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  • Knock Correction Learned Value

    VFTuner Just how important is this value? Two tunes of similar setup, but one has a higher average KCLV than the other by a value of 2. Anything special to consider? Should I make adjustments to low knock direct and port to compensate? There'so real spiking events, just an average of 20 vs 22. The spunkier tune has the lower KCLV, that is why I'm questioning. It seems through general concensus that a higher KCLV average is generally better to have, is this correct?

    Appreciate any insight you have to offer!

  • #2
    Hello, MooseDitty17 . I'm posting over from the 8AR section of the forum, since activity there is next to non-existent. Aside from wanting to know the answers to your questions, I have some related ones as well.

    You mentioned that the spunkier of the two tunes you tried had the lower KCLV value. I've been making non-timing related changes to my tunes and have seen KCLVs ranging from low 10s to low 20s. Oddly, logged ignition timing values remained the same despite the KCLV variances. This goes against the somewhat common knowledge that the ECU adds back the retard it took away from the timing base map depending on the current KCLV value.

    Have you, by any chance, observed this as well? I've only found one reference of this in the IS250 forum of ClubLexus (same guy, here and here) but figured Tacoma folks would likely be paying closer attention to this than most others, given how long you guys have been tuning. Looking forward to your feedback. Cheers

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    • #3
      MooseDitty17
      I have also found that a higher average kclv doesn't mean a tune runs better. A higher kclv will allow it to hit more timing at it quicker but if it sees knock the timing won't keep going up so if it doesn't make that timing up high then the power won't be there.
      From what I have experienced anywhere between 20-22 is good,17-18 is low and doest run as well,19 is ok, 23-25 has a tendency to try to make too much timing too quick and will drive the knock feedback up and in turn the kclv will go back down.
      My current tune runs in the 21 range and runs well.
      For whatever it's worth I run a pretty agressive intake base angle.

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      • #4
        I've had success at controlling KCLV by logging Engine RPM, Absloute load value, Knock F/B and KCLV with OBD Fusion. I then send that file over to excel to sort out all values that are retarding timing below -3. I then edit the values in the spark control high and low knock tables with the amount the ECU is either retarding or advancing timing that is more than 1 degree at the specific RPM and load %. It takes many many runs to get it within the desired range of 20+, but that's how I've done it. Of course this all goes out the window if you change the fuel octane your running.

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        • #5
          Originally posted by Kevinpd325 View Post
          I've had success at controlling KCLV by logging Engine RPM, Absloute load value, Knock F/B and KCLV with OBD Fusion. I then send that file over to excel to sort out all values that are retarding timing below -3. I then edit the values in the spark control high and low knock tables with the amount the ECU is either retarding or advancing timing that is more than 1 degree at the specific RPM and load %. It takes many many runs to get it within the desired range of 20+, but that's how I've done it. Of course this all goes out the window if you change the fuel octane your running.
          That is exactly how i have done it as well

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          • #6
            Originally posted by Kevinpd325 View Post
            I've had success at controlling KCLV by logging Engine RPM, Absloute load value, Knock F/B and KCLV with OBD Fusion. I then send that file over to excel to sort out all values that are retarding timing below -3. I then edit the values in the spark control high and low knock tables with the amount the ECU is either retarding or advancing timing that is more than 1 degree at the specific RPM and load %. It takes many many runs to get it within the desired range of 20+, but that's how I've done it. Of course this all goes out the window if you change the fuel octane your running.
            Did you find the timing values in logs corresponding to exact values in your high, low, or base plus retard tables? In my platform, the logged ignition timing value is sometimes off by 3 to 5 degrees after corrections (Logged ignition timing value - KCLV - KFB - 3) yet sometimes spot on.

            Did you ever have to modify the base and retard tables, or were all your changes confined to the high and low knock tables?
            How did you decide which of the high and low tables to change?
            Or did you always change both at the same time? Thanks!
            Last edited by ChezGKY; 07-14-2021, 08:25 AM.

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            • #7
              Originally posted by ChezGKY View Post

              Did you find the timing values in logs corresponding to exact values in your high, low, or base plus retard tables? In my platform, the logged ignition timing value is sometimes off by 3 to 5 degrees after corrections (Logged ignition timing value - KCLV - KFB - 3) yet sometimes spot on.

