Knock... SAFC II vs. Pocketlogger

[Velo_TalonTSI]

I'm getting two different readings for knock. Example SAFC reading 14 knk, pocketlogger reading 0. Which one should I go by?

 

[CanadianTSi]

The logger.

 

[Blk_99gst]

I wouldn't even tap your knock line for the safc; reason being it can cause false readings on any electrical signal; much like the blue wire back in the day.

I'd unhook your knock wire to the safc. Let the true knock signal get to the ecu, and then read with the pocketlogger how much knock the ecu is seeing. After all that's the only number that matters, the actual number the ecu is seeing...

Copy and paste about why you shouldn't tap the o2 wire for the safc, also would apply to the knock wire:

Blue Wire Mod Explained
Most voltmeters don't impose any effect on a circuit
because they are in the millions of ohms of resistance
range. If you want to meausure a the voltage of a low
resistance circuit this high resistance voltmeter is
not neccessary, and perhaps that was the design of the
AFC's blue wire mod. I'm not sure what that wire is
supposed to be used for anyway. For the o2 sensor, too
much current flows through the AFC, essentially
putting a load on the o2 sensor itself.

You might see a variation between the pocketlogger and
the afc, but more importantly, you will see a huge
difference if you put a switch on the blue wire. on
Watch the logger, and toggle the switch. Your o2's
will suddenly jump up to where they are supposed to
be. On my 420a NT talon the blue wire dropped the o2's
from .98 to .92 and caused the car to run extremely
rich in closed loop mode (with SAFC zeroed out).

Here is a link to explain the effect of the voltmeter
on a circuit or in this case the blue wire of the
SAFC.

http://physics.bu.edu/py106/notes/Meters.html

 

[Velo_TalonTSI]

Thanks for the info.