Originally Posted by IceY2K1

It's whatever gadget their usings output of current, at that moment, knock count.

What that's actually measuring/showing, I don't know.

Originally Posted by DSMJim

Steve go back to the other thread I spoke a lot about this subject there.

The long and short of it is on an OBD2 car this doesn't really apply, it's more an an OBD1 issue.

Originally Posted by IceY2K1

Got link?

+10

Originally Posted by DSMJim in the 4th Gen Forum

Ok, this is the funny thing.. Knock count I'm refering to is what is viewed on a OBD1 DSM, it's so many counts per a period of time. I don't know what that period is, doesn't really matter just as long as that count doesn't exceed 40 at the very most (even that's dangerous). Many people who read DSM tuning guides don't know what the number mean or how they apply to a different car.

OBD2 doesn't see knock in a number like 5-10 as I have been refering, it shows a raw number that the computer deciphers. I believe it's given from the sensor in Ohm's or Voltage and is then converted by the computer into a number which it uses. If you hook up a SAFC2 and look at the knock readout during normal driving you will see numbers like 40-50 showing up but it's not knock because cars don't knock at part throttle at all, pretty well impossible under there is some big *** hill your trying to climb or something that puts lots of load on the engine. That makes the number from the stock knock sensor pretty much uselss.

On OBD2 (or OBD1 for that matter) when you get lots of knock timing will start to get pulled. So your best way to monitor knock is by watching timing. If your at WOT and 4500rpm your timing is 16deg, then 5000rpm its 17deg then 5500 it goes back to 15deg you know you had knock between 5000-5500rpm because timing got yanked 2deg right there. Timing should gradually ramp up with RPM to redline. If you start at 16deg at 4500 and slowly end up at 22deg at 7000rpm then that's a pretty good curve and it goes up one or two deg every 500rpm or so, your golden. It doesn't matter how much knock the computer is seeing, because its not enough to pull timing back. If you keep timing happy and rising nicely though the rpm band then knock WILL be under control. Doesn't matter if it's zero or 1000 the computer will determine if and when to advance timing based on what the knock sensor send back to it. If your Air/fuel ratio is good then you will have little or no knock and the computer will advance timing normally.

It all comes down to Air/Fuel. Don't aim for a specific number like 12:1 if your turbo because you heard thats the best. If your car ramps timing up faster at 11.6:1 or something like that then it's happier being there then leaner at 12:1. Basically get your A/F into the right zone for your application (11.2 - 11.5:1 for Nitrous, 11.5-12.0:1 for Turbo and 12.9 - 13.3:1 for All motor all at WOT) then make adjustment until your timing ramps up the fastest and goes to the highest number. Thats then you know your running the right air/fuel that makes your motor happy, timing is good and knock is under control and your making the most power.

Rich cars lose power, lean cars make power but risk blowing up, the first sign of which is knock then pistons with holes in them. You want to stick to the safe side on the street so tune rich (not crazy but it your turbo shoot for 11.5:1 to start not 12.0:1) and go from there. Once you have spent some time tuning your car and going to the track and seeing what works for you, you will know exactly what makes your particular motor/setup happy and make the most HP. Then you won't have to listen to guys on the internet tell you what to do because you will know what to do.