turbo owners: caution in transport

[Berniep]

Since it can't (as far as I know no engine has both the intake and exhaust valves open on the same chamber at any given time)

Regular 4 stroke engines can have both intake and exhaust partly open at the same time.
Fourth paragraph down in this page:
Timing Tutorial
I don't know anything about diesel valve timing but with the physics involved it could be similar.

 

[Wayne County Hose]

Very interesting topic. I would like to see a definate result.

Engines do have intake and exhaust valves open at the same time. Moreso in a race engine. It is called the scavenging effect. When the piston comes up to push out the exhaust gases, the gases move like a slug down the pipe. As the piston gets closer to top dead center, it slows down. The slug is now moving faster than the piston. The camshaft now opens the intake valve. The slug of exhaust moving down the pipe actually pulls the intake charge into the cylinder. In camshaft terms, this is called overlap. The more overlap, the more scavenging, the more horsepower. On a low RPM diesel, I don't think there is much overlap. But, I have not studied diesel engines either, this is just speculation.

Now, if this were possible, picture the air being sucked thru the intake, thru the cylinder, thru the exhaust and past the turbo, making it spin. The spinning turbo now injects an air charge into the intake. When a turbo spins, it increases intake pressure. We all no there is no such thing as a perpetual motor, but the turbo would actually help to spin itself. But, turbos are very inefficient at low rpm's (flow).

Interesting, to say the least.

 

[Doc_Bob]

Both the K salesman & the service dept cautioned me (from experience) that when transporting a tractor w/a turbo, be sure to plug the exhaust in transit. Apparently when moving (with engine obviously off) a vacuum is created in the exhaust pipe thereby spinning the turbo w/o lube. dusts the turbo bearings. they had 3 units go down before cluing on this. Just a heads up as turbos are more frequent now, and owners haul their own bb

Same thing is mentioned in the NH owners manual for my Turbocharged TN70A. Keep your turbo exhaust plugged when moving.
Bob

 

[2Botas]

Diesel engines have valve overlap as well. And i do believe that if givin the right circumstances (engine has one cylinder that happens to have both valves open at the same time, and the exhaust is in such a position that a pressure or a vacuum is created) you could get some pinwheeling. But, it would take one heck of a long ride to damage the bearings. Mostly because a turbocharger is nothing like a pinwheel. A turbo does not spin simply because air is moving through it. A turbocharger spins because the exhaust gases that are moving through it are expanding rapidly. Its the rapid expansion, not the air flow. This is why the leaf blower didnt spin the impeller wheel very fast. So i cant imagine that pressure or a vacuum in the exhaust in transit would cause it to spin more than 1 or 2 rpm, if at all. But i think this myth is plausable. The mythbusters really should look into this

As for the "dumping water in the intake to remove carbon" trick- That actually does work. But, it is a very stupid way to do it. The reason it works is because the water displaces air in the cylinder which raises the compression ratio drastically. and it causes a extreme lean condition.It basically creates so much pressure and heat in the cylinder that it breaks up the carbon. Its also a great way to bend a connecting rod

 

[Smokin Diesel]

They'll turn faster than you think with a little airflow. And it doesn't take much spinning to do damage to the center bearing of a turbo. That "bearing" is basically a bronze bushing. The pressurized oil from the engine will suspend the center shaft of the turbo inside the bearing with the engine running. Without the oil flow, the steel shaft is riding directly on the bronze bushing. It won't take much rotaion to wallow out the bushing. Then when the engine is started, the oil won't make a complete path around the bushing, steel continues to hit and wear away the bronze, and eventually the compressor hits the housing.

It only takes a little wear to start a rapid turbo failiure.

 

[slowzuki]

Won't happen though. Think of a windy day, open your kitchen window, now run down to the basement and see if your furnace fan is turning over. Bettcha it won't be.

Maybe just maybe you might get a tiny bit of movement with a 6" straight stack on a puller tractor. Thats a huge maybe.

Covering the stack is still a good idea because dirt and water can get in there when hauling on the road and they can damage the turbo or even get into the exhaust valves/cylinder on turbo/non-turbo machines.

 

[big bubba]

thanks for all the input in this discussion, an example of the forum medium at it's best holding opposing viewpoints. but we need to move from the empirical and physics observations to reality and experience. who has actually experienced this phenomenon? maybe someone should post the question on some kind of diesel truckers forum.....in the meanwhile, I'll be sure the driver covers the stack of my brand new M8540 turbo as he delivers it to my farm tomorrow. and let the skeptics continue to ridicule.....or should I invite you all to a tractor pull at my place and settle it that way bb

 

[2Botas]

Won't happen though. Think of a windy day, open your kitchen window, now run down to the basement and see if your furnace fan is turning over. Bettcha it won't be.

Thats not really a good example. The fan on a forced air heating system rarely ever uses outside air. It recirculates inside air, so obviously a open window will not move air through that system.

A good example would be this- Say the wind is blowing from the north and you open a window on the north side of your house. You then walk down the hall and around the corner to a bedroom on the south wall of the house. You open a window in the south bedroom and place a fan in it, but leave the fan off. You then leave the bedroom and hall doors partially open and observe your fan.....Its turning. I just did this test for fun, I had to use some heavy door stops to keep the doors opened just a little bit. But the fan was most definatly spinning.

Nonetheless, Neither of these home examples are applicable to the question at hand.

 

[slowzuki]

They are applicable because we are trying to show the difference between pressure and flow, and the difference between a flow with a direction to it vs turbulence.

Normal diesel have no overlap in their valve timing, there dead ending the tube.

A dead ended tube can have a harmonic lenght such that air moving over the end can set up standing waves of air moving back and forth, like a pipe organ sort of. But, the mass of the impeller would require much higher forces than a standing wave could exert.

The tube can also have turbulent (random) mixing propagate down from the opening but any one direction of the air movement is very brief and weakens dramatically as you go down the tube.

For better examples I offer the following:

Drive in your car at highway speed, crank your window down a bit, many cars will have a natural frequency at some point that buffets and will sort of pound your ears. The frequency of this depends on a few things but basically becomes higher pitch with smaller volumes connected to the opening. Notice at this point not much air flow is occuring in the car.

Open the window more, all the way even, despite no long tube connecting the window to your cars interior, and venting in the car design which actually allows positive airflow into the car to a degree, a fan would have to positioned carefully to have the wind turn the blades.

As you made that shape narrower and longer, the wind would affect less and less area of the car interior, so for example, drivers window of a stretch limo is open, the ladies silk dress in the back seat may not even flutter.

So again, back to my house example, open a (one) window, a fan on the other side of the house or any type will not operate.

 

[slowzuki]

That would only be a good example if we were talking about a jet turbine engine pointed into the wind.

A good example would be this- Say the wind is blowing from the north and you open a window on the north side of your house. You then walk down the hall and around the corner to a bedroom on the south wall of the house. You open a window in the south bedroom and place a fan in it, but leave the fan off.