This.

Set the req boost where you want it, then tune the PID.


You should be able to do it all with KFKHFM and KRKTE.

You can't really fix "spikes" per se, only basic trends. If you are seeing spikes, there are likely other issues.


I think you are confusing req and actual. KFLDHBN limits req boost. Devation is the difference between req and actual. KFLDHBN cannot limit actual, only request.


The PID has no effect on request. The PID is there to make actual match request. You need to research PIDs and control systems. Request is the set point, actual is the measurement.


Never do a "mean time" fix. Fix the underlying problem.

KFLDHBN does not throttle cut anything. It affects specified and thus requested load.

The throttle cut is due to actual staying over requested for an extended period of time.

No, it may not have been a coincidence, you probably just exceeded requested load.
Please, when you tune understand why you do things and how they are done. Don't just try changing maps for kicks and seeing what happens.
This is best way of wasting lots of time and getting nowhere... especially if the documentation for the ECU is readily available.

KFLDHBN  makes up part of the requested load calculation.

When actual load goes over requested then the ECU can go as far to cut the throttle to bring actual load back in line with requested.

So....

If your actual boost goes over KFLDHBN then you ~can get a throttle cut, but this doesnt mean to say that KFLDHBN controls if you get a throttle cut or not.

Based on your statements, I figured that this was the case, yes.
This map only limits specified corrected via rlmax. Furthermore, this map is there to protect the turbos from overspinning. It is not there to protect your "block" as you put it.
It also has as little or as much to do with throttle cut as any other map that affects the requested load calculation.

The fact that you are using it as you are shows a lack of understanding for this map. If you want to limit maximum cylinder pressure for your block, you should use LDRXN together with KFTARX. Boost is not what puts pressure on your block, cylinder filling and combustion circumstances do.
KFLDHBN is for the turbos alone. This is because cylinder pressure will rise and 1.5 bar in -10C ambient and 30C ambient will put very different strain on the mechanical components in the engine, but it will not do all that much for the turbos. In case of the turbos - the main problem is altitude and overspinning them there.

So in closing - yes, I do not think you are using it correctly.
It's your car, your tune, and you can do what you want with it, but saying that KFLDHBN is some sort of hard boost limit that gives throttle cut is incorrect. In fact, KFLDHBN should never cause throttle cut, it will just make the ECU request less load in some circumstances. If it is causing a cut, then your PID is configured incorrectly or the linearization tables are off.

Look at the LDRLMX section in the FDEF and you will understand what I mean.