Not a good day for my 6-71s

Was it the exhaust turbine that came apart or the air side impeller?

Ski in NC said:

Was it the exhaust turbine that came apart or the air side impeller?

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We were told the exhaust Ski but I asked for a confirmation. Quite frankly if it was air side I'll be pissed as the engine didn't cause the issue. I'll hold my thoughts until I hear from the repair facility.
Are you thinking something?

Chunks from the turbine generally exit the engine with no harm. Just chunks in the muffler. Chunks from air side impeller go towards blower. Generally get stopped by intercooler if TI engine, right into blower on T engine.

Kinda rare for turbine to get eat up unless debris from engine hits it, but if that was the case, comp would be zero on a hole or two from missing valve parts. None is zero.

Ain't got my arms around this one yet.

I'm with you on this. I guess we'll know better when I get the report.

Perhaps the turbo is slobbering when cold, my Saviem/Mack did that, white smoke. Cleared at temperature.

djones44 said:

Perhaps the turbo is slobbering when cold, my Saviem/Mack did that, white smoke. Cleared at temperature.

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Its a Detroit, they all do that.

So here we are almost 2 months to the day from my last post on this subject. The boat has been floating since the 6th of July. The plan was to reassemble and then retest the engine. I had to leave for a week and I had my guys in there for two weeks installing my new inverter system. (which worked out great, the inverter install) The yard can't seem to find the energy to get involved to complete this thing and I'm ready to kill them. You'd think they'd want to get paid.
Some how through this they have managed to bugger my shifter cable/linkage as now the Port engine (the one with the issue) isn't moving smoothly. They of course said there was nothing wrong and just give some fuel so they can see how it runs on the way over to their marina. Having owned this boat for 14 years I know how it supposed to shift and it isn't right so it isn't going over 700 RPM on the way to the yard as we all know who pays for the damage if it's not all the way in gear.

Meanwhile they want to put the jackets on the turbo's. Well part of the reason they started this mess in first place was I had a leaky turbo connection on the exhaust side. Needless to say I won't let them put the jackets on until the engines have been run up under load to confirm no leaks.

Question to large turbo experts. If I increase RPM up to 2000 while in neutral is there enough exhaust pressure between the turbo and the elbow to check for a leak?
I'm to the point where I need to deal with these items myself and get my boat the hell out of there before i get arrested for assault (or worse).

mbevins said:

Question to large turbo experts. If I increase RPM up to 2000 while in neutral is there enough exhaust pressure between the turbo and the elbow to check for a leak?

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Turbo's generally do not develop positive pressure unless under load...Reving in neutral will not accomplish that.
My observations from years of experience with Audi gas Turbos and VW Diesel turbos with accurate boost gauges..

I can only tell you from my trucking experience, you won't get ANY boost or manifold pressure while at idle. Has to be under a pretty decent load before the turbo spins up.

Thanks guys. That's what I was thinking but I thought I'd ask.

mbevins said:

The yard can't seem to find the energy to get involved to complete this thing and I'm ready to kill them. You'd think they'd want to get paid.
I'm to the point where I need to deal with these items myself and get my boat the hell out of there before i get arrested for assault (or worse).

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I've felt this pain several times now. My last repair was supposed to take less than a week. After six weeks, I was nearly homicidal. I just don't get these guys.

mbevins said:

If I increase RPM up to 2000 while in neutral is there enough exhaust pressure between the turbo and the elbow to check for a leak?

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If "between the turbo and the elbow" you mean the turbocharger exhaust side and an elbow that connects the turbo to the downstream exhaust system, the answer is a qualified yes.

The backpressure developed in an exhaust system has a minimum level that is a product of the size of the tubing, the number and angle of the fittings, the level of water in a lift muffler if one exists, and the overall length of the system from the turbine outlet to the atmosphere. The lowest pressure is developed at idle, the highest at maximum power.

