Old wives tale? General turbo question....

[chrisk1500]

Hey Guys,

This is not really 6.5 related at all (unless your ride has stacks and you need to tow it), but it is about a diesel turbo and I know there are a few guys on here that might be able to answer it.

I bought a combine the other day as harvest is quickly approaching and I needed to have it hauled from the sale site to my yard (150 miles). We got the combine loaded up and the hauler asked me to go tape up the end of the stack (the stack would be facing directly into the wind).

I asked him why. Was he afraid of birds flying into the system? He answered that he was once told about a guy who had his piece of equipment hauled and did not tape up the exhaust system - the force of the air ramming down the muffler kept the turbo spinning for the whole trip - without an oil supply to the turbo, it got toasted.

Is it possible? I can see what he was saying, but I had never heard of it before (and never taped up and of the equipment we own that has stacks on it)....better safe than sorry I suppose.....

 

[Mad Maxx]

Yea, I'd say it's a possibility. Not likley, but possible.

 

[Missy Good Wench]

For the turbo to spin the air being forced into the system would have to be able to go somewhere.

The turbo is designed to spin from very hot high velocity exhaust being fed through the turbine wheel.
Backfeeding it is just not gonna do anything as there is no place for the iar to go plus the fact that the air is flowing the wrong direction to make the wheel turn.

Now all theory aside.
A roll of duct tape is cheap and it takes only a few seconds to tape the stack shut.

Tape it up and then you wont need to worry about it eh ??

 

[Joey D]

I have read the same thing. I also have seen countless pieces of equipment being hauled down the highway with nothing covering the exhaust.

 

[Michaeljp86]

I think is BS myself, if the exhasut manifold was removed I suppose it could happen. The only way I could see it doing that is the air would have to go down the exhaust through the turbo, through the engine and out the air intake. Seem highly unlikely to me. Stick your mouth on your lawn mower mufler and see if you can blow through the carb.

 

[JiFaire]

Now all theory aside.
A roll of duct tape is cheap and it takes only a few seconds to tape the stack shut.

Tape it up and then you wont need to worry about it eh ??

x2... :iagree:

 

[635]

In all of the years I hauled heavy equipment, from the factories to the dealers, the last thing we did was to tape up the exhaust pipe. This was common practice for everyone hauling anything with a turbo. Cat, Case, International, and many others all demanded the exhaust pipe be covered. This was to keep the turbo from spinning because of no oil!

 

[gmctd]

Old wives indeed, and always seems to be a few here, MGW excluded - turbo's spinning, my ankle - it is to prevent rain from entering the exhaust stack - never know when the equip will be parked outside in a sudden deluge, or over-nite, or over a weekend, or Holiday - common sense, dudes: if ya got it, use it........................

 

[chrisk1500]

I told him the same thing....he replied that all it takes is for one intake and exhaust valve to be open just a fraction for the damage to take place...a long shot I suppose, but not a chance I was willing to take....

I taped it up and and got it home....

I can see it keeping the rain or stray bugs out of the system....

BTW - machine was an IH 1460 axial flow for those of you who have hauled them before...

 

[Dan Hunter]

I wonder what TD thinks.

The aircraft I train on no longer allows the crew chief to hand rotate the prop the turbine engine to clear the intake air temp to a level the computer will tolerate for an automated start for the same reason...oil supply issues.

 

[Michaeljp86]

Old wives indeed, and always seems to be a few here, MGW excluded - turbo's spinning, my ankle - it is to prevent rain from entering the exhaust stack - never know when the equip will be parked outside in a sudden deluge, or over-nite, or over a weekend, or Holiday - common sense, dudes: if ya got it, use it........................

Thats what I think, Ive seen lots of combines and tractors loaded on a lowboy where they sit at a angle, like they the remove the front wheels of a combine. The angled stack almost has the opening straight up.

Theres some big farmers near me who had a big JD dozer. The exhaust came up along the roll cage at a angle with a turndown on it that was upside down, it was like a funnel for the rain.

I told him the same thing....he replied that all it takes is for one intake and exhaust valve to be open just a fraction for the damage to take place...a long shot I suppose, but not a chance I was willing to take....

It would have to be one intake valve and one exhaust valve in the same cylinder.


Maybe it could happen on a 2 stroke? I dont know much about those.

 

[Turbine Doc]

Old wives indeed, and always seems to be a few here, MGW excluded - turbo's spinning, my ankle - it is to prevent rain from entering the exhaust stack - never know when the equip will be parked outside in a sudden deluge, or over-nite, or over a weekend, or Holiday - common sense, dudes: if ya got it, use it........................

X2 :thumbsup: same issue we have on incorrectly stored locomotives water fills the exhaust, then fills the turbo, then flows in to open valves, on top of pistons, (16) opportunities that one of them is lined up correctly to allow water in, and since water doesn't compress well, you wind up with bent rods and expensive repairs last one it happned to here; we lost (3) PAs (power assemblies)

Same reason they have a device called a "rain cap" you know that "flapper valve" you find on many tractor exhaust pipes, I back that up with a coffee can on my JD-2020 and Ford 535 tractors flapper covered with coffee can

In order for the turbo to "windmill" it would take a significant volume of air to make it happen IMO, the air would have to make it thru the stack, and thru the muffler/resonator portion of the stack to windmill the turbo, then the journal bearings & seals friction would have to be overcome, remember shaft rides on oil film not the bearing so much, so if turbo shaft is resting on the journal & seals gonna take some volume of air to spin it.

