Knock with SAAB APC

Mihnea Cotet mik at
Fri Jan 9 11:37:58 EST 2004

Becase once they have been overtorqued, you can just throw them away. The 
knock sensors are piezoelectric pickups, about the same as on guitars. If 
you overtorque them, you just stretch them and alter the frequency range 
that they're able to listen to. And in that case, the ECU won't be able to 
"hear" knock anymore, because knock will have a different frequency and the 
ECU only knows about one frequency range (which I can't tell off the top of 
my head but I could dig it up)....

So be careful guys, if you ever get to remove the knock sensors, make sure 
you torque them properly, and use new bolts every time :-)


At 11:33 9/01/2004 -0500, Brett Dikeman wrote:
>At 5:06 PM +0100 1/9/04, Mihnea Cotet wrote:
>>I've had a few occasions where I was being forced to tune 20vt engines by 
>>ear due to overtorqued knock sensors that didn't give a correct output 
>>signal when knock occured and the ECU didn't do anything against it.
>Why didn't you guys just re-torque the sensors? :-)
>"They that give up essential liberty to obtain temporary
>safety deserve neither liberty nor safety." - Ben Franklin

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