Turbo Charger Cooldown

[ichn2go]

When returning home my street is a half mile long. I travel this at 15/20 mph and then back into my drive at idling speed. Is this a long enough time for the Turbo Charger to cooldown or do I still need to idle the engine for awhile? How Long? Good Miles

[ichn2go]

When returning home my street is a half mile long. I travel this at 15/20 mph and then back into my drive at idling speed. Is this a long enough time for the Turbo Charger to cooldown or do I still need to idle the engine for awhile? How Long? Good Miles

[gunny]

I would think that would be adaquet. The cool down usually discussed is to cool the turbo charger. When under a hard pull and the turbo working, the bearing section of the turbo gets very hot. Oil cools and lubricates the bearings. If you shut the engine down when still very hot, the oil can "coke" and block oil flow resulting in turbo bearing failure.
In our business we routinely load test diesel generators at 100% load, at that load level the turbo and exhuast can glow red from heat. When the engines are unloaded, the red glow goes away almost immediately and by observing the pyrometer we see exhaust temperatures drop from the 900 degree ranges down to 300 or so in less than 3 minutes. Keep in mind these engines are still running at 1800 rpm so one running at idle speeds of around 800, it would cool quicker. If it would make you feel better or safer, by all means run it another couple of minutes.

[John_Canfield]

Jim- what I have heard in the Cummins seminar I attended at the Perry rally was that a prolonged cool-down was not necessary in normal circumstances. They said just about five minutes at or near idle would be adequate - "by the time you get to your campsite, all is well with the turbo.".

Like gunny says - if you have hill-climbing time and you are running hotter/more loaded than normal, then you just need to keep it at idle for a few more minutes.

I recently have noticed on my Cummins ISL that with a cold engine the turbo doesn't spool up after starting until a few minutes have passed. Then you can hear the unmistakable turbo whine - sort of sounds like I'm on the flight line at the airport. I suppose this is a safety factor for the turbo bearings - don't really know but this is a good guess!

--John

[gunny]

John:
Cold oil is thick and sticky (relatively so) and tends to drag the turbo down some, once the oil temperature gets up there the turbo will spin a lot more freely.