Diesel Exhaust Gas Temperature

[Zanshin]

I am thinking of putting an EGT gauge on my Yanmar and using the temperature to ensure that I don't overwork my engine. I have a Gori prop with a cruising mode which, if run at too high RPM, could end up overheating the engine (I've done that before) and think I could use the EGT to adjust the RPMs to an optimal value.

Has onzone here actually used EGT on a marine diesel?

[sailak]

My only experience with EGT has been on aircraft engines...and used only to adjust fuel/air mixture.

I would think manifold pressure or BMEP would be a better way to measure power/workload on the engine.

[negrini]

Once you measure the backpressure at SWOT, it will never change (unless you clog the exhaust somewhere), so BMEP at manifold (??? not sure how to use it there !!) will not tell you what you want. This is a fixed theoretical measure, not counting on propeler load. I never used a market EGT, but used the VOLVO accessory installed right after your manifold, for that on my previous boat (MD2040). Used to quickly imdentify high temp on engine, by measuring exhaust temp, you clearly will get alarms for temp increase waaay earlier than water temp gauge. A good achieve if something has clogged the water colling system. But to adjust rpm<>load ..... best is to keep engine at peace revs

[Zanshin]

The "cruising mode" propellor setting at 2500rpm in calm waters is fine, but the same rpm in medium swell at sea (can) cause overheating. I can't overheat the diesel with normal setting, but get significantly less mileage and speed in that mode. Thus I am looking for a way to dynamically adjust my RPMs and not to overheat or overload the engine and can only think of the EGT between the exhaust manifold and the turbocharger. I know this is used a lot in trucks to get optimal performance, but since I can't adjust the AFR in the Yanmar I was thinking (again) of using the exhaust temperature. I did have a diesel mechanic in St. Martin tell me it wasn't necessary, but he wasn't the one whose engine alarm went off while trying to get through Antigua's English Harbour before darkness set in

[negrini]

hummmm, an Autoprop would adjust itself ? Providing a variable pitch to self-adjust to the load ? When you say "dynamically adjust" you mean an automated adjustment ? I think the EGT at your manifold would provide a rasonable source of heating measure, reliable, and fast enough to not overheat engine, but your engine will reduce rpm for other reasons other than just overload, and response might be somehow slow. Another source could be your engine's governor so you can have a sense of load posing resistance to your drivetrain. I think you should measure the governor and balance with rpm (compared at no load). A simple (mechanical) solution would be more elegant .... I think.

[Zanshin]

negrini - I meant that I would adjust the RPM so that the system didn't overload/overheat, nothing mechanical or automatic. And I don't mean changing the settings continually, but finding the highest setting for a given wind/wave/sail combination. Right now I really can't tell unless I wait the 10-15 minutes after making a change and if the water temp alarm doesn't go off then I'm still OK...

[dieselboy]

Originally Posted by Zanshin

negrini - I meant that I would adjust the RPM so that the system didn't overload/overheat, nothing mechanical or automatic. And I don't mean changing the settings continually, but finding the highest setting for a given wind/wave/sail combination. Right now I really can't tell unless I wait the 10-15 minutes after making a change and if the water temp alarm doesn't go off then I'm still OK...

With respect i must say that you may not be looking at the big picture.

While a EGT will give you advance warning of an pending over heat. You should not be running that fine line to begin with. That is a very dangerous and costly game to be played.

I would recommend taking a step back and examining the whole situation.
If your load is causing an over heat then look in to the cond of the cooling system. sea pump, air relief line on the head to remove any steam or air,location of the air up take," is it breathing in hot air from the exhaust", does it also have a water pump? t-stat? how smooth does the engine run? do you have weak fuel inj's causing fuel to be injected in in a stream not at a high pressure " fog" this causes hot spots..
Factors like these are what you really need to be looking in to.
just remember that the two biggest and most common death's of Diesel engines are over heating and water contamination.. Your doing one right now..

[Zanshin]

I am trying to do this in order to ensure that I don't overheat the engine. The engine is more than sufficient to plug away at 2500rpm all day when the propellor is in normal mode, which gives me 6ish knots. If I motorsail in the so-called "overdrive" mode the same RPM gives me 8 knots or more with the same fuel consumption. What I am trying to find is as high an RPM setting that I can cruise with when necessary without undue stress to the engine. My Yanmar panel only has an enginer overheat light but nothing to give me advance warning that I am approaching that point.
I wonder if a cooling water temperature gauge would be simpler to install and could give me the same information, albeit somewhat slower.

[dieselboy]

Install a direct feed " non electric" it will give a real time temp feed just mount ti where you can see it.

[jrd22]

I'm not familiar with the Gori, but from what you said it seems that in "overdrive" mode you must be lugging the engine which will lead to an early death. Can you reach the recommended WOT rpm's when in overdrive? If not, then it is the same as having the incorrect prop installed. If I am missing something regarding the situation please let me know, but you can't have increased speed through the water at the same rpm without a change of pitch or diameter of the wheel. The exception would be the Autoprop, which automtically adjusts pitch based on rpm and boat speed, and load.