              Did you ever have to modify the base and retard tables, or were all your changes confined to the high and low knock tables?
              How did you decide which of the high and low tables to change?
              Or did you always change both at the same time? Thanks!
              I originally started with the low knock table, but i ended up returning it to stock and went to high knock only.

              The base table plus retard is max.

              There are more factors that it uses to determine how much to add.

              The timing will fall between Low knock and base depending on knock learn and knock feedback. Every tank of fuel can change how it reacts.

              I do have one area that needed some additional timing out of the base table (done through base retard) but all my other changes were in the high knock table.

              I'm on 87 octane now (started with 90) but keep a kclv at 20 and knock fb between -2 and-5. The occasional spike does still happen but it is so short that it's normal and adjusts as necessary.

              Previously i had periods of consistent -6 and-7 where my kclv would tank and i could feel the truck holding back during acceleration

              I also did adjustment to the ignition efficiency table under high load to help prevent aggressive timing add at low rpm and adjusted throttle efficiency inverse to that to request more throttle instead. (The major dip and hump in the .8 table, very slightly)

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              • #8
                Originally posted by 92ehatch View Post

                I originally started with the low knock table, but i ended up returning it to stock and went to high knock only.

                The base table plus retard is max.

                There are more factors that it uses to determine how much to add.

                The timing will fall between Low knock and base depending on knock learn and knock feedback. Every tank of fuel can change how it reacts.

                I do have one area that needed some additional timing out of the base table (done through base retard) but all my other changes were in the high knock table.

                I'm on 87 octane now (started with 90) but keep a kclv at 20 and knock fb between -2 and-5. The occasional spike does still happen but it is so short that it's normal and adjusts as necessary.

                Previously i had periods of consistent -6 and-7 where my kclv would tank and i could feel the truck holding back during acceleration

                I also did adjustment to the ignition efficiency table under high load to help prevent aggressive timing add at low rpm and adjusted throttle efficiency inverse to that to request more throttle instead. (The major dip and hump in the .8 table, very slightly)
                Huge thanks for the very thorough reply. It's good to have something new to explore on my 8AR platform. I was toying with the base table retard table to try to get KCLV higher than 10 but gave up when nothing was happening after my changes. It turns out I was editing the wrong table. It's also reassuring to hear that your ignition timing falls somewhere between one of the knock tables and base and not always to an exact value in one of the tables.

                Do the low knock and high knock tables correspond to certain KCLV ranges? Was your decision to edit just high knock a result of already being in a high KCLV range to start with? (My understanding of this may be flawed. Please correct if so.)

                For the one area you edited through base retard: did you do so after seeing logged ignition timing exactly at base table - retard + kclv + kfb - 3 ie. max?

                As for ignition efficiency - I don't think I'm ready to adjust that table yet for my NX. Engine load on our table goes up to 458.333. Table values, on the other hand, go to 1000. Throttle efficiency inverse doesn't seem to exist in my ECU ID.

                Once again, thanks for the patience and thorough replies.

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                • #9
                  I'm not 100% sure of anything, but i took out of the base retard based on the fact my ignition timing at that knock instance was higher than the high knock table and close to the base table. I also asked Matt about it.

                  I also only adjust by .5 degrees at a time usually.

                  As for for ignition efficiency and throttle efficiency, the values in those tables mean nothing to be, i just smoothed some based on information provided by Matt a long time ago regarding how that table works.

                  Comment


                  • #10
                    I just flashed my truck back to stock for some testing. After driving around a bit and monitoring, KCLV is hovering around 23.8 on 91 octane. Just for reference. I'm going to be driving it a little over 100 miles tomorrow. I'll report back with where it ends up.

                    Comment


                    • #11
                      Originally posted by Kevinpd325 View Post
                      I just flashed my truck back to stock for some testing. After driving around a bit and monitoring, KCLV is hovering around 23.8 on 91 octane. Just for reference. I'm going to be driving it a little over 100 miles tomorrow. I'll report back with where it ends up.
                      On the stock tune it will probably stay around 23 with 91. That is what mine was when i was on stock ignition settings. The problem i had was heavy knock when the ambient air is warmer.

                      In the morning my learn value would get to 25 or 26.

