[urq] Water Cooled Turbos

[QSHIPQ at aol.com]

In a message dated 2/16/01 8:20:37 AM Central Standard Time, 
isham-research.freeserve.co.uk at pop.pol.net.uk writes:
>If there is a piston ring issue with WR/WX engines in North America, I
>strongly suspect it's associated with emission controls.  The WX has
>at least partial electronic mixture control - I believe North American
>WRs are similarly fitted.  These systems reduce full throttle enrichment
>very rapidly when the throttle is closed, leading to the engine running
>very lean for a short period.  This generates enormous heat.

Again, you misunderstand turbo CIS theory.  The WX will actually increase 
fuel in the engine on closed shut throttle, leading to the engine running 
very rich for a short period.  Common problem on all pre 86 (usa) cis turbo 
cars.  Rich closed throttle spikes were the reason the later MC (1986>) used 
the decel valve. You have your understanding completely backwards again.
 
>  I might say the same.  I had a quick check round with some others who
>  see WR engines at least once a week - none of us has ever seen
>  heat-related damage to piston rings.  Bore ovality and bore damage by
>  foreign objects make up the vast majority of strip-downs.
>  
>  Scott's advice to a UK owner is thus rubbish.  If my word on this is not
>  enough, he is free to contact Roger Galvin (who has two WRs in bits
>  at this very moment), Simon Gilmore (who's just finished putting one
>  back together), Martyn Parker (who's done literally dozens if not
>  hundreds) or Aelred Smith down at Dialynx.
>  

Let's be clear here Phil, my advice to *anyone* with a oil cooled turbo, 
would be that the benefits of a water cooled turbo *INCLUDE* lower piston 
ring temps, in hot running and hot shutdown modes (or you can explain to me 
how I misread 860103).  I could care less if you have thousands of teardowns, 
in this case there is no question that the longevity of piston rings (and 
just maybe *ovality*) from lower temperature cycling is one of the benefits 
of WC turbochargers.  Your addressing the emission controls as a reason for 
the 'cross the pond' experience, really seems somewhat curious, given that 
EGR systems lower combustion chamber temperatures, especially in turbo 
motors.  More SAE papers on that for you.

My only questions would be:  In these thousands of teardowns in the UK, are 
the piston rings being replaced as a matter of course, or a matter of need.  
If it's a matter of course (as I suspect), then the point is moot.  What 
tests would you or your references perform wrt heat cycles vs brittleness of 
piston rings to solidify your argument?  Is reducing piston ring temps a 
benefit in a turbo motor?

I'm happy to talk to any of your referenced sources.  I doubt any of them are 
performing these teardowns without replacing the rings as a matter of course. 
 That doesn't change the fact that WC turbos reduce piston ring temps.  

But I haven't done hundreds of teardowns either.  Here, I'm happy to look at 
the volumes of temp data vs turbo generations and put forth a recommendation 
with sound theory and application attached.

Your opinion and others experience regarding actual piston ring failures is 
noted.  Really doesn't change much in terms of water cooled vs oil cooled 
turbos inherent heat problems, including piston ring temps.  Maybe it's 
"failure" that you are incorrectly focusing on.


Scott Justusson