Re: Full throttle switch

[brads@mindspring.com (Brad Sheridan)]

Shad wrote:
>Yeah, that's right.  It's certainly no mechanical mystery to see the
>throttle body pulley thinger kick the switch when its wide open, and I
>have used the manual closing of the switch to keep it from dying while
>under the hood.  My question is why is it there?  It adjusts the mixture
>to something better which means that it must not have been quite right
>before the switch kicked in.  Does this mean that maybe the mixture
>ratio was set to yield optimal anti-"smog" mixture, i.e. perfect burning
>where all fuel molecules and oxygen molecules are used in the chemical
>reaction, and that making the mixture richer provides more power?
>Otherwise wouldn't the mixture be set at optimal mixture for power and
>therefor no further adjustment necessary?


   Thats pretty much it. When cruising, or at non Wide Open Throttle(WOT)
conditions, the O2 sensor is used to keep the engine running around the
stoichiometric air fuel ratio(14.7:1), which theoretically means the most
complete combustion of air and fuel in the chamber, and lower emmisions.
When you hit the switch it richens the mixture, lowering the air fuel
ratio, and tells the computer to ignore the output of the O2 sensor.
Maximum power on most cars is found by richening it up to the 12:1 to
12.5:1 air fuel ratio range. I don't know exactly what VW richens it to,
but probably somewhere in this range.


Brad


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