TURBO MAINTAINENCE

[KBB]

In the beginning....hahhaha most turbos simply were feed oil to lubricate the bearings, that were simple flat bearings not unlike what you'll find in the bottom end of your motor. The shaft spins in the bearing and the oil lubricates it all. When the turbine housing is very hot and you switch off your engine, the oil in the bearing race remains there because the engine is not running the engine is not pumping the oil through the cartridge or the bearing housing if you will. When oil remains in the bearing race when the turbo (being the cartridge and the turbine housing both being cast iron elements) is extremely hot the oil gets extremely hot. Oil doesn't like getting extremely hot and at high temp carbonises or breaks down and leaves deposits. Oil also does not transfer heat to adjoining oil very well either, which really doesn't matter, because when the engine is off, there really isn't any oil around in the cateridge other than the bit trapped in the bearing race anyway. SO the turbo timer was invented. When the ignition was switched off the engine would keep going and pumping oil through the cartridge of the turbo and the bearing race. The exhaust gases produced at idle are not terribly hot and as the car idles, the turbine housing and the cartridge and the bearing race all cool down and the shaft spins very slowly, itself not generating much heat on the bearing surface. After a minute or two, all temperatures reduce to a level whereby when the engine is switched off, the bearing race is not hot enough to carbonise or coke the oil and hence, the next time you start up there are no carbon like deposits on the bearing race to f*ck up your bearing or shaft. When the bearing and shaft are healthy, the seals are not stressed either.

When you don't idle down your non water cooled turbo (oil cooled is a misnomer really cause without the oil you would not have a turbo) it really doesn't last long. Just ask early ET/EXA owners. When you do, it last for ages.

But the turbo timer is really not something passenger car manufacturers could fit from the factory. What factory car come with one. What factory would fit a device that left the car running when you turned it off and locked it up and walked off. People (Today Tonight type viewers) would be outtraged.

Hence the water jacket turbo was devised!!! Water is an excellent heat exchanger and heat travels well through a body of water. Hence, when you turn off your hot turbo with water jacketed cartridge, the oil stops flowing, but the water jacket effectively cools the cartridge, shaft and bearing race sufficiently to avoid cooking and coking the oil in the bearing. Shaft and bearing stays healthy as there are no cooked on oil deposits and turbo is OK. As the water gets heated by the hot cartridge, the heat transfers out through the entirety of the engines water because all the water in the engine is joined to other water, unlike the sh*tty little bit of oil left in the cartridge.

The moral of the story is with water jacket turbos you don't really need the timer as you do with the non water cooled turbo.

Garrett who produces the XR6T turbocharger say timer is not required at all for the reasons outlined above. That said however, if you really have been leaning on it around a track all day, it is better to allow the water to do its job assisted by the water pump cooling things thru the radiator, cause water temp rises after shutdown and it is also beneficial to keep that oil flowing thru until the oil temp comes down to a pleasant level, to get the best of both worlds.

KB

[voy74656]

your 1 smart cookie KBB - it all makes sense now

[bcl]

KBB,

Sounds like your almost as old as me.

Pretty well spot on.

I had a rajay turbo back in '82 in my Sigma; blew a few oil seals.

My '84 ET had a Garrett T2 from memory, and that was oil cooled, and I replaced that with a water cooled T2 in '86 after a few oil seal problems.

The last time I actually had a turbo problem was back in '91 with a hybrid T03/T04, and not 1 problem since with any of the turbo cars.

I haven't used a turbo timer, let the car idle down only after hard driving, and try to change the oil every 5-6k.

Brian

[Guest]

granted water cooled turbos are less likly to have dramas but id sill try and cool the turbo down before switch of one method ive used has been ok im now a few minites of getting to my destination ill take it easy till I get there efectively giving it cooling time and the other is temp operated water pump!

[bcl]

The reality for me, living in Sydney, for most trips that I do is that often the last 2 to 5 minutes are 50kph zones, where I take it easy, so that is a cool down period anyway.

[ChargerMal]

But the turbo timer is really not something passenger car manufacturers could fit from the factory. What factory car come with one. What factory would fit a device that left the car running when you turned it off and locked it up and walked off. People (Today Tonight type viewers) would be outtraged.

Mitsubishi Starion had a 45 sec Turbo cooling Idle cut off.... :cool:

Edited 27/12/04 07:47 AM by ChargerMal