                      In the afternoon my drives home sucked in the warmer air and the truck would knock for a bit, the kclv would tank.

                      I only made the adjustments for consistency between drives.

                      If i ran 93 octane on a regular tune, it was fine. If i ran 93 on the premium tune it was worse.

                      In my opinion, the truck should run premium on stock.

                      I don't want to purchase premium, but i want smooth operation, so i started adjusting, even if it costs me a little torque (which i haven't noticed any losses)

                      Comment


                      • #12
                        Originally posted by 92ehatch View Post

                        On the stock tune it will probably stay around 23 with 91. That is what mine was when i was on stock ignition settings. The problem i had was heavy knock when the ambient air is warmer.

                        In the morning my learn value would get to 25 or 26.

                        In the afternoon my drives home sucked in the warmer air and the truck would knock for a bit, the kclv would tank.

                        I only made the adjustments for consistency between drives.

                        If i ran 93 octane on a regular tune, it was fine. If i ran 93 on the premium tune it was worse.

                        In my opinion, the truck should run premium on stock.

                        I don't want to purchase premium, but i want smooth operation, so i started adjusting, even if it costs me a little torque (which i haven't noticed any losses)
                        I agree, the high compression motor really begs for premium fuel. When I run premium on 2.0 ignition regular map I get around 25-27 kclv and never under 23. With regular, I'll get down to 15 in the mountains where I'm chugging along in overdrive. I don't really have the time or will power to play with ignition maps to keep it consistent with regular.

                        Comment


                        • #13
                          Originally posted by Chadr7858 View Post

                          I agree, the high compression motor really begs for premium fuel. When I run premium on 2.0 ignition regular map I get around 25-27 kclv and never under 23. With regular, I'll get down to 15 in the mountains where I'm chugging along in overdrive. I don't really have the time or will power to play with ignition maps to keep it consistent with regular.
                          Same, got my truck timed and knock adjusted pretty well for premium. Range from 23-26 kclv. Tried throwing in some regular just to get it to the dealership for my fuel pump recall. Saw 11-15 during that. After going weeks and weeks dialing in the knock for premium, I was like... nah. Wasn't even going to try. I'm sure part of it is I have it timed the same as the Lexus IS350, which runs solely on premium.

                          Comment


                          • #14
                            Originally posted by ChezGKY View Post

                            Did you find the timing values in logs corresponding to exact values in your high, low, or base plus retard tables? In my platform, the logged ignition timing value is sometimes off by 3 to 5 degrees after corrections (Logged ignition timing value - KCLV - KFB - 3) yet sometimes spot on.

                            Did you ever have to modify the base and retard tables, or were all your changes confined to the high and low knock tables?
                            How did you decide which of the high and low tables to change?
                            Or did you always change both at the same time? Thanks!
                            Kind of an old thread, but figured it was worth revisiting since I've been super busy with development. I've not found a need to adjust base retard as the high and low maps have been my main focus for knock corrections. Started with any values that were -6 or worse and worked backwards eventually correcting for any prolonged -5 that were not just spikes. Brought both high and low tables down the same value simultaneously so as to keep them offset. The result after many runs and logs has been consistent 30+ KCLV with only occasional -4 spikes on both 91 and 87 octane.

                            Comment


                            • #15
                              Originally posted by Kevinpd325 View Post

                              Kind of an old thread, but figured it was worth revisiting since I've been super busy with development. I've not found a need to adjust base retard as the high and low maps have been my main focus for knock corrections. Started with any values that were -6 or worse and worked backwards eventually correcting for any prolonged -5 that were not just spikes. Brought both high and low tables down the same value simultaneously so as to keep them offset. The result after many runs and logs has been consistent 30+ KCLV with only occasional -4 spikes on both 91 and 87 octane.
                              Thanks for the updates. I haven't made much progress on the 8AR turbo, honestly, since I've been A. swamped with work and B. clueless whether I should adjust high or low tables. One thing's for certain - adjusting base and base retard tables did nothing for my KCLV.

                              Simultaneous adjustment to keep the offset and save a lot of time sounds very attractive to me. I'll try it out soon. Have you found the opportunity to add timing on certain cells? Say, after seeing KFB hit -2 or even -1? If so, did simultaneous adjustment of the high and low tables still work out for you?

                              Thanks again!

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