I've compared several srt-4 files I've found online to one I pulled last week. They all seem to have different values in the long term max retard table.
Is this table just a read of the current long term max retard trims, or is it a table to set the limit of the max long term knock retard?
I pulled the battery, and waited about 15 min. When I re read the ecu it still had the same numbers.
Thanks,
I usually zero that table out. Its a learned knock so as long as your calibration is good, you shouldn't need it.
Jaime
If the tune is correct you never need to touch the LT KR table. Its there for a reason and as a fail-safe, it would be irresponsible to disable it.
That's not true in all cases and the short term KR is more than capable of keeping the motor safe under most conditions. Forced induction applications I'll usually keep it populated, but NA cars is a cases by case for me.Originally Posted by duster360
Jaime
Ok, thanks.
Will it advance to zero by itself if no knock present?
Those are limit values, meaning that if a particular cell has a value of 6, the adaptive Long Term Knock Retard will not be able to retard timing beyond 6* for that given load/RPM cell.
On a freshly wiped PCM (meaning all adaptive trims reset), the PCM starts out with everything 0'd out by way of trims, and immediately starts populating the Trims upon 1st start-up/closed loop operation. Ignition timing "Knock-Retard" trims usually won't start pulling timing back until you get to a higher load value and the PCM senses knock, and even at that, it's not likely going to pull timing down during idle/light load cruising, unless the octane of the fuel being used is really low.
It's not that a freshly wiped PCM starts out by pulling 6* in that load cell, then eventually reverts back to 0 over time. It's the contrary. It starts out at 0, then begins retarding the timing if it learns that it needs to.
Last edited by B00STJUNKY; 10-15-2014 at 06:46 PM.
I've seen more than a few Srt-4 max out ST KR at 6.0 degrees, so its nice to have LTKR there to back it up. It just makes no sense whatsoever to limit the PCM's potential to save the engine.
Wouldn't it make more sense to give the PCM more tools and more capability to implement fail safes than less? On more troublesome builds I make the Knock sensor sensitive and bump up both LT and ST Knock clips. Better safe and stupid, right?
While doing this in the GM and Ford cars is appropriate I personally know the entire theory and logic behind the Chrysler knock sensor algorithm and if you use it correctly it is EXTREMELY accurate.
Couldn't have said it better myself
GM knock strategy is nothing like this so it would not be "appropriate" at all. They use a low octane table and a learn-up/learn-down logic. If it is so accurate, then why do nearly all of the Hemi calibrations suffer from terrible false knock from the factory? I don't doubt the knock detection is capable of being very accurate, if calibrated properly, but for the Hemi platforms they got it wrong. Maybe on purpose, but still wrong.
Now, most of my Dodge/Chrysler calibration experience center around the HEMI and V6 engines so I can't speak to the accuracy of the SRT-4 knock calibration. Sounds like it's much better than the V8's and I will say that the V6 is probably somewhere in the middle.
The Gen III LS knock calibration is still, by far, the most accurately calibrated system I've dealt with to date.
Jaime
Thanks guys for the input. So what is the official definition of the table?
A limit or a learned value?
It's a limit for LT knock retard.
Jaime
Thanks!
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