SAFC II Knock Readings, whats your base reading? Options

[ghostdog]

What kind of readings are you guys getting from the knock sensor on your SAFC II's? I'll post what mine is tomorrow, but I'm worried I might be getting some knock. Thanks in advance.

[97sccelica]

mine usually stays at 0 and spike to as high as 40 when under boost

but it only stays high for a split second

where do you have your safc2? when it gets hot it gives high knock values

[SpedToe169]

The temp of the SAFC itself really shouldnt matter. Where did you hear this? The temp of the engine and the condition of the oil does matter. I zeroed mine after just warming the engine up (water up to temp). This wasn't enough. I had a long drive to go on after that (5 hours). Throughout the drive the corrected knock reading kept going up and up and up. What I believe is happening is that the oil breaks down slightly and the valvetrain makes more noise throughout the long heat cycle of the oil. This shows up on the knock sensor as knock. It sounds like the spiking under boost might actually be the onset of some knock. Now that mine has been zereoed after the oil has reached an equilibrium I rarely show anything above zero. Once in a while it registers like 20 but it does it at idle and I'm certain its just hearing valvetrain (or some other erroneous) noise.

[ghostdog]

Thanks for the replies guys. I know what 97sccelica is saying re: the knock readings going up if the unit is hot. I've found if its sitting in sunlight for a couple hours it'll start giving erroneous knock readings. But I don't think thats a issue with mine since its rather cold out here and I've made sure my s-afc stays cool.

I think the knock sensor was zero'd right after the car was warmed up, and the base level is set at 20 @ idle and 130 @ 3650 rpm. I've found when I drive my car hard with no settings the knock goes as high as 40 (additional to base level). However with the settings I am using the knock can go even higher for a split-second. I know this isn't good for my car as I haven't had it profesionally tuned so I've reverted back to stock settings, but I'm still wondering what kind of levels everyone else is getting. Could this just be excess vibration, or perhaps I need to re-zero once the oil has reached equilibrium like speedtoe suggests.

Thanks again for your help.

[SpedToe169]

Thats interesting that it seems to be dependant on the temperature of the unit. Kinda scary really.

Ghost Dog, I'd just rezero it when its good and warmed up and not worry about it. On an NA car with stock timing you shouldn't ever have any problems. Remember, the factory tune is supposed to be really knock resistant and tolerant of really ****ty gas. Only when you start making big changes to this do you need to start worrying.

[ghostdog]

yeah I know its nothing to stress over, but I also don't want any premature problems. I think I'll reset my timing to 12 degrees and re-zero the knock sensor after some spirited driving. thanks again for your replies. and if your interested I found a good topic on the subject:

http://forums.evolutionm.net/showthread/t-52300.html

[SpedToe169]

Good thread! Bushur really knows his stuff. My base settings are around 195. With that I've never seen a reading above about 35 and thats almost exclusively at idle. Its starting to make me wish I had my oil pressure gage in...making me nervous.