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| Author |
Message |
    
Lucca Toti
New member
Username: lucca
Post Number: 2
Registered: 02-2007
| | Posted on Monday, February 26, 2007 - 06:20 pm: | 
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After years of trying everything and anything I just decided to ask this to the forum:
I have a pair of 6V53TI (400HP) on a Hatteras 41' fishing / SCUBA diving boat. The engines are not new (I'm not first owner) but they used to work decently some 5 years ago until they started with black smoke emissions.
After that, I've repaired each motor twice. I've changed injectors (remanufactured) three times and have had the turbos inspected, cleaned and repaired twice. No success. Black smoke is still there.
It seems the transmission works well...
Last technician who saw the engines (tech service of DD is basically non-existent here in South America) recommended me to buy "brand new, original injectors". I'm trying to do that and that's why I psoted a message on this board earlier.
I read something about black smoke on a different DD engine and everybody said it may be caused by poor air intake. I'm not sure what should I do to make sure that's not my case (I simply don't trust the technician anymore).
The engines work basically well until they run at aprox 1100 RPM. After that, I have to increase RPMs VERY little by little to avoid the smoke. It works only 1 out of 5 times but I cannot go over 2100 RPM...
Any help!
Thanks. |
Capt William Myers
Visitor
| | Posted on Tuesday, February 27, 2007 - 01:38 pm: |
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Black smoke usaully means to much fuel, but it might be that the diesel fuel is not pure or is carrying to much water. Change filters, take a sample of the fuel and have it tested if possible, if not, put in diesel fuel dryer, and certan octane booster. |
Darel McCormick
Member
Username: sardog
Post Number: 8
Registered: 02-2006
| | Posted on Tuesday, February 27, 2007 - 05:49 pm: |
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There could be a lot of problems causing this but one thing I can tell you is its a severe one. Your situation tells me you're not combusting the fuel correctly. That is caused by too much fuel, not enough air, low compression, or an overload situation.
First, too much fuel: Make sure you have the correct injectors installed. Check the engine data plate against what's actually installed. There are numerous types of injectors that will fit but the engine is tuned for only one set. Make sure the tech is timing the injectors to the correct setting IAW the manual.
Second, not enough air: Remove the silencers and clean out the catch screen on the inlet to the supercharger (roots blower). I will assume you don't have the airsep system but if you do make sure they are still serviceable and clean. I know this will sound silly but check your air intakes to the engine room. I have found critters nesting in there that have starved the engine room of air that had everyone scratching their heads. Next pull an airbox cover on the side of the engine and peek in there. It should be free of debris especially at the liner intake holes. You'll know what I mean when you look inside. Make sure the remainder of the covers are tight and not bleeding air out of them.
Third, low compression. The best way to check this is with a compression tester. But if you have lots of white smoke at idle after warm-up, your rings are probably tired, especially if you have some blue smoke mixed in.
Fourth is an overload: Your props need to be perfectly clean and not at all dinged or bent. Bottom should be clean and barnacle free. You would be surprised how little it takes to cause big problems on a planing hull. Has the boat been repropped and unknowingly were the wrong pitch abd diameter installed.
If you have no joy with the above then the only way to truly diagnose the engine is with a fairly inexpensive handheld digital manamoter and digital phototach. I know that probably sounds scary but it's actually quite easy. Detroit has tons of operating paramaters published at various engine speeds. After installing a couple of fittings at specified locations on the engines, you take the various pressure readings on the intake, exhaust, and crankcase ports in inches of water, inches of mercury, or psi which all are available on the digital manometers. Compare them to the published specs and pinpoint the problem.
Doing anything else will be parts changing and cost you many more times than the cost of some simple test equipment.
And about the injector reccomendation, that's baloney. Detroit remanufactured is fine and reliable. What you do have to watch for is the age of them. Don't use any over 6 months after rebuild. There will be a date on them of the rebuild. You should also try to get a matched set. By this I mean each injector is tested as to its actual output. Not all N-70's are exactly 70 cc's. Detroit offers a "matched set" option when purchasing to have all 6 injectors to the same output calibration. But I can tell you that you have something much, much bigger going on than injector cals. Good luck! |
arvil johnson
New member
Username: propnut
Post Number: 2
Registered: 03-2008
| | Posted on Tuesday, March 04, 2008 - 10:11 pm: |
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Im not really sure but i think the TI stands for turbo inter cooled , and if im not mistaken its configured like a71 or 92 series with the inter cooler under the blower.someone help me here, If so if its never been cleaned it needs to be. |
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