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can somebody pls explain to me what the frequency valve does on 84 gti? and how come the euro fuel distributor doesnt have one and make more hp?
 

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Re: frequency valve?? (geeteei)

The frequency valve is part of the oxygen sensor system which VW put on North American cars for emissions control. The O2 sensor ECU uses the frequency valve to adjust the air/fuel mixture. The euro-injection is a stictly mechanical system much like the older CIS systems. I don't know much about the euro system but I believe it runs a bit richer than the stock system and has better air flow.
 

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Re: frequency valve?? (Norm95)

I'm pretty sure it's because the Euro systems don't use an O2 sensor and don't need the same one that the US cars have. I believe that version of CIS just runs open-loop all the time.
As Norm pointed out, the Euro cars had different cams (G-grind). They also had higher compression (10:1) and I believe they used the Heron heads.
 

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Re: frequency valve?? (geeteei)

The heron head was used on early 1.6L european GTIs, a high compression engine, it had bigger valves and head surface was flat, the dish in the piston formed the entire combustion chamber. These head are very rare.
 

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Re: frequency valve?? (ABA Scirocco)

A friend of mine in New Mexico has 2 heron heads and another one on a car. He won't part with any of them. 2 of them are laying in his shop collecting dust instead of dusing ricers. shame shame shame
 

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Re: frequency valve?? (millerwj)

quote:[HR][/HR]I'm pretty sure it's because the Euro systems don't use an O2 sensor and don't need the same one that the US cars have. I believe that version of CIS just runs open-loop all the time.
As Norm pointed out, the Euro cars had different cams (G-grind). They also had higher compression (10:1) and I believe they used the Heron heads.[HR][/HR]​
Correct. BTW 1.6 GTIs used the heron head, 9.5:1, G grind for 110 HP. 1.8s used a milder N and ? grind with the same head we got, 10:1 for 112 HP.
 
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