Volvo Penta D6-350 Performance Issue and Black Smoke

[Lax207]

Good day Folks!

Need your assistance here with a bit of an issue we have been having on our 2007 Cranchi 41' Endurance using 2x VP D6-350/DPH's with about 410 hours on both engines.

In general, both engines work just fine and reach their desired WOT as specification. A current problem we are facing is just when both engines are accelerating, the supercharger kicks in at 1500rpm and pushes the boat to 2200rpm's, and thats when the turbo takes over.
However for the port engine, it reaches 2200 rpm but then drops down to 2000 rpm as if it does not have enough boost and power to carry on. You could see on the video attached that the turbos boost is there, but as soon as it hits 2200rpm, boost and rpm goes down for a few seconds before turbo boost is built up again slowly and it continues to accelerate. During this few seconds of 'stalling' black smoke is emitted form the engine. During this stall, the starboard engine continues to perform and accelerate with no issues.

Link to video: https://drive.google.com/file/d/0B-Wh7zHONGeXVTdqcjNqbU1ZQjQ/view?usp=sharing

We have analysed everything, from checking and switching sensors, boost sensors, temperature sensors, switching the compressor, clean and trace all electrical cables for injectors to ECU, grounding, replacing air and fuel filters, inspecting turbo (compressor vane turns freely), and even had 2 injectors replaced since there was a little diesel leakage for the port engine. No diesel or water contamination on the engine oil nor have we ever had to refill the oil. In other words we do not think there is any piston or ring problems as no smoke during normal operation and does not consume any. Props, hubs has been checked and switched, so no problems there.

Do let me know your thoughts as we are baffled by this and although it is not a MAJOR issue, it would just be more satisfying to get that little hick up out of the way.

Thank you and good day!
Christopher

 

[Portofino]

Tnx for the comprehensive signs symptoms and treatments done thus far .
It will be the turbo .
There will be a larger gap between the vane tips on the port engine .
The tips burn out with excessive exhaust gas temp .
On a recent post by MapishM "EGT guages (MAN)" etc etc there's a link on his initial post explaining all .


Here's some more background 1st para for you .

We've already mentioned that excessive EGT can cause engine damage or turbocharger damage, but let's get more specific. Which parts will fail first is a matter of the design and materials used in the various parts of the turbo-diesel, but usually it starts with the turbocharger. Under sustained excessive EGT, the square corners at the outer ends of the vanes, where the material is thinnest on the turbine wheel, can become incandescent and then melt, resulting in a rounding off of the square corners.


If you or your mechanic finds this indication before anything more serious happens, consider yourself very lucky, because shortly after the tips melt, the turbine wheel goes out of balance and wipes out the turbocharger bearings, which may or may not result in shaft failure and destruction of the turbine and compressor wheels. Excessive EGT can also erode or crack the turbine housing. In extreme cases, high EGT can drive the turbocharger into an overspeed condition that exceeds the designed operating speed due to the additional heat energy. When this happens, either the turbine wheel or the compressor wheel may burst. If the turbo doesn't go first, excessive EGT, if sustained, will damage the pistons. Such damage can include piston deformation, melting, burning, holes, cracking, etc. This damage is cumulative, so if you slightly burn a piston top, the engine may continue to run without problems, but the next time you run excessive EGT more damage may be done, and so on, until failure occurs. Piston failure can be catastrophic -- that means very expensive. At a minimum, an engine overhaul will be required, and that too is expensive. Excessive EGT can also cause exhaust manifold and cylinder head cracking. Exhaust valves can fail from high EGT as well. Among the first engine parts to suffer damage will be those made of aluminum since aluminum has a lower softening and melting temperature than steel or cast iron. Diesel pistons are aluminum, and a growing number of diesels also use aluminum cylinder heads.

 

[scubaman]

I'm certainly no expert on this, but wouldn't burnt out turbine vane tips show in lower boost pressure across the rev range. For the most part, the boost pressure seems to match that of the stb engine when on equal revs. If anything, the port engine seems to produce a slightly higher pressure.

Don't know how the boost pressure is controlled on these engines (no wastegate?) but seems as if it is lost somewhere when the turbo takes over.

 

[[2068]]

Could be a bearing problem with the turbo, preventing it from spooling up at low airflow rates.
Have you checked for play in the shaft?

 

[Portofino]

Boost P on the port engine looks to me all over the place eg 2150 rpm it's 80 while the Stb is 170 ,
Soon later it stalls back to 90 while Stb carries on to 190 +

What we need to know is bit more about "prop hygiene "
Duo props are v susceptible to even 0.001 mm of growth ,well even the slightest knocks rpm off = excess load .
Also a pair of 350 hp in a 40 ftr albeit a narrow by today's standard 3.55 M feels to me on the edge of power /weight ratio .
Toss in some fouling a fews years of weight gain and there you have it .

It starts intermittently on the most fouled of the pair ,the one with the dirtiest props , run as hard as the one with cleaner props .If only he could have seen the EGT,s difference
At first it's masked by the good one pulling it up .

