O/T Turbo Chargers

When hauling equipment with turbo chargers can any one say that the turbo actually turns from the air going around the exhaust pipe. I know owner manuals will say to tape up the exhaust stack to save the turbos. This is supposed to keep them from spinning when there is no oil pressure.

I have hauled equipment for years with out covering the exhaust pipe and have had no ill rusults.

For air to turn the turbo there must be air flow thru the exhaust system. For this to happen it must go in the intake and thru the engine and out the exhaust system. This cannot physically happen unless the engine is running. Because no air can flow freely thru the intake and exhaust simultaneously , because no two valves are open at the same time on any one cylinder.

For air to flow freely thru any one cylinder both valves would have to be open at the same time.

Granted that both valves are open a minute amount during overlap but for an engine to stop at this very TDC is very unlikely.

If that were true then one would have to go out an cover the exhaust on windy days. personally I wouldn't worry about it as i never see any stacks covered except for the flapper covers.

Walt

I've heard of that before but don't know if it's a real concern. I wouldn't think you get enough of a concentrated blast of air in the exhaust pipe and then through the muffler to turn the turbo. If it was a problem, I think the OEM's would want to save on warrantee work for blown turbo's by telling owners to block the exhaust pipe or have it turned backwards when transporting. Dave

I beleive you'll find that they do, very clearly, tell you to cover the exhaust during transport.
I will either cover them, face the exhaust to the rear or leave the engine running on a short haul.

Rod

Around here the dealers seem unwilling to take chances. Almost always, you see the exhausts covered, the flappers strapped down, or the exhaust covered with a garbage bag taped in place.

If damage is even remotely possible, that sure is a lot easier/cheaper than replacing a turbo or even worse, should a failed turbo come apart.

What you are saying is a lot like saying "I eat peanut butter, but haven't died. (YET!)

Cover the exhaust while transporting, cheap insurance for a very expensive item.
Guido.

It helps keep the hauler from getting sued for a new turbo when one goes out within a few days of hauling the tractor. Does it help the turbo? Who knows, but it saves a lot of billable hours with the attorney.

That subject came up on another site, the arguement got me on a "google" search of every turbo builder/rebuilder I could find. On the sites troubleshoot /failure analysis pages, not one listed air windmilling the turbo during transport as a failure cause.
Almost all listed keeping road trash,(water, dirt, rocks, metal bits) out of the exhaust / turbo / engine as a reason for covering the exhaust during transport.

I once saw a turbo off a late model IH tractor, where the mechanic had left a 3/8 x 1 bolt in the turbo intake pipe. They started it and the bolt was sucked into the turbo's compressor turbine. They did an emergency shut down, but the bolt had already nearly milled the blades off the compressor turbine, ruining the turbo and filling the engine with metal shavings.

A lot depends on the configuration of the exhaust pipe (side or rear facing exhaust area or even just a vertical stack) and the engine. If a lot of cases, the pressure at the exhaust pipe is slightly less that the pressure at the air intake of the engine. That differential in pressure can drive the flow.

If at least one of the cylinders has an open intake and exhaust valve then flow will go through the air intake through the compressor, into the cylinder with open intake, out the exhaust spin the turbine and exit the exhaust pipe. Since most of these turbo's don't have their own oil supply and pump, they dry windmill and the bearings can be damageddue to running without oil.

The big IF is: does the engine have a position where an intake and exhast valve are open on the same cylinder? If it doesn't then I'd say no problemo!

This sounds like a job for.....MYTHBUSTERS!

We always plug or cover the turboed tractors while in transport to shows or pulling events even if the trip is only a few miles. Seeing one turbo that was spun dry and big money repairs convinced me that a little effort was more than worth it.

There is a point in the 4 stroke cycle where both valves are open. Near the top of the exhaust stroke, the intake valve will begin to open and the exhaust valve will start to close. Both valves are open for a few degrees of crankshaft rotation. This is called valve overlap. To let air through, at least one piston would have to be in this position.

there's probably a little residual oil in the bearing and the turbo is cool. if the exhaust was pointing ahead making a ram air effect the turbo might wind up to a small percentage of it's operating speed. if the pipe is straight up the vacuum from the air rushung over it might make it turn a few revolutions.

the idea of junk getting in there sounds valid. just idle rambling thoughts.

we pulled eight combines with straight pipes many thousands of miles down the road without covering exhausts. when the combines were retired the lowest houred one had a twitch over 5000, yes,5000, and we only replaced one turbo on a dusted engine. jim

At the last John Deere dealer I worked at, we had several new turbo Deeres get delivered with bad turbos and Deere Co. said it was caused by the trucking with the stacks facing the wind.

Can't say I did a controlled scientific experiment on it, but that's what Deere Co. came up with. We always covered vertical stacks when trucking.

As far as what you say with it not being possible? You lost me with your reasoning. Take a turbo four cylinder engine. One common exhaust outlet attached to all four cylinders. Some can have both intake and exhaust valves open a bit. Might even be some exhaust or intake connection leaks somewhere. With the turbo bearings dry with no oil pressure or lube, and the tractor on a cross-country trip? They are just sleeve bearings with a steel ring seal and not tolerant to any dry running. I don't find it hard to believe even a slow turning turbo running dry for several days of high-speed driving might get damaged. I know for sure we took delivery of some bad ones and the trucking contractor had to pay for it.

I kind of wonder why it's even worth worrying about? Doesn't take much to cover the exhaust and play it safe.

Sounds like a myth to me. In all the years I have worked with turbo engines I have never seen a problem. I have had them come in with no exhaust stack and the shipping cover blown off the turbo. Never had a problem.Besides it would take alot of air to get past the baffles in the muffler to spin the turbo up to speed.

Why would it have to be up to speed? With nothing but sleeve bearings I can see where even a dry turbo turning very slow could get damaged over time.

You haven't had any ill results. How about the people/companies you hauled for. Most wouldn't come back to you weeks,months or years later. Asking why you took most or all of the life out of the turbo bearings and seals.
Is it really too much time, bother and work to play it safe and bag the stack to prevent airflow and debris from entering the turbo?
" I have hauled equipment for years with out covering the exhaust pipe and have had no ill results." Are you telling use you are some hero blessed with super skills and super luck?

And if you don't have a bag, just close it up with some duct tape.

Case-IH and Kubota both recommend covering the exhaust.

Way back in '71 when I worked for a John Deere dealer is when a few guys with turboed 4020s learned that it IS necessary to cover the exhaust.