<VV> turbocharger cooling

[FrankCB]

Dave and Timothy,
     Well, I suspect that the CHT indication is not proportionately related to the temperature of the turbocharger wheel or the oil going through the the turbo.  When I was driving my 180 regularly to work, the CHT would show 400 deg.F. for lightly loaded highway cruising.  Under full load and 8 psi of boost (16 in. Hg) the CHT would go to 450 deg.F. not a really big change, but I'm sure the turbo wheel temp would change by a much greater amount.  So I would always idle the engine a few minutes just to be on the safe side before I shut it down.
     The thermistor and gauge setup in the Corsas is not too accurate.  Where it should be used is to establish a "normal for your car" reading for low load highway cruising and then you can see how much it increases with full load, high boost.  Incidentally, if you keep up the full boost for more than a few minutes you will probably find that the CHT just keeps rising since the cooling fan is unable to control the engine temp without additional cooling assistance (like water injection internal or external).
     Yes, if you wrap the exhaust piping from the manifolds to the turbocharger you will significantly reduce turbo "lag" AND increase the boost (say from 8 psi to 10 psi on the same long hill at the same speed).  However, when I did this to my stock piping, after 6 months the piping disintegrated from overtemperature according to the metallurgical engineer I showed it to.  Also, I noticed that the increased temp caused increased expansion of the crossover section which tended to loosen up the bolts connecting it to the manifolds.  I guess stainless steel piping with an expansion joint is the answer.
     Frank Burkhard 

In a message dated 05/28/09 11:00:05 Eastern Daylight Time, shortle556 at earthlink.net writes:
Hi Dave, I'm assuming you have changed the thermister 3 times thinking it was not reading accurately. I don't think any of them were very accurate, just an indication of what was going on. Oil temp. was never actually monitored or checked on Corvairs though they (Chev.) knew it was an issue, hence the engine oil cooler with suggested cooler maintenance (removing cooler cover and cleaning fins). You mention "turbo temp.". Are you referring to exhaust temp. at the turbine shaft, charge air pressure temp. going into the intake crossover, or temp. of the oil at the center section? I remember there being kits to wrap the exhaust pipes going up to the turbo. I think it was to get quicker boosting (less lag) and less warm up time but I'm not sure. 
Timothy Shortle in Durango Colorado 

-----Original Message----- 
>From: Dave Thompson <dave.thompson at verizon.net> 
>Sent: May 27, 2009 11:32 PM 
>To: 'Dave Thompson' <dave.thompson at verizon.net>, HallGrenn at aol.com, JVHRoberts at aol.com, FrankCB at aol.com, shortle556 at earthlink.net, fparker at umich.edu 
>Cc: virtualvairs at corvair.org 
>Subject: RE: <VV> turbocharger cooling 
> 
>I forgot to mention earlier, I DO realize that there is a difference between 
>cylinder head temp, oil temp and turbo temp but they ARE related. I also 
>know that CHT changes faster than oil temp. I don't know about turbo temp. I 
>would imagine that it follows oil temp to a certain degree (no pun 
>intended). I also guess that turbo temp is mostly affected by exhaust temp 
>but is regulated by oil temp as the oil runs through it to lubricate the 
>bearings. Since I only have a CHT and the temps are rather stable with 
>driving style around 375 to 425, I use it to determine the overall temp of 
>the engine. Am I right in my assumptions? 
> 
>Dave Thompson