It's amazing what a difference fouled props make to EGT .
Not to be confused by WOT or speed .
Eg after a lay up of say only one month in the summer Med ,I can only or more correctly elect to go 24-25 knots
Because the EGT,s shoot up over 600 /650 ,and load mid 90 ,s %
The boat will go faster ,plenty of torque ,but I don,t .

A snorkel 20 mins /prop /rudder later ( leave the hull ) Ok water temp is 24-26 degrees in the SoF
EGT of 600 now is 35 knots that 10 more now for the same temps
27 knots 560 ish load 82 % ---- engines and boat loving it --so am I btw

Point is VP say 10% or so off WOT but that's all ball park on a dry stacked new boat ,not a real world case with what ever fouling a real boat gets .
So the owners enter the EGT danger zone time n time agian ,

 

[kashurst]

assuming the boost pressure sensor is working, I think you have a tired turbo.
Looking in the end of the turbo doesn't really tell you the whole story, you have to take them apart to see how much clearance there is.

 

[Portofino]

Could be a bearing problem with the turbo, preventing it from spooling up at low airflow rates.
Have you checked for play in the shaft?

Yup the burn,t tip syndrome leads to imbalance with excessive temps in the oil journal ( assume its oil pressure lubed )
Bearing follow closely 2nd as explained in my post # 2 .
Starts to wobble about , air gap now widens at one side and closes at the Opersite side of the circle ,boost P rises n falls off - which is what the Op reports and I see on the helpfull vid .

 

[julians]

portofino, - you do know that even though the volvo engines dont have EGT guages, they do have egt sensors, and the electronics throw a warning and automatically lower the engine speed if they detect too high temperatures.

edited to add : actually the newer EVC versions do have EGT data in the digital display, its just the older version that only has the warning and automatic limiting of performance.

 

[Portofino]

portofino, - you do know that even though the volvo engines dont have EGT guages, they do have egt sensors, and the electronics throw a warning and automatically lower the engine speed if they detect too high temperatures.

edited to add : actually the newer EVC versions do have EGT data in the digital display, its just the older version that only has the warning and automatic limiting of performance.

No I did not know that .
Is there a "sensor error " function whereby it's tells you a sensor gone down ?
Do you know where they are -up stream or down stream of the turbo ?

Either way it's got all the classic worn turbo symptoms .But then after 10 y or so I guess most bolt on,s are on borrowed time ,just nice to make that 15-20 y if you can .

 

[[2068]]

Yup the burn,t tip syndrome leads to imbalance with excessive temps in the oil journal ( assume its oil pressure lubed )
Bearing follow closely 2nd as explained in my post # 2 .
Starts to wobble about , air gap now widens at one side and closes at the Opersite side of the circle ,boost P rises n falls off - which is what the Op reports and I see on the helpfull vid .

Yes, there is an oil feed that goes in to the top of the bearing, and a return line underneath.

 

[aquatom]

Never seen a worn turbo on a D6 yet. Have had exactly the same symptoms on one before which turned out to be a broken valve seat (I can't remember if it was inlet or exhaust). Everything worked fine with supercharger in then revs dropped off when supercharger cut out. When it would get to max revs it was a couple of hundred revs down from the other engine.
It showed up on a compression test with the vodia.

 

[volvopaul]

I also had a D4 loose power top end , turned out to be the dealer had intercooler off and had forgot to fit rubber pipe between turbo and intercooler clip tight enough .
Remember in the cycle of the supercharger is ECU attained to give boost where the turbo has to rely on its own revs to give boost .

I think you may have been chasing around and spending unnecessary, the vodia test would show and cylinder imbalance ( often described as a compression test)

 

[Lax207]

Tnx for the comprehensive signs symptoms and treatments done thus far .
It will be the turbo .
There will be a larger gap between the vane tips on the port engine .
The tips burn out with excessive exhaust gas temp .
On a recent post by MapishM "EGT guages (MAN)" etc etc there's a link on his initial post explaining all .


Here's some more background 1st para for you .

We've already mentioned that excessive EGT can cause engine damage or turbocharger damage, but let's get more specific. Which parts will fail first is a matter of the design and materials used in the various parts of the turbo-diesel, but usually it starts with the turbocharger. Under sustained excessive EGT, the square corners at the outer ends of the vanes, where the material is thinnest on the turbine wheel, can become incandescent and then melt, resulting in a rounding off of the square corners.


If you or your mechanic finds this indication before anything more serious happens, consider yourself very lucky, because shortly after the tips melt, the turbine wheel goes out of balance and wipes out the turbocharger bearings, which may or may not result in shaft failure and destruction of the turbine and compressor wheels. Excessive EGT can also erode or crack the turbine housing. In extreme cases, high EGT can drive the turbocharger into an overspeed condition that exceeds the designed operating speed due to the additional heat energy. When this happens, either the turbine wheel or the compressor wheel may burst. If the turbo doesn't go first, excessive EGT, if sustained, will damage the pistons. Such damage can include piston deformation, melting, burning, holes, cracking, etc. This damage is cumulative, so if you slightly burn a piston top, the engine may continue to run without problems, but the next time you run excessive EGT more damage may be done, and so on, until failure occurs. Piston failure can be catastrophic -- that means very expensive. At a minimum, an engine overhaul will be required, and that too is expensive. Excessive EGT can also cause exhaust manifold and cylinder head cracking. Exhaust valves can fail from high EGT as well. Among the first engine parts to suffer damage will be those made of aluminum since aluminum has a lower softening and melting temperature than steel or cast iron. Diesel pistons are aluminum, and a growing number of diesels also use aluminum cylinder heads.

