letting your turbo cool after a hard drive?

[omodos]

Hi all, been looking at various sites regarding turbos and wondering if the below applies to X5 3.0d's as well?any ideas?also says you should let car warm up well before any sudden acceleration hmmmm

A problem often overlooked by first time owners of turbocharged vehicles is not letting the turbo properly cool down after being ran hard or for long periods of time. After shutting off the vehicle the turbo is still incredibly hot and the turbo no longer has oil circulating through it, this can cause the oil to cook and become hard leaving small deposits in side of the turbo which will eventually cause premature bearing failure. The simple solution is to let the engine idle for a few minutes after being ran hard allowing the temperature to come down to a level that will not cause damage. If you dont feel like waiting around there are many commercially available turbo timers on the market that will allow you to leave the vehicle idling for a predetermined amount of time with out worry of some one taking off with it.

[admranger]

The turbo spins at about 100k+ rpms at full chat. It is also bathed in exhaust gasses while running. Exhaust gasses that hover around 1100 deg F at full boost. Definitely want to let the engine idle for a few minutes after towing a heavy load or driving hard. Puttering around town is no big deal, but if you have your foot in the throttle, you should consider a cooling down period.

Warming up is somewhat important, though just idling a diesel usually doesn't do much to warm it up. Gently driving until the fluids come up to operating temps is a better option.

My experience is based on towing a 26' enclosed trailer with a crew cab diesel dually trucks, one which had an exhaust gas temp gauge. I've seen 1300 deg F exhaust gasses on short bursts w/a modified fueling program. It was no problem to regularly run all day long at 1100 deg F (post turbo temp measurements -- true temp probably 100 deg F higher).

[HPIA4v2]

Originally Posted by admranger

The turbo spins at about 100k+ rpms at full chat. It is also bathed in exhaust gasses while running. Exhaust gasses that hover around 1100 deg F at full boost. Definitely want to let the engine idle for a few minutes after towing a heavy load or driving hard. Puttering around town is no big deal, but if you have your foot in the throttle, you should consider a cooling down period.

Warming up is somewhat important, though just idling a diesel usually doesn't do much to warm it up. Gently driving until the fluids come up to operating temps is a better option.

My experience is based on towing a 26' enclosed trailer with a crew cab diesel dually trucks, one which had an exhaust gas temp gauge. I've seen 1300 deg F exhaust gasses on short bursts w/a modified fueling program. It was no problem to regularly run all day long at 1100 deg F (post turbo temp measurements -- true temp probably 100 deg F higher).

+1
I am doing it on the twin turbo N54 and twin-scroll N55 BMW engine as well, idling for a bout 1 min or so after prolong drive or hard drive.

But people on the E90 and E60 believe it won't be necessary since the modern BMW turbo has electric WP that keep running after shutdown to cool the engine/turbos. But it's a habit for me after my Audi ate a waste gate of my KO3 turbo once.

[J.Belknap]

Just don't beat on it for the last 5-10 minutes of the drive.

[i-want-in]

Originally Posted by omodos

Hi all, been looking at various sites regarding turbos and wondering if the below applies to X5 3.0d's as well?any ideas?also says you should let car warm up well before any sudden acceleration hmmmm

A problem often overlooked by first time owners of turbocharged vehicles is not letting the turbo properly cool down after being ran hard or for long periods of time. After shutting off the vehicle the turbo is still incredibly hot and the turbo no longer has oil circulating through it, this can cause the oil to cook and become hard leaving small deposits in side of the turbo which will eventually cause premature bearing failure. The simple solution is to let the engine idle for a few minutes after being ran hard allowing the temperature to come down to a level that will not cause damage. If you dont feel like waiting around there are many commercially available turbo timers on the market that will allow you to leave the vehicle idling for a predetermined amount of time with out worry of some one taking off with it.

*A piece of advice from the owner a more than a few turbo'd cars.*

Go buy a turbo timer. Or sit in your vehicle every time you drive and let it cool 3-5 min.
Dont build boost until the engine is up to operating temp.
Its that simple.

The turbo is probably gonna outlast the warranty even if u abuse it. Then its gonna fail right after.
The faster u accelerate, the more load you place on the engine, the more boost you build. It IS infinite, thats why there is a wastegate.
The only turbos that dont need a cooling down or warming up period are ceramic-ball bearing turbos.
If the engine is up to operating temp, the turbo has been there a few minutes at least. If your running the engine/turbo hard, your probably past operating temp on the turbine/bearing side. While that wont destroy the turbo in most applications, it will cause premature wear. The more you hold prolonged boost( such as top gear prolonged acceleration) the more the turbo is gonna operate outside the design parameters. Hence, premature wear.
Yes the oil will "coke-up" on the bearings. And yes there is such a thing as a cold seize.

Just go by a timer and move on with your life. Time is too precious to sit there all the time. A remote start isn't a bad idea either. Call it the joys of a turbo'd or diesel engine.

[omodos]

thanks for all the replies, great response.ta

[m5james]

I was gonna say, a turbo timer is what I've ALWAYS used in the past on various turbo cars I've owned in the past. It allows you to shut off the ignition, lock the doors and walk away while this little $100 box takes over the ignition and leaves the engine running for switchable preset amounts of time. It coneects to your ebrake, so if someone happens to get into the car while it's still running and doesn't have a key, the engine will die the second the ebrake is released. Wiring it into your car though, that will be the trick.

[J.Belknap]

Originally Posted by HPIA4v2

People on the E90 and E60 believe it won't be necessary since the modern BMW turbo has electric WP that keep running after shutdown to cool the engine/turbos.

Really? That's very cool. In my experience, water cooled turbos last a bit longer than non.

That combined with easy driving before shutting it down is more than sufficient IMHO.

[Snapper692]

General (unwritten) rule of thumb is to let your EGT's (if probe is before the turbo) cool to below 400* before shutting off...

[Laurence]

Also, don't forget the oil - fully synthetic oil will deal better with the high tempertures created in the turbo.

As mentioned, oil circulation stops once the engine is turned off, non synthetic oil can "bake" and block the oil ways cuasing eventual turbo failure.

I always let my engine idle for a couple of min when I stop - turning the engine off is the last thing I do before I leave the car.
120,000 miles and no turbo problems - I hope thats not the kiss of death!