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Posted by BlaaSaab [Email] (more from BlaaSaab) on Wed, 3 Feb 2010 20:39:38 Share Post by Email
In Reply to: Re: Knock sensor?!?, office boy, Wed, 3 Feb 2010 16:39:19
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The knock sensor isn't *in* the DIC, it *is* the DIC. It's not a simple microphone that "hears" the knocking like on other cars...this is Saab's explanation:

"Rather than utilizing an engine knock sensor, the Saab Trionic system analyzes the combustion process by applying a weak voltage across the gap of every spark plug after each combustion to measure the degree of ionization in the cylinders. The amount of current flowing back to the control unit is dependent upon the number of ions that have been formed, which provides a measure of whether the air/fuel mixture has ignited and burned correctly. If not, the system adjusts the fuel quantity, the Direct Ignition timing or the turbo boost pressure."

(This is why you have to use a certain type of resistor spark plugs, because if you use ordinary ones you lose this ability and your car won't be happy.)

For that reason, I don't know if it's even possible to wire an LED that indicates knocking that easily. You'd first have to find the signal going to the ECU, tap into it, and then probably figure out how to process it into a pulse that can be indicated by your LED.

I do know that if you have a 2000 or later 9-3 (or 1999 Viggen) with the Trionic 7 software, you can have your ECU reflashed so that it'll display knock counts (and lots of other data!) in real-time on your SID. But you'd have to do a bit of Googling to find out how to get that enabled.

posted by 71.181.236...

http://www.saabnet.com/tsn/models/1999/9993pr3.html

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