<VV> turbocharger cooling

[jvhroberts at aol.com]

 Most of the L4s I've seen hang the turbos from the bottom of the exhaust manifold. And most of the water fittings I've come across use banjo bolts, but nonetheless... 



Most of the heat soaks back from the wheel and the turbine housing. These are the parts closest to the lubricated pieces. The manifold, at worst, just slows the cooling process due to its distance and the moderate thermal conductivity of cast iron. 



Bottom line, water cooling of a water cooled turbo should not be necessary if one idles the thing before shutdown. 





 





 



-----Original Message-----

From: FrankCB <frankcb at aol.com>

To: jvhroberts <jvhroberts at aol.com>; shortle556 at earthlink.net; fparker at umich.edu

Cc: virtualvairs at corvair.org

Sent: Tue, 26 May 2009 9:36 pm

Subject: Re: <VV> turbocharger cooling

















John,




???? I was thinking more of?INLINE 4 cyl engines like?the Dodge inline 4s with VNT-25 turbos.? Here's what the Garrett engineer said about using their VNT-25 in other applications:




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"The water cooling is intended for passenger car applications where the turbo is bolted to a heavy cast manifold with little airflow and many miles of stop and go service. The water cooling is not needed on a race car that isn't driven daily. Likewise, the water is not needed when the turbo is mounted on headers that don't store heat like a casting can. The water fitting is designed to mate with a steel tube flare nut. These can be removed and a different adapter can be threaded directly into the pipe threads and in the housing. Remember that the water is only for cooling during shutdown, the oil cools the bearings when the engine is running. When the engine is shutdown the heat stored in the cast exhaust manifold "soaks back" into the turbo causing the water in the center housing to boil."




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???? The 2 engines you mention are NOT inline 4 cyl engines, but rather V6 cyl. or flat 4 cyl. with two banks of cylinders.? 




?




Frank Burkhard




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In a message dated 05/26/09 05:45:38 Eastern Daylight Time, jvhroberts writes:









WHAT cars have the turbos on top of the exhaust manifolds? My 300ZXTT has them hanging from below it's exhaust manifold. Our Subarus have them mounted not unlike a Corvair. (Subarus don't have exhaust manifolds) Most L4 engines have them hanging below their exhaust manifolds. I've yet to see anything remotely modern that's not a truck or a piece of farm or construction equipment with the turbo on top of the manifold. 

It's the heat flowing back from the turbine wheel and the turbine housing after the cooling oil flow has stopped that causes the trouble. 

And these days, why use water, as a once through coolant? Intercoolers, better fans, etc., are a better way to go..

















-----Original Message-----

From: FrankCB <frankcb at aol.com>

To: shortle <shortle556 at earthlink.net>; Frank F Parker <fparker at umich.edu>; jvhroberts <jvhroberts at aol.com>

Cc: virtualvairs at corvair.org

Sent: Mon, 25 May 2009 10:42 pm

Subject: Re: <VV> turbocharger cooling









Many of the newer cars have their turbochargers sitting directly on top of the exhaust manifold which retains lots of heat on a shutdown.? If their engines?are not idled after a hard run and before shut down, the heat from the exhaust manifold really "cooks" the oil sitting?UNMOVING in the turbo bearing.? So if you don't have water cooling in your turbo, use a fully synthetic oil AND idle the engine a few minutes BEFORE shutdown to keep the oil flowing through the bearing while the heat has a chance to dissipate.









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