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Spark adder average of knock sensors


79xd250
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I’ve been tuning my timing table through auf16630 MBT spark on my na fg manual. I’ve data logged it a couple of times now, gone through and looked at where it’s pulling timing and then adjusted the spark table to resemble this. 
the car does feel better and seems to have a much lore linear torque curve but im wondering if the number in that column always mean it’s regarding timing by said amount or can it sometimes to adding timing by said amount? For example at .5 load and 2000rpm -4 means it’s retarding 4 degrees always or can it also mean it’s adding timing at a rate of 4 degrees ? 
 

My logic says it’s retarding and also tells me that where it’s not registering a number in the spark adder column then there is no knocking and it may actually take more timing in these areas. 
 

can anyone confirm this? 

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I have pulled timing from a few areas so far after doing data log runs but I’m curious as I’ve pulled two degrees from a load point after seeing a -2 reading then data logged again and it’s saying - 4 in the same area.  It’s almost as if it’s adding 4 degrees rather then pulling it after I’ve retarded two degrees myself. 
 

seems strange that it would require so much timing to be pulled as in if I pull another 4 degrees that will 6 degrees in total. My previous tuning experience tells me this is strange as it’s a standard engine running factory map which if anything I’d expect to be conservative. 

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The knock sensors pick up false knock and also miss real knock. Use it for safety only, do not attempt to tune MBT with them. You need a professional knock setup to do that. 

Things like broken engine mounts, lose intercooler pipes banging on the motor etc can all cause false knock. 

Log the sensors against each cyl individually to see if it's just one sensor!/cyl, if it is you could have a faulty injector etc. 

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On 9/24/2021 at 2:57 PM, 79xd250 said:

The borderline knock table, is that the limits of what the knock sensors can do at each load/rpm interval when it picks up a knock? 

Borderline knock is what you want to use for adding or taking out timing . Leave the others alone, Ford already did a good job of mbt's. When i tune, providing it looks like the knock sensor is telling the truth ! I Try to keep the spark adder under 1.8 deg of timing that it will take out. The spark adder in my case (14 psi 98 ) always pull timing here there for no real reason. I have a tuner nerd knock sensor and haven't had to use it really, unless I want to find the limits with timing , I guess I wont need it at the moment . Anyway what was the question lol !! Haha , yep just use borderline knock . Regards Graham.

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