Now jet engines where the shafts rest on precision ball and roller bearings can windmill with breeze through the engine if in sufficient quantity, though most aircraft turbines to have a "windmilling" duty cycle, ususally on magnitude of days they can windmill with no power on the engine, but they use synthetic oil and if the engine is turning the lube & scavenge pump is also pumping as it is mechanically coupled to the turbine's rotor shaft.

Maj. Dan I don't understand the logic behind the no prop turn, I'd be interested in seeing more on that myself to understand it, doesn't make sense it would be a no oil issue, could be something unique to that particular mfr, I was intimate with Allison 501's and GE turbines, about 28 years on those kind or another; are we talking about one of those turbines or another flavor.

We used to have a duty limit on ours like 14 minutes with no power turbine rotation with the core still turning, that wasn't for oil issues it was for blade & vane limits, the sump cavity temperature for that bearing should be the criteria for a spin/no spin situation, if no oil/ is the issue, has the mfr got data that shows it's bearings "make metal" with just hand rotation, should be a caged ball or roller bearing there, those are pretty robust bearings.

Think about it, in multi engined aircraft if you have an inflight shut down the engine is windmilled all way home, most time if the shutdown wasn't engine caused it survives without damage, even with a sheared/damaqged inlet/transfer gear box, radial, or horizontal drive shaft not transferring power to the accessory drive for the on engine fuel & lube pumps.

 

[Dan Hunter]

During the two week strike, they placed absorbing crystals in 1 lb. bags...bags of four in the intakes and then covered them.

 

[Detroit Dan]

I drove heavy wrecker for a few years and this topic came up once in a while Some shops insisted we cover the stack if we were towing it backwards. So we carried a couple cut up milk jugs with bungee cords to throw on them quick. But it was just to keep them happy, because for the most part everyone believed it to be an old wives tale. We surveyed a lot of diesel engine techs who pretty much laughed it off. Nobody seemed to fear that our wrecker was going to achieve a speed that could get the turbo turning, they operate at how many thousands of rpms? I know it's many times faster than engine speed, 65 mph is not going to accumulate enough air volume. if the fan was just turning slightly from the breeze, it wouldn't hurt anything for a few hours of rolling along making no heat. And again, if that air doesn't have any easier path to exit, it isn't going in. I personally towed a lot of road tractors backwards all over New England and never heard about a turbo failing.
I wouldn't say it is necessarily for the rain, when shops wanted it done it was because of the spinning turbo concern. Obviously driving any distance in a downpour would let water in, but I don't know that I'd worry about it with just a little regular rain. I think it would take a tremendous distance driven to accumulate enough water to harm anything.
This is a really cool topic though, I enjoy reading everyones opinions on this.

 

[Michaeljp86]

Obviously driving any distance in a downpour would let water in, but I don't know that I'd worry about it with just a little regular rain. I think it would take a tremendous distance driven to accumulate enough water to harm anything.
This is a really cool topic though, I enjoy reading everyones opinions on this.

On farm and construction equipment it could, there may be less then 3ft of exhaust pipe there and could come straight down ontop of the engine. No long pipe going down like on a semi truck.

 

[Michaeljp86]

Why doesnt someone call myth busters?


Take the air cleaner off your engine and take a air compressor and blow through the exhaust and see if the turbo spins.

 

[Turbine Doc]

To be valid test would have to be same flow of air across top of a stack at say 65 mph, pressure of a shop air compressor would pressurize the exhaust to same psi as the compresor and that would possibly spin the turbo.

One of you guys with stacks, how about trying this, air filter off, and leaf blower maybe what 100 mph of wind from one of those, blown across the top of your stack and see if the turbo spins from something like that, if it spins then need to figure out how to stand far enough away from the exhaust tip to replicate 65 mph of wind across top of the stack and check again.

 

[Dan Hunter]

Maj. Dan I don't understand the logic behind the no prop turn, I'd be interested in seeing more on that myself to understand it, doesn't make sense it would be a no oil issue, could be something unique to that particular mfr, I was intimate with Allison 501's and GE turbines, about 28 years on those kind or another; are we talking about one of those turbines or another flavor.

So good to hear from you. I don't understand it either but then the reduction gearbox is having problems and the supplier is doing whatever they can to to mitigate the problem so...they do what they do. Personally, I'm not that impressed with low speed movement without positive oil pressure. I might be concerned about constant moderate speed movement. I'm WAY concerned about introducing moisture into an area that should otherwise respire VERY HOT, DRY air and I think that's an issue to this thread.

Again, good to hear from you.

 

[Michaeljp86]

To be valid test would have to be same flow of air across top of a stack at say 65 mph, pressure of a shop air compressor would pressurize the exhaust to same psi as the compresor and that would possibly spin the turbo.

One of you guys with stacks, how about trying this, air filter off, and leaf blower maybe what 100 mph of wind from one of those, blown across the top of your stack and see if the turbo spins from something like that, if it spins then need to figure out how to stand far enough away from the exhaust tip to replicate 65 mph of wind across top of the stack and check again.

I was thinking just point the air nozzle into the stack and blow, a leaf blower would work better. I think I have a craftsman shop vac that will blow 100mph, maybe if I have time Ill give this a try tomorrow.

 

[96GMC6.5L]

I will be interested to see the results...