[urq] What causes knock ?

[Martin Pajak]

It could also be a coincidental.. pressure transducer failure.
Anything above 5psi would cause pinging.. on the plus side it was very
powerful at low RPM and boost spool up was excellent.. dues to ignition
advance.

Cheers
-- 
Martin Pajak

http://www.quattro.ca

1982 Audi Ur-quattro (50,000 mi) new project
1983 Audi Ur-quattro (85,000 mi) Concourse d'Elegance
1985 Audi Ur-quattro (212,000 km) Euro spec. import mit 3B :)
1987 Audi 4000s quattro (205,000 km) wintervagen mit 7A :)

> Louis-Alain Richard
> My car developed some strange sounds, and one is sounding a lot like
> knock. It happens only under boost, and it is sporadic. But it scares
> me, specially after what happened to Dennis...
>
> The second strange sound is identified, it is the fuel tank collapsing
> after a few minutes on the highway, a big "bong" sound. Today, as the
> fuel tank was nearly empty, I stopped and noticed that the fuel cap made
> the "iiisssssss" sound of air entering the fuel tank. So there are no
> fuel vapors going back to the tank, IMO.
>
> Now, are these 2 problems related ? Can a fuel tank that is under vacuum
> stops the fuel flow to the pump and starve the engine ?
>
> Then, how can I find the problem with the fuel vapor circuitry ?
>
> And my title question remains: what causes knock ?
>
> Louis-Alain
>
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