Hey guys... I'm in the process of developing a new timing map and I'm wondering about the function of the 4 low octane tables in Tunercats. My theory about the low octane tables is that the PCM applies these multipliers to areas it has seen knock in the past regardless of whether it is currently being detected. Is this correct? If not, how exactly do they work?

A little background - I get false knock consistently around 3k from the headers and/or valvetrain....same amount of KR with everything from 8 degrees timing to 30+. Always at the same rpm - 3000 - 3200. For my testing I'll be zeroing out the Max KR vs. RPM table in that area and leaving the rest it alone in the hope of only detecting real knock. To only see real knock, should I zero out all 4 low octane tables as well? I'm trying to use the knock sensor to detect real knock in real-time and not have to wonder if the readings are historical or otherwise false...if there's a better way to accomplish this I'm all ears.

Appreciate any guidance....I still pretty new to PCM tuning.

 

Casey, I have always wondered what activates the low octane tables myself, I also had a false knock retard in a 500 RPM range before and after my cam/rocker installation (PE mode @ 3700-4200 RPM) that I was trying to isolate and fix with timing. I do use 92 octane so I just ignored the low octane tables. I blew a lot of time playing w/backing off timing, looking logs, etc. and finally spent $40.00 on an LT4 KM that cleared the knock. You could try " http://www.monodax.com/forums/tunerc...ware-software/ " for an answer on the octane tables, some of the posters there are really into how the s/w thinks. IMO your knock in only a 200 RPM range that does not change when you retard timing way down looks false, have you tried the LT4 KM.

 

Thanks for the reply.... Glad to hear I'm not the only one with knock issues at a specific rpm. I'm familiar with the Monodax site and posted the same question there along with some others but no luck on responses so far....seems to be a pretty slow forum.
I've tried the LT4 KM as well as stock OBDI and OBDII modules...they all behave exactly the same for me. Gave up on that avenue a long time ago and just left the LT4 module in there.
I went ahead and zero'd out the low octane tables which didn't really change anything...still have the same knock behavior so I'm assuming it's "detected" knock versus "expected" knock....pretty sure it's false though. I'm still playing with the timing curve to get rid of real knock in the 1600-2400 range (mail order tune had WAY too much timing in this area) and once I'm done I think I'll just zero the knock fast attack table in the 3200 range and call it a day.