<VV> Cooling Boosted Corvairs Re: You know your Turbo is working when...

[FrankCB]

Tony,
     INMHO, the ever tightening environmental restrictions are REALLY what has killed use of air-cooled engines in cars.  Even water-cooled engines have a tough time meeting these restrictions from the short time they are first started until they reach about 200-220 deg.F normal operating temp.  But thereafter the water "blanketing" surrounding the engine limits the temp. swings to only a few degrees.  On the other hand, the air-cooled engines start from the same temp. but have to move up to say around 350 deg.F for "normal" operation and can easily swing to 400+ under load.  The turbo Corvairs can easily go to 450-500.  The nitrogen oxides (NOx) requirement was what really sank the air-cooled engine for automotive use.  NOx production is extremely sensitive to combustion temp climbing rapidly with even a modest increase in temp.  So I think this is what forced Porsche into going to water cooling for its cars.
     We can see this in the extreme case for NOx emissions from diesels.  With their 20+:1 CR, water-cooled diesels have an even tougher time than gas-engined cars meeting NOx specs.  Mercedes has a model that requires use of a urea solution being injected into the engine to counteract the NOx formation produced from a cold start.  Wonder what kind of alarm goes off for the driver if he lets the urea solution tank run dry??<GGGGG>
     Frank Burkhard

In a message dated 06/21/09 08:51:49 Eastern Daylight Time, tony.underwood at cox.net writes:
Scuttlebutt has it that Porsche went to water cooling in order to 
meet smog while still making respectable power, seeing as how they 
had already managed to extract ridiculous hp figures while using a 
boatload of cooling fins on the heads and jugs, much more than the 
average 'vair could ever enjoy.