<VV> Stoich Operation Re: Emission vs. Mileage Re: Road test No Corvair

[FrankCB]

Bob,
     Good point!  During the time our Corvairs were produced, the means of controlling A/F were quite crude by today's standards.  So it was much SAFER to design our cars so the carbs operated on the RICH side of stoichiometric to be sure the cars never went over to the LEAN side which could bring combustion problems since there was no electronic device to retard the timing.  Nowadays with much more precise computer control on EFI and especially the FEEDBACK from the O2 sensor in the exhaust as well as knock sensing to provide retard, I believe we could have cars that operate (under light load) leaner than stoich.  EXCEPT the NOx emission requirement has gotten much tighter so the present designs generally try to operate AT stoich for best mileage while still keeping NOx low.  NOx emissions increase significantly once the A/F goes LEANER than stoich.  But our Corvairs, if they are tested at all, are only expected to meet emission regs that were in effect in the 60s and NOT the current regs.
     Regards,
     Frank Burkhard

In a message dated 06/26/09 15:29:21 Eastern Daylight Time, BobHelt writes:
In a message dated 6/26/2009 12:15:05 P.M. US Mountain Standard Time, frankcb at aol.com writes:
Our Corvairs, for example, can run with LEANER than stoichiometric (about 14.7:1 A/F ratio) which the narrow band O2 sensors lock the computer control in for cruising on the newer cars.  Our Corvairs can run leaner than that for higher gas mileage cruising if we use electronic fuel injection and a WIDE band O2 sensor to control it.  
Frank,
Maybe so, but according to the only real data we have, the official Corvair/Chev engine test reports, stock Corvairs NEVER ever got close to Stoich. Apparently the engineers were so afraid of possible preignition and/or detonation that they saw to it (according to the data) that no Corvair engine ever ran lean. To run a Corvair as lean as you are suggesting would seem to be inviting problems if one is to accept the test data in these reports.
Regards,
Bob Helt