Re: Emissions...%-{

[Frank Deutschmann <fhd@interport.net>]

Christopher Ice x2136 sez:
> By changing the system to eliminate back-pressure, they would be actually
> *increasing* the emissions output even tho it may still be an acceptable level.
> This is in violation of the Clean Air Act and makes the shop subject to a
> $2,500 fine.

Yes, this is essentially correct -- any increase in cam overlap or reduced
exhaust backpressure will result in increased emmisions.  There are two
reasons: 1) an increased amount of the fresh charge is capable of migrating
out of the cylinder unburned (intake flowing right through the exhaust
valve), leading to increased hydrocarbon emissions; and 2) there is less
exhaust left in the cylinder (reduced EGR, so to speak), resulting in a
hotter combustion temp wich increases oxides of nitrogen emissions.

This is why hot cams and performance exhaust systems generally carry labels
that they are for off-road use only.  I don;t know of any cams and/or
exhaust systems (for any car) which have attempted to pass the CARB
exemption process.

-frank
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