[V8] sanity check, what, from a V8Q owner?

Bastian Preindl bastian at preindl.net
Tue Mar 18 14:41:44 PDT 2008


I also own the self studying plans of the Audi V8Q which detail the Hall 
sensor and ECU behaviour in cause of fault. The BTDC is reduced afair, 
that's it and the ignition point sensor values are used as substitution. 
Nevertheless we've spectated that for some reasons a defect Hall sensor 
causes the engine not to start - believe it or not.
By the way: Also the V8 needs to know if you are at TDC on #1 - that's 
what the ignition point sensor measures. The Hall sensor is only needed 
to correct differences caused by lengthened or not perfectly calibrated 
timing belts and when being up in high UPMs. For all other situations 
the TDC on #1 could be easily calculated by knowing the ignition point 
sensor value. The situation is similar on the I5.



cobram at juno.com schrieb:
> I think the only difference would be whether the Audi is a V8Q or not. 
> Because of the even number of cyls and the distributors firing at fixed
> degrees, the ECU in this case does NOT need to know (unlike an I5) if you
> are at TDC on  #1 or not to run.  It does effect the knock sensor  (which
> default to 16 deg. BTDC) making for less than optimal performance, but
> not related to starting at all.
> The hall signal is used with other parameters to time injector firing to
> reduce emissions, aside from this it's like a CIS system in that it
> doesn't matter for normal operation.
> Former lister Keith had a very good write up on it take from the Audi
> literature, it's probably in the archives somewhere.  
> Easy to prove, disconnect the hall sender @ the distributor on any V8Q
> which doesn't have a preexisting problem and see for yourself.  

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