What's the danger?
New User
Joined: Feb 2002
Posts: 20
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The real reason to let it idle before shutdown is to let the turbo spool down to a safe speed before you shut it off.
The turbo does not have any bearing or bushings in it (unless you have a bb turbo)The turbine shaft rides on a cushion of oil inside the center section and when the oil pressure stops the turbine shaft drop to the bottom of the housing.Now picture that turbine shaft spinning at 20,000 rpms as it does when its spooled up,and you shut the oil supply off.The shaft will, in time wear into the housing and cause an inbalance.If this continues to happen you will soon hear a very loud bang followed by majior oil loss when it blows apart.
This happens all the time to Mack and Cummins engines when they are not allowed to idle for 3 minutes before shutdown.
The turbo does not have any bearing or bushings in it (unless you have a bb turbo)The turbine shaft rides on a cushion of oil inside the center section and when the oil pressure stops the turbine shaft drop to the bottom of the housing.Now picture that turbine shaft spinning at 20,000 rpms as it does when its spooled up,and you shut the oil supply off.The shaft will, in time wear into the housing and cause an inbalance.If this continues to happen you will soon hear a very loud bang followed by majior oil loss when it blows apart.
This happens all the time to Mack and Cummins engines when they are not allowed to idle for 3 minutes before shutdown.
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
Originally Posted by GeoffNJ
I let mine idle the whole time I'm in there. I'm not doing damage to the turbo because some leftist, 1974 Volvo-driving, Berkinstock-wearing moron with some half-assed biology degree says it's bad for his lungs.
Stop beating around the bush Geoff, just come out with it so we know how you feel.
Elder User
Joined: May 2003
Posts: 650
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From: Leesburg, NJ
Originally Posted by Tenn01PSD350
Stop beating around the bush Geoff, just come out with it so we know how you feel.
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
No problem Geoff, that case of the a$$ guy goes for me too 'cause I don't have much use for tree huggers with misplaced $$ and time on their hands. They need to get a job or give their misguided money to a worthy cause and not hammer your working taxpaying average Joe. If I want to idle for 30 mins here in TN then that's what I will do, and when I can't, I will move.
Last edited by Tenn01PSD350; Mar 14, 2006 at 11:50 PM.
Elder User
Joined: May 2003
Posts: 650
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From: Leesburg, NJ
As strokin_it said, it's the same amount of burned fossil fuel no matter which way it's done.
If it wasn't for the fact that my family has been here for 350+ years, I'd leave. We're just stubborn, I guess. There are a lot of people from this state headed your way, Mike.
If it wasn't for the fact that my family has been here for 350+ years, I'd leave. We're just stubborn, I guess. There are a lot of people from this state headed your way, Mike.
Senior User
Joined: Jan 2006
Posts: 374
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From: Las Vegas,nv
Originally Posted by strokin_it7.3
yes, both of these guys are right, but i will throw in my two cents too. usually, the flashpoint of a good oil is 450-500*F. that means, that if oil is heated to that temperature, it will ignite. now, in the engine, if you don't let the oil pass through and through to cool the actual turbo and the gasses passing through it to a temperature below the flashpoint, the oil will bake on the shaft of the turbo, some call it "coking", and it leaves a varnish on the shaft. over time, this varnish can accumulate, and can eventually make it's way into the bearings, which can stick the bearings, preventing the turbine wheel to spin without restriction, which is just overall bad for it, aside from obvious reasons. we have a turbo out of a small riceburner in our classroom, that wasn't allowed ample cooling time, and you can plainly see how the shaft was varnished and the bearings were sticking, it eventually began to pass oil out of the turbine.
