How to: Use an safc2 to monitor knock on the 3sgte Options

[lagos]

I recently upgraded my safc1 to the safc2. One of the new features in the safc2 is the ability to monitor knock. However after doing some research on the topic, I kept hearing everyone say that the feature doesn't work correctly with our cars because it seems to report a knock count, even when there is no knock.

I decided to look into this myself, especially since my car has had some detonation issues. I started to notice a patten in the knock readings the safc2 was showing. What I noticed is that the knock number was always higher when my car pulled timing, and alot lower when it was not. I decided to contact califcarm to help me figure out if what I'm seeing is correct. He was able to verify my theory and help figure out exactly what is value is knock and what is just normal engine noise by monitoring his JS Safeguard for a knock count and comparing it to what the safc was reporting.

Now before you try to monitor these values, you need to look at your safc2 owners manual to setup your noise profile. There is a knock menu in the safc, where you rev to 1500, hold the rpm, and sample the noise print. Then you do the same thing at 3400rpm. The safc then uses those two values to extrapolate the rest of the data for your noise profile.

Here is what we found:

0-169 knock = Normal engine noise with zero knock
170-175 knock = On the verge of knock. Car is most likely making the most power, but you are running on the edge.
176-185+ knock = This is where most knock happens. The stock ecu might not react to these values alone, but there is definitely some detonation going on.

Now its important to note two things. First, there is no one magic number that will make the car fall into safe mode from knock. Instead the ecu waits till a few knock events (a few small or a few big) before it falls into safe mode. I have seen my car go up to 185, and not pull timing. Then right after that run, I hit 172 and the ecu went into safe mode and pulled timing. This is because it already remembered the first large knock count... tried to correct it, but saw another smaller knock count and decided to step in.

The other thing that needs to be mention is to take these figures with a grain of salt, and use them at your own risk. Since every car has a different noise profile, its possible that these values might be slightly different from car to car. However they DO seem to be consistent for me and califcarm.

I would also love to hear back form a few safc2 users to see what kind of knock counts they normally get under different conditions. This could be very useful tuning tool, especially those trying to use the safc to tune with alcohol injection.