Protect Your Turbocharger

If your coach has a diesel engine, it almost certainly has a turbocharger.

Cummins VGT Variable Geometry Turbocharger

Cummins VGT Variable Geometry Turbocharger

And, if you ever have to replace the thing, it’s going to cost a lot of money.

You can greatly decrease your chances of ever needing a replacement by remembering just a few simple things.

When stopping after a hard run, never kill the engine without letting it cool for a few minutes first.

Never kill the engine while it is on “fast idle.”

Change your engine oil religiously.

Close adherence to those three rules will almost certainly assure you of a long turbocharger life, according to a Motorhomes of Texas news release by Mike Martinkus.

Now if you want to know the short version of “why,” read on.

Turbo’s are driven by the exhaust gas blowing out of the engine. That exhaust gas is piped to the turbo unit and causes an impeller inside the unit (think propeller) to spin and that impeller is mounted on a shaft that runs through the turbo housing to an impeller on the other side of the turbo body. That second impeller blows fresh compressed air into the engine and that compressed air gives the engine more power.

When the engine is at idle speed, around 600 rpm (revolutions per minute) the turbo impellers are spinning at several thousand rpm.

ISX15 for Heavy-Duty Truck (2013) produces 400-600 hp at 1450-2050 lb-ft

ISX15 for Heavy-Duty Truck (2013) produces 400-600 hp at 1450-2050 lb-ft

But, when the engine speeds up to just a thousand rpm (high idle), the impeller speeds increase to tens of thousands of rpm. When the engine is at highway speeds, the rpm of the turbo REALLY goes up—as much as 150,000 rpm. Yeah, that’s some spinning right there.

The turbo shaft spins so fast that it is very hard (read expensive) to manufacture bearings for a shaft that spins that fast so a lot of turbo’s shafts don’t have bearings but instead ride on oil. That oil is the engine oil which is supplied to the turbo under pressure by the running engine.

If the turbo does have bearings, those bearings are lubricated and cooled by the engine oil—that hot engine oil which is, in fact, much cooler than the turbo charger and its internal parts. It’s hot because remember it is driven by the exhaust—hot exhaust which gets hotter with increased rpm. The faster the engine runs, the hotter the exhaust, the hotter the engine oil becomes and the faster and hotter the turbocharger gets.

If you are driving hard, the engine is hot.

The turbo is spinning at 150,000 rpm and has reached 1,200 F. When you shut off the coolant supply (oil) by killing the engine, the oil that is in the turbo charger literally boils and cakes the shaft with burnt oil residue. That burnt residue does not make for a smooth spinning shaft and ultimately will cause the shaft to stall completely.

Bentsen Palm Village RV Resort Super Site

Let the turbo cool down for a couple of minutes before killing the engine. This diesel pusher is enjoying a Super Site at Bentsen Palm Village RV Resort south of Mission, Texas.

In addition to damaging the shaft the vanes that comprise the impellers are by necessity very light and very thin. Excessive heat and or lack of lubrication will eventually kill them. Those blades start flaking off and being ingested its bye bye turbo and maybe sayonara to the engine too.

Let the turbo cool down for a couple of minutes before killing the engine. Kill the engine from idle but give the turbo a chance to slow its spinning first.

Remember, keep the oil clean.

Worth Pondering…

“Get your motor runnin’
Head out on the highway
Lookin’ for adventure
And whatever comes our way
Yeah Darlin’ go make it happen
Take the world in a love embrace
Fire all of your guns at once
And explode into space.”

It could be the theme song of every RVer, though it’s not likely what Steppenwolf had in mind when they recorded Born to be Wild in 1968.

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