Hi folks.

I'm just updating my "Understanding TT 1.8T remapping guide" to reflect recent discussions on KRKTE & particularly KFMIRL/KFMIOP plus some minor editorial updates, corrections, etc. when I came across a possible issue/lack of understanding with respect to LDRXN & LDRXNZK. I'm looking for some assistance in getting to the bottom of it.

I compared LDRXN with LDRXNZK for both BAM & BFV engines and was expecting (perhaps naively) to find LDRXNZK significantly lower across the board. Indeed, a quick look at funktionsrahmen module LDRLMX 3.100 which I have yet to translate confirms: "LDRXNZK: about 15% less than LDRXN". However, this is not the case in either tune. See table below which probably won't render neatly, so jpeg screen capture attached. BAM (225 PS) on the left, BFV (240 PS) on the right.

RPM   LDRXNZK (%)   LDRXN (%)   LDRXNZK (%)   LDRXN (%)
1000   97.0   97.0   99.0   99.0
1720   128.1   128.1   129.8   129.8
2000   139.9   140.6   148.5   148.5
2100   143.6   147.4   154.5   154.5
2200   145.6   146.7   160.5   155.3
2520   148.5   140.8   176.3   166.5
3000   148.2   138.3   176.3   166.5
3520   146.5   140.9   176.3   166.5
4000   148.2   144.0   182.3   166.5
4520   159.4   151.8   188.3   177.0
5000   160.2   151.7   183.0   185.3
5520   157.7   157.7   168.8   171.8
5900   155.8   155.3   162.0   168.8
6000   153.2   153.0   153.8   160.5
6400   142.3   142.3   141.0   148.5

So they look to me to be about the same up to maybe 2,300 rpm, then LDRXNZK is bigger  until 5,300 rpm then smaller, but not by 15%. What is going on? Is it perhaps something simple such as the labelling information has been inadvertently or deliberately swapped around in the BAM engine DAMOS I've got, or is there a more subtle interpretation that I am missing?

Any thoughts, theories, information and even peripheral discussion would be greatly received.

Regards.

Doug

Indeed. So I was expecting approximately 15% lower values in LDRXNZK since I had assumed a lower output would be desirable during continuous knock so LDRXNZK was part of a protection feature. However, that doesn't appear to be the case...?

Doug

That crossed my mind, but I rejected that on two grounds: (a) that it would be more sensible to achieve that through lambda control not charge control and because the ignition timing route is present and valid for these engine variants. I.e. precursors to condition B_kfzk which controls switching between LDRXN and LDRXNZK appear to be normal. I briefly checked KFSWKFZK (ignition angle retardation threshold for switching between ignition angle maps) and found that it was -3.75 degrees crank in all addresses for BAM which appeared reasonable.

I checked the S4 and RS4 DAMOS files to find that LDRXNZK addresses are set to 100 across the board in both. Not something I was expecting. Is that correct? How have you modified yours in your Stage 3 tune Tony?

Since nobody else is jumping in on this thread with good words of wisdom (or even just the answer), I presume that the interrelationships between knock control and charge control are another aspect of ME7.x that is not that well understood?

Doug

In S4s, KFSWKFZK is -96.0 across the board...... Interesting find though. It would be a good idea to maybe think about using it to pull boost on too much timing retard. One approach to meth injection failure protection...

On a general note regarding knock protection... Decreasing the boost is the absolute slowest way to bring an engine away from knocking/pinging conditions as the regulation of boost (in general terms) is very very slow compared to ignition retardation that can be done from one engine revolution to another. Having a boost PID controller trying to adjust the boost level for this purpose in multiple steps takes ages compared to (a) ignition timing change and/or (b) injector timing change (enrichment) that is more of an instant solution to the problem.

In my previous experience (not for ME7 cars), ignition is used first as knocking/pinging protection, secondly injector timing is used and as a last resort the intake air mass is lowered due to the fact that the regulation of the air mass is so much slower than the other options.

There is no better way to cure pinging/knocking than to pull timing, but what fredrik is over looking is that ME7's KR is *ALREADY* pulling timing!

The problem is, EGTs are going to go sky high when you start pulling too much timing. At that point, the best approach is to start adding fuel (see BTS), and third, reduce load (either pull boost, or close thottle).

Adding fuel generally cools the intake charge (especially in forced induction engines)

Yes you are right about that. High performance car and low performance fuel can't go together. I hope someone has a differnt opinion to discuss about the subject, but i strongly beleive that it is all about keeping the same "feel" as you said.