AdeOlly
Well-Known Member
I'm having an issue with the port engine which has defied all the easy and obvious fixes; hopefully somebody can think of something I haven't before I give the nod to my engineer to start pulling bits apart.
Scenario is as follows. Power up from tickover both engines pull cleanly, evenly, and power the boat over the hump. As the revs yomp away I throttle back to 3000 rpm which is my usual cruising rpm giving 25 knots. Engines briefly settle and then port engine gradually starts to drop rpm, eventually to the 2700 rpm mark when the kompressor cuts in and gives the engine a kick and revs back to 3000, whereupon the whole cycle starts again. Starboard engine manages to maintain its 3000 rpm. This is with engine sync turned off, if left on then starboard engine follows the port down, as EDC matches stbd revs to port engine. Now, If rather than throttling back to 3000 rpm I set the revs to 3100 rpm or higher, then all is normal and no loss of rpm. I maintained a 3200 rpm 28 knot cruise all the way across Poole Bay a couple of weeks ago on a blissfully calm and sunny morning.
I have done no less than three sea trials, one with engineer who had electrical gubbins connected up. Boost pressure is slightly lower on port than starboard, but he 'thinks' not enough to cause the issue we're seeing. The issue started about three months ago and has gradually become worse, but is now at a consistent level.
* Props have been cleaned and are free of all weed/slime/barnacles etc. (Having done this after an earlier trip that day when they were a bit fouled the performance difference was nothing short of astounding)
* Fuel filters are clean
* Air filter replaced
* Boat's bum is clean (I spent an enjoyable hour anchored up in Priory Bay on one of those recent hot days with the deck brush and snorkel brushing off what little slime there was)
* There are no error codes recorded on the ECU or evident when issue occurs
* There is no smoke from exhaust, even if I flatten the port throttle when it's losing power, which to me implies the ECU knows something is amiss... and doing this makes no difference to engine performance or sound
* Engineer has listened intently to the engine at various speeds and is sure there is no hosing or injector problem, or any other unusual noises coming from it.
* The turbo boost pressure sensor was replaced four years ago, but in any case we are seeing sensible readings on the diagnostic kit so assuming its okay
* I have cleaned the connectors to the EDC throttle pots, which themselves are only three years old after a similarish problem with starboard engine
* I think (not easy to be 100% sure with iffy french fuel gauges) the port engine is burning more fuel, which engineer says makes sense as ECU is trying to get the revs up and thus fueling up the engine. (Note - no black smoke so ECU is doing this within specs)
Other point of note are that it's not entirely consistent. Last week messing about with the throttles, up down, start, wot rpm, the issue seemed to go away and I cruised back to Pompey at 2900 rpm across both engines. Stopped near the entrance and headed back out.. and the issue was back. Electrical ??
Engineer thinks that the aftercooler may be partially blocked and thus engine not receiving sufficiently cooled air to develop enough power to maintain rpm. This is the next step unless anybody has any bright ideas..... If aftercooler is clear, then off with the turbo.
Ideas?????
Scenario is as follows. Power up from tickover both engines pull cleanly, evenly, and power the boat over the hump. As the revs yomp away I throttle back to 3000 rpm which is my usual cruising rpm giving 25 knots. Engines briefly settle and then port engine gradually starts to drop rpm, eventually to the 2700 rpm mark when the kompressor cuts in and gives the engine a kick and revs back to 3000, whereupon the whole cycle starts again. Starboard engine manages to maintain its 3000 rpm. This is with engine sync turned off, if left on then starboard engine follows the port down, as EDC matches stbd revs to port engine. Now, If rather than throttling back to 3000 rpm I set the revs to 3100 rpm or higher, then all is normal and no loss of rpm. I maintained a 3200 rpm 28 knot cruise all the way across Poole Bay a couple of weeks ago on a blissfully calm and sunny morning.
I have done no less than three sea trials, one with engineer who had electrical gubbins connected up. Boost pressure is slightly lower on port than starboard, but he 'thinks' not enough to cause the issue we're seeing. The issue started about three months ago and has gradually become worse, but is now at a consistent level.
* Props have been cleaned and are free of all weed/slime/barnacles etc. (Having done this after an earlier trip that day when they were a bit fouled the performance difference was nothing short of astounding)
* Fuel filters are clean
* Air filter replaced
* Boat's bum is clean (I spent an enjoyable hour anchored up in Priory Bay on one of those recent hot days with the deck brush and snorkel brushing off what little slime there was)
* There are no error codes recorded on the ECU or evident when issue occurs
* There is no smoke from exhaust, even if I flatten the port throttle when it's losing power, which to me implies the ECU knows something is amiss... and doing this makes no difference to engine performance or sound
* Engineer has listened intently to the engine at various speeds and is sure there is no hosing or injector problem, or any other unusual noises coming from it.
* The turbo boost pressure sensor was replaced four years ago, but in any case we are seeing sensible readings on the diagnostic kit so assuming its okay
* I have cleaned the connectors to the EDC throttle pots, which themselves are only three years old after a similarish problem with starboard engine
* I think (not easy to be 100% sure with iffy french fuel gauges) the port engine is burning more fuel, which engineer says makes sense as ECU is trying to get the revs up and thus fueling up the engine. (Note - no black smoke so ECU is doing this within specs)
Other point of note are that it's not entirely consistent. Last week messing about with the throttles, up down, start, wot rpm, the issue seemed to go away and I cruised back to Pompey at 2900 rpm across both engines. Stopped near the entrance and headed back out.. and the issue was back. Electrical ??
Engineer thinks that the aftercooler may be partially blocked and thus engine not receiving sufficiently cooled air to develop enough power to maintain rpm. This is the next step unless anybody has any bright ideas..... If aftercooler is clear, then off with the turbo.
Ideas?????
