AD31 suspect turbo problem

[Viscount]

Got out yesterday. All OK initially (2+ hours and 30nm or so) but noticed latterly lack of power from port engine. Tried each engine separately and got 8kts from starboard (normal) and only 6kts from port. Together under load, starboard would rev to 3,400 RPM but port struggled to get to 3,000 RPM. Temperatures both normal. Turbo whine not evident from port. Took off air filter to check turbo would spin by hand which it did. Any advice as to what I should do now?

 

[moonraker 36]

fouled prop?

 

[Viscount]

Sorry, I should have mentioned that; I lifted the drives and props looked fine. Thanks for the thought.

 

[Pendana]

Remove the exhaust elbow and check the clearance between the turbine blades and the turbine housing. Any more than about 2mm and the exhaust gasses will start to bypass the turbine and go straight to the exhaust which means the turbo doesnt spool up to the correct speed.

If you have to go down the relacement turbo route there is an upgrade turbo for the 130hp AD31. Not quite sure what the upgrade is, I assume it spools up quicker - perhaps others might chip in and tell us, but you have to would have to do both engines of course.

Good Luck

 

[ulyden]

Measure the boost pressure first. Check the smoke limiter hose. If no smoke check fuel supply first.

 

[Latestarter1]

Measure the boost pressure first. Check the smoke limiter hose. If no smoke check fuel supply first.

Thank you ULYDEN pleased you chimed in, all getting repetitive. I cannot understand why at the first sign of a problem people start performing like a Catherine Wheel with the pin pulled out! Just like plumbers, refuse to call them heating engineers, troubleshooting defective boiler, replace the most expensive component first and work backwards.

Data data data, leads to correct and COST EFFECTIVE diagnosis. http://www.ybw.com/forums/showthread.php?t=254828&page=2

Question not answered in the other thread so I will ask again 'when were charge air coolers last serviced?)

Also your WOT rpm on GOOD engine seems low IF the posted numbers are real.

 

[Viscount]

Measure the boost pressure first. Check the smoke limiter hose. If no smoke check fuel supply first.

I'm note sure what the "smoke limiter hose" is. I have checked the exhaust brake and it's working properly.

I assume the "charge air cooler" is the aftercooler. It was last serviced (replaced actually for a new one) in 2004 (400 engine hours ago). I didn't consider it as the change in performance happened so quickly. Is it just a matter of taking the top off and cleaning out?

The starboard WOT of 3,400RPM is low but that's because the port engine is not performing properly. On the initial run referred to, both engines gave 3,500 and would have gone further if I had used WOT.

Since posting earlier, I have changed the fuel filters and also tried feeding the problem engine from the other tank. I also tried running briefly without the air filter. I checked each cylinder to the extent that I slackened each fuel feed in turn to check that the engine note changed which it did for all 4 (I appreciate that's hardly a thorough test but it was all I could think of).

The only additional "clue" I have is that after running the engine briefly today, I tried to spin the turbo from the air filter side to find it stiff. It would turn but would not continue turning after I released. Running the engine again seemed to resolve the issue but I am surprised that after an hour of so of turning the engine off, it would be as stiff as that.

I do not have access to a gauge and frankly not sure how to use one anyway.

To compound matters, I now have a hydraulic leak on the starboard drive lifting system. I cannot therefore go out until the pipes are changed which look like a contortionist is required. However, when comparing the engines just revving without load, the starboard is noticable quicker to respond to throttle than the port. Both do however have a tendancy to hang around at 3,000 for a moment before going futher and, when they do, this is where the port seems to take longer to react.

 

[ulyden]

Boost limiter is a device at top of fuel pump. Its a membran limiting fuel when boost pressure is low. Try to give you a picture. Check fuel suply is more than filters. You have a fed pump and a suction line and maby a kind of grid in the tank. Measure the fuel flow comming back to the tank. It shuld be more than fuel wot consumption at 3500rpm with no load. If not, you have a problem. You are right in the wot speed on second engine if speed is to slow
it wont reach normal wot speed. If you run both engines at 3000rpm is boat speed normal then?

 

[Latestarter1]

Diagnosis over the internet is pointless without proper #’s

ULYDEN is trying to help you check out the logical route of fuel = heat = boost.

Unless you are prepared to invest a small amount in the most basic tools makes more cost effective sense to engage proper technician who does. Local hydraulic hose supplier could make up a simple kit with nipples hoses and a 0-50 PSI gauge for about £30 in order to check fuel pump and boost pressure. Digital tacho should be part of ships gear now that they have become so cheap. http://cgi.ebay.co.uk/DIGITAL-RED-L..._Measurement_Equipment_ET&hash=item483ca9f613

Your head seems intent on turbocharger replacement and you MAY be correct, you have not mentioned engine hours. Modern turbochargers are robust and durable and see no reason why it will normally last to engine overhaul unless they have been compromised by poor installation (unlikely in an outdrive installation) or poor maintenance. Engine hours have not been quoted.

A no load snap throttle test gives zero indication as to how engine actually performs under load and you have not posted high idle #s which you have obtained. People seem scared of taking a diesel engine out on to the governor droop and holding it there until the governor stabilises, just let the motor sing to you. To understand how your engine performs under load take a look at the Bosch cutaway and, if you Google Bosch LDA which is the correct name of what is being referred to you will understand exactly how the pump/turbocharger function.

I think that the heading in your original post holds the key, AD31 suspect turbo problem, gives us a clue to your mind set I do not think that you will be happy until you have ripped the turbo off and that you were actually looking for some input to endorse your intended course of action. For my part I cannot accept people approaching simple troubleshooting in such a half assed manner.

 

[Viscount]

ulyden, thanks for your reply. When I have the hydraulic leak sorted, I will try both engines at progressive speeds and note the results; forecast is for flat seas, so it might be possible.

Latestarter1, I have no desire to rip off the turbo or anything else. The engine hours are 1,100; you may take that as both a mention and a quote.