Hi portofino, thanks for the input. Yes we have visually checked the turbo from the exhaust side and the compressor blade seems to rotate freely. There is no resistance or so with that.However we were keeping the turbo as a last option to open up. And from what it seems I guess it would be a good idea to open them apart and perhaps do some cleaning if required. Especially now that you mentioned about the worn out tips, it would be a good place to start.
I am also not sure whether or not this engine uses variable vanes or fixed vanes. Cant seem to find the detailed specification on them.

 

[Lax207]

I'm certainly no expert on this, but wouldn't burnt out turbine vane tips show in lower boost pressure across the rev range. For the most part, the boost pressure seems to match that of the stb engine when on equal revs. If anything, the port engine seems to produce a slightly higher pressure.

Don't know how the boost pressure is controlled on these engines (no wastegate?) but seems as if it is lost somewhere when the turbo takes over.

I do not think there is a wastegate, but as portofino mentioned if too high egt or worn out blades could create the excessive pressure?

 

[Lax207]

Could be a bearing problem with the turbo, preventing it from spooling up at low airflow rates.
Have you checked for play in the shaft?

Yes we have checked, there is no play or resistance on the shaft so far. But we have not taken apart the turbo totally as we just did check from the exhaust side.

 

[Lax207]

Boost P on the port engine looks to me all over the place eg 2150 rpm it's 80 while the Stb is 170 ,
Soon later it stalls back to 90 while Stb carries on to 190 +

What we need to know is bit more about "prop hygiene "
Duo props are v susceptible to even 0.001 mm of growth ,well even the slightest knocks rpm off = excess load .
Also a pair of 350 hp in a 40 ftr albeit a narrow by today's standard 3.55 M feels to me on the edge of power /weight ratio .
Toss in some fouling a fews years of weight gain and there you have it .

It starts intermittently on the most fouled of the pair ,the one with the dirtiest props , run as hard as the one with cleaner props .If only he could have seen the EGT,s difference
At first it's masked by the good one pulling it up .

It's amazing what a difference fouled props make to EGT .
Not to be confused by WOT or speed .
Eg after a lay up of say only one month in the summer Med ,I can only or more correctly elect to go 24-25 knots
Because the EGT,s shoot up over 600 /650 ,and load mid 90 ,s %
The boat will go faster ,plenty of torque ,but I don,t .

A snorkel 20 mins /prop /rudder later ( leave the hull ) Ok water temp is 24-26 degrees in the SoF
EGT of 600 now is 35 knots that 10 more now for the same temps
27 knots 560 ish load 82 % ---- engines and boat loving it --so am I btw

Point is VP say 10% or so off WOT but that's all ball park on a dry stacked new boat ,not a real world case with what ever fouling a real boat gets .
So the owners enter the EGT danger zone time n time agian ,

Hygiene wise, props have been checked and switched with stbd. No growth whatsoever on them also with hull. We use Hempel anti fouling and so far it has been terrific. From all indications it seems we will go ahead and check up the turbo as mentioned. Cant really think of anything else so far

 

[Lax207]

Never seen a worn turbo on a D6 yet. Have had exactly the same symptoms on one before which turned out to be a broken valve seat (I can't remember if it was inlet or exhaust). Everything worked fine with supercharger in then revs dropped off when supercharger cut out. When it would get to max revs it was a couple of hundred revs down from the other engine.
It showed up on a compression test with the vodia.

Do you know where exactly this valve seat is located? Would you have a copy or remember what else the Vodia test can give? Although may not be very useful in this case as the dealer said, I would still like to have a test check to make sure all parameters are good for our own satisfaction.

 

[Lax207]

Do you know where exactly this valve seat is located? Would you have a copy or remember what else the Vodia test can give? Although may not be very useful in this case as the dealer said, I would still like to have a test check to make sure all parameters are good for our own satisfaction.

Ahhh I misunderstood, I thought there was some special valves on the exhaust but yes of course you mean on the cylinder head. Ok, I think we will do a Vodia check too, who knows what results we would get.

Thanks!

 

[QBhoy]

All of the above....not too familiar with these modern engines, but is there an actuator that's sticking on the turbo ?
Obviously she isn't getting enough boost to satisfy the fuel provided. Answer will be somewhere stated above, but likely expensive, unless a simple sticking actuator.
I'd be tempted to remove the air intake ducting and check the turbo for bearing play. Also look for excess signs of oil whilst you are in there.

 

[QBhoy]

Perhaps even simpler....whilst running, check for exhaust gas leaking before it gets to the turbo. Use a piece of A4 white paper and hold it against the exhaust piping and joints...particularity the flange before the turbo. An old fashioned but useful indication.