Blew turbo, west of Albuquerque

[Zeroclearance]

Sean, it's good news that you got the turbo mounted and the engine running.    Who knows you might be now at 105% vs the less than 100% that you have been running lately.   BTW, how much oil did you pour in to bring it back to normal?

[luvrbus]

Sean, glad you had no internal problem .
I hope you never need it again but here are engine numbers to put in your files that will show the parts for the mounting like yours 
model 8087-7087
serial 8VF 128885 

good luck

[Sean]

Kevin -- I put a gallon in, and I look to be maybe one or two quarts low still.

Clifford -- I have the model and serial number for my engine.  Unfortunately, since Detroit sold the two-strokes to MTU, the computers that the distributors use to pull up the builds are now running on MTU's system, which still has lots of kinks.

We were able to call up the build list for my engine, but there are no exploded diagrams.  We had to go back to the printed books.  Those seem to be a bit buggy, too -- when we finally found the page with the correct blower cover, it showed the two mounting holes for the turbo, but the oil drain hole was missing from the picture.  The oil drain seal was not shown on that page or on the page for the turbo itself;  we finally found the part number on the turbo parts list, but it is just described as "seal" -- we only figured it out based on dimensions.

Since the blower cover page was missing the drain hole, and also showed a screen that doesn't exist, we kept doubting whether it was the right page, and so were unsure of the gasket number shown there,

I will be glad when MTU gets the kinks out.

-Sean
http://ourodyssey.blogspot.com

[luvrbus]

Sean, that be S & S thing and not MTU I never have a problem getting both screens the one for the the turbo an the other under the air horn from WW Williams     good luck

[Busted Knuckle]

Sean, that be S & S thing and not MTU I never have a problem getting both screens the one for the the turbo an the other under the air horn from WW Williams     good luck

Clifford what does a horn have to do with the turbo?!?!?!

Jest kidd'n but there are those who haven't got a clue as to what you mean by the air horn!

 BK  

Oh I know better, but you guys know me I never pass a chance to be witty!

[Sean]

This will be, I hope, my final update on the turbo repair.

Tonight we are at a picnic area on US-60 west of Quemado, NM, some 140 miles from where we started the day.  Aside from blowing huge quantities of blue smoke at the beginning, tapering off steadily throughout the day, and the fact that the whole coach now smells like burning oil, we have had no problems or issues.  I have tried to be fairly gentle on the turbo while we seat the bearings and seals, but, subjectively, we have normal power now, at least as normal as it gets at 6,000-7,000' altitude.

This morning, during my third and final warm-up/cool-down cycle, I plugged in the DDR to check on everything.  Specifically, I checked injector response, which looked good on all eight cylinders, ranging from 1.07 to 1.17.  I also ran the injector cut-out test on all cylinders at idle as well as 1,000 rpm, and all injectors elicited a response, with pulse width increasing by 0.2 to 0.4 for each cylinder.

For those unfamiliar, what this latter test does is to first report the amount of fuel being provided to the cylinders in the form of "pulse width" (PW), the amount of time the injectors are commanded to inject.  Then it shuts off the injectors one at a time and reports the PW as each injector is off line.  The idea here is that when a cylinder that was contributing real work gets turned off, the DDEC will have to increase the PW to supply more fuel to the rest of the cylinders to carry the load.  If you turn off one injector, and there is no resulting change in PW, that means that that cylinder was not doing any work, which could mean a bad injector (or a number of other problems).

I am interpreting the results, being fairly consistent across all cylinders, as meaning that I still have all eight injector tips, and all the exhaust valves are intact.  I'm not conversant enough with these sorts of tests to rule out any other problems (low compression, marginal injector, etc.), but I am fairly confident at this point that the turbine failure was not due to FOD originating in the engine.

While we were driving, Louise reported that the turbo sounded "rough" and that it made much more noise than the old one.  That's cause for some concern, but not too much, yet -- I still have not replaced the heavy exhaust blanket over the turbine housing, nor have I secured the hatch (which involves caulking it, screwing it down, and replacing the 1/8" vinyl flooring over the top), and both of those things would attenuate the sound considerably.  In fact, Louise later reported that the sound was lessened when she stood on the hatch.

I have been asked whether there might have been something I could monitor that would have provided early warning of this impending failure.  To be honest, I don't know.  I don't suspect I would have noticed anything unusual on an oil temperature gauge, or even exhaust pyrometers, that would have led me to check on the turbo.  Even the boost readings seemed normal right up until failure, and any changes in those sorts of readings would have been so gradual over time as to be unnoticeable -- sort of like putting a frog in cold water, and then boiling it.  That said, I sure do wish I had pyrometers.  Separate pyrometers for each manifold would have given me the confidence ahead of time that I did not have a single-cylinder failure of some sort.   Also, they might have alerted me that the exhaust was getting hot enough to melt things (turns out, the thermoplastic wires were OK -- I only melted the slit loom).

Again, I would like to thank everyone here for their help -- this board is a fantastic resource, and it is this kind of selfless outpouring of assistance that has kept me here, usually answering questions, long after my bus was completed.

-Sean
http://ourodyssey.blogspot.com

[oldmansax]

Sean,

You get back what you put in......

I think I speak for a lot of us here who have benefited from your posts over the years.

Thanks for such a complete and well written account of your trouble. While we hope no one has to go through it like you did, it will be invaluable to anyone who has a similar problem.

TOM