SV: Ignition retard knock sensor.

[d houlton x0710]

Gustaf Ulander wrote:
> 
> Hi
> 
> How about the Saab APC (automatic performance control) system? Designed to
> work on a tuboed engine, monitors knock and lowers the boost. Adjustable

I've seen the pages on the APC, but in my case it wouldn't work.  It's 
only useful if you're using higher boost than the wastegate actuator would
normally allow.  It works by bleeding off the pressure signal to the actuator
giving higher boost.  When knock occurs, it stops bleeding off the pressure
so the wastegate opens earlier, cutting boost.  But, it can only go as low 
as the actuator will allow when getting full pressure signal.

For me, that is 9 psi.  I'd need to switch to a new actuator or lengthen
the arm on it to get max un-bled boost at say 5 or 6 psi, then use the APC
to allow boost up 9 psi for it to work as designed.  It could then drop 
boost back to as low as 5 or 6 psi when knocking.

Hmm, maybe I could cut a section out of the actuator rod, thread the cut
ends and use a turnbuckle and jam nut to make it adjustable?   That doesn't
sound all that complicated.  And it's fail-safe.  If I screwed it up and 
stripped threads or the rod broke or whatever, the wastegate would open 
freely giving probably almost no boost.  9 psi is actually much higher than
I had anticipated and I don't hardly ever hit it anyways.  The APC then 
could work.  It's pretty cheap too from a junkyard.


> too. See http://hjem.get2net.dk/bengaard/apc-syst.htm or
> http://www.teleport.com/~bertram/volvoapc/ for descriptions on how to adapt
> the system to another engine. Guess you have to be cautious that the sensor
> react to "your" frequencys though...

Agreed.  That seems to be crux of the matter for any knock detection
system.  I've found 2 or 3 reviews of the J & S system on Miatas though
and they all seem to be extremely pleased with the results.


--Dan
houlster at inficad.com
http://www.inficad.com/~houlster/amigo.htm