> The main disadvantages are the lack of mixture control. This will
> prevent the cat converter from reducing all three, (HC, Co, NOx),
> pollutants it is designed for. There is also a fear of it going lean
> which can melt valves and pistons. When the full throttle switch is
> activated the mixture will go rich for max power so that is not a
> benefit.
>

Yeah, running "open loop" on the O2 sensor will eventually foul and/or cook
your cat with unburned HC. Digifant responds to open loop by going pretty
rich, as it's essentially "flying blind" and a fouled cat is preferrable to
a cooked valve. NOx goes down, but HC and CO go through the roof-- to the
point where the cat can't handle it. My wideband O2 sensor readings showed
nothing less rich than like .95 in open loop. Everything else being equal,
disconnecting the O2 sensor shouldn't result in a lean condition, just a
fouled cat. Yeah, the most efficient way to get more power is to use the
system as Bosch designed it: make sure your throttle switch is functioning
and depress the gas pedal to the floor when you need the juice. Open loop is
just a big fuel waster.
--
John Bange
'90 Vanagon - "Geldsauger"