Can frequency valve be removed???

Can the frequency valve be removed if the O2 feedback loop is not going to be used? IS there anything else that would need to change other than a line from a 78-79 SC? It is my understanding that if the O2 sensor is disconnected, then the frequency valve defaults to 65% duty cycle. Is there a reason you could not bypass the valve and reset the fuel mixture at the fuel distributor?

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Daniel Tisserand
1981 SC

If you want to remove the frequency valve, I believe you need a different (K-Basic style) fuel distributor with 2 less holes in it. There is no reason you could not bypass the valve and reset the mixture. This is how K-basic works and the freq valve/O2 sensor system is an "add on". An easier alternative may be to make a SS fuel line to connect in place of the freq valve.

However, I really don't think this is worth the effort and will not give you an appreciable difference performance, unless you have some unique application for your system.

The frequency valve functioned to lean out/vary the mixture set by the fuel distributor when the O2 sensor detected high emissions. It does this by returning more or less fuel to the fuel tank return line. If this amount is fixed (ie 65% with O2 sensor disconnected), you should be able to just set the mixture to a stoichometric ratio of fuel/air, and the freq valve cannot change this b/c it cannot alter fuel pressure when it does not cycle. So whether the freq valve is stuck at 45%, 55%, or 65% should not really matter as long as you have the correct ratio set via the mixture, as long as it is stable. I guess you could argue that the lower chamber pressure on the car would be lower if the freq valve is not stuck open 100%, but I really dont think this would make a difference in how your car runs or performs.

Hope this helps.

Nick.

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Nick Shumaker
1982 911SC Coupe
nickshu@yahoo.com
PCA -- Rocky Mtn. Region