[SEL] OT PA trip & fuel costs

[JR504 at aol.com]

In a message dated 6/6/2007 4:37:03 P.M. Eastern Daylight Time,  
bill at antique-engines.com writes:

Note on  gas engines, they have INCREASED compression ratios and are using
fast burn  chambers.
Remember the compression ratios of the 60's and early 70's were  in the
10:1 and 9:1 range, then dropped to 8:1 in the green decades - they  are
back up.
Wonder why??



The major reason compression ratios increased a few years back was that the  
EPA was focusing on cold start hydrocarbons.  I forget the exact numbers  they 
were quoting, but I remember them saying that cars released more raw  
hydrocarbons out the tailpipe in the first few miles (before the catalytic  converter 
was lit) than they did in the next 50 miles of driving...or something  like 
that.  They were looking at all kinds of solutions like heated  catalytic 
converters.  These things had electric heater grids that would  heat them to 
operating temps before the driver could start the car.  They  also looked at 
hydrocarbon absorbers like the ones Toyota used on their hybrids  for a few years.  
Eventually they settled on bumping the compression ratios  to get the cold 
start hydrocarbons in line, and then feeding the engines  increased EGR gasses to 
deal with the increased NOx emissions caused by the  higher combustion temps.  
Joe Rappa
Mexico, NY



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