Using a generator as an example since we can easily see the difference created by load changes that occur at the same rpm, a system might have a no load backpressure of 13 or 14 inches of water column (~34mB) to a full load backpressure in the high 20 inches (~70mB) or even higher with a poorly designed system.

Even 13 or 14 inches of water is usually enough to determine if exhaust fittings are leaking.

Don't be so hard on the mechanics. They want to replace the insulation blanket because if you took the boat and ran without it and had a fire that could be shown to be the result of leaving it off, they would be liable. Let them put it on and if you want it off, you take it off so there is no doubt exactly who created what might be a hazard in your engine room.

Heron said:

Turbo's generally do not develop positive pressure unless under load...Reving in neutral will not accomplish that.
My observations from years of experience with Audi gas Turbos and VW Diesel turbos with accurate boost gauges..

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I can understand this on turbocharged car and truck engines as they would have a by-pass of some kind to get rid of unwanted boost pressure. Is a bypass or waste-gate a normal feature on turbo marine diesels?

On my Cummins with boost gauges there is no pressure until the engine is in gear and rpm up to about 1400. Out of gear no pressure no matter the rpm.

Shoalwaters said:

I can understand this on turbocharged car and truck engines as they would have a by-pass of some kind to get rid of unwanted boost pressure. Is a bypass or waste-gate a normal feature on turbo marine diesels?

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A Bypass (either a diverter valve or blow off valve) is in a car system to de-pressurize the inlet system when the throttle plate slams shut as in a shift to a higher gear.. Without it you'd have a high build up of pressure in the inlet tract that could stall the turbo. Not good for performance (or turbo's). No need in a marine application as there is no rapid change in throttling in high torque ranges, and most are very low pressure systems..A few PSI maybe, where cars I've owned have approached 25PSI

timjet said:

On my Cummins with boost gauges there is no pressure until the engine is in gear and rpm up to about 1400. Out of gear no pressure no matter the rpm.

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Do your boost gauges give accurate load readings? Thinking of using them instead of Fuel flow meters.

timjet said:

On my Cummins with boost gauges there is no pressure until the engine is in gear and rpm up to about 1400. Out of gear no pressure no matter the rpm.

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No boost because it is unnecessary to achieve RPM you select. More load requires more fuel and therefore creates more exhaust and boost.. Diesels are fuel limited engines not air limited.

Heron said:

No need in a marine application as there is no rapid change in throttling in high torque ranges, and most are very low pressure systems..A few PSI maybe, where cars I've owned have approached 25PSI

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That reads as if you have never heard the turbo on a large marine diesel "bark."

They most certainly do experience compressor stall and the charge air pressure on a marine diesel can exceed 45 psig. That is why rapid power changes are not recommended because the pressure differential across the compressor will lead a a stall and can damage the turbo and inlet ducting.

All of this is of course irrelevant since the OP asked if he could find an exhaust leak by running the engine at high idle. He didn't ask if he could find a charge air leak.

Maybe you said already and I missed it but am curious...what year are the engines and are they TI or TA turbos ? I think TA was available after about 1988 or so. I guessing from the heat blankets they are TI ? If so has the boat ever lived in salt water ?

On the turbo 6-71 the air charge is being cooled between the turbocharger and the blower, thus all are intercooled (TI).

rardoin said:

On the turbo 6-71 the air charge is being cooled between the turbocharger and the blower, thus all are intercooled (TI).

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I asked as I was seriously interested in an older Hatteras that had 8v92TI's in FL and one engine surveyor told me he was now refusing to survey the TI engines as the salt water can corrode things to the point the salt gets into the engines. Might survey great one day and engine ruined a week later and the buyer comes complaining to surveyor about not catching the issue.

At least on the TA versions the salt water is cooling fresh water so not as risky to core engine components. Having said that, if OP's boat always in fresh water not likely the issue.

Caladan said:

At least on the TA versions the salt water is cooling fresh water so not as risky to core engine components. Having said that, if OP's boat always in fresh water not likely the issue.

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It's a TI with a closed cooling system. The boat is a fresh water as well. But this has no bearing on my query.