on setting the racks up.
     
  9. masalai
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    masalai masalai

    OK landie, Just your lack of access to the data. Only a "toy" sized engine but technologically quite neat, and meets my needs nicely (quite narrow and light)
     
  10. lazeyjack

    lazeyjack Guest

    there are many great threads in here abt onboard power, masalai you shud do a search, it get kindsa tiring saying it all over, no offence here
    But really a quick answer, it all boils down to money
    the ideal setup is the biggest batt bank you can accomadate(pocketwise and room wise) the batt bank is the inverter fuel and the best is TRACE , THEN a quality genset that matches both
    On 24vdc a 4000 watt inverter/charger will need a bank of 750 amp hour , thats abt 800 lbs batteries, this will need a 6 kw genset min . this size inverter will start motors(fridge) run computers and microwave
    May I suggest you work back from that and never ever go for a high rpm genset:))like a bloody panda, see the things in every workshop anywhere piled into a corner
    best are, northern lights and Onan
     
  11. tranmkp
    Joined: May 2002
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    tranmkp "wherever you go. there you are"

    very interesting comments - I was familiar with a rotary switch setup for cylinder head temps but was clueless about a similar setup with the exhaust, I assumed you would just have a single sensor downstream and not just outside the header.
     
  12. masalai
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    masalai masalai

    The few occasions I have seen is close to the head so each head can be measured.... - - nearly all aircraft engines have EGT sensors - seem to be about half way from exhaust valve to where the pipes merge....
     
  13. Landlubber
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    Landlubber Senior Member

    The exhaust sensor is not far from the head, it is in the full flow of the exhaust from the head. Too far away and it would not show the high temps that actually exist there.

    Hey remember the ad for Chrysler slant 6 in the 70's, that red hot engine was soooo impressive.
     

  14. FAST FRED
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    FAST FRED Senior Member

    A CHT is of little use on a liquid cooled engine.

    An EGT is the best way to NOT overload the engine .

    A properly setup engine will usually not need one , but a CPP, damage to the prop or drive, loosing a cylinder , or just a filthy bottom the EGT will be of great use.

    FF
     
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