DFCO Disable RPM Rate?

[xrulingh]

Searched, but cannot get a grip on exactly what Disable RPM Rate does for DFCO.
There are settings for both Disable RPM and Disable RPM Rate

Enable RPM set at 1150. DFCO is allowed above this RPM.
Disable RPM is set at 1050. Below this RPM, DFCO is disabled.
Disable RPM Rate is set at 300 (factory). Above this RPM, DFCO is disabled.

Edited to create a new question ..

It seems that with Disable RPM Rate set at 300, DFCO is effectively always disabled, or does the Enable RPM setting override this? Meaning that DFCO is only disabled between 300 and 1150 RPM?
I really don't understand why Disable RPM Rate is needed - it seems redundant considering the functions of Enable RPM and Disable RPM.

[07GTS]

i havnt played with it but to me it looks like its a rate of rpm per time, purely a guess but might be if it decelerates within 300rpm per second it will stay enabled but if it exceeds that it will disable

[grubinski]

That seems like a good guess ... but what controller/engine is this on? I have none of that in my circa '09 E67 tune.

[07GTS]

i noticed it in my e38 with the latest updates, not sure on the e67

[xrulingh]

that seems like a good guess ... But what controller/engine is this on? I have none of that in my circa '09 e67 tune.

e38

[xrulingh]

i havnt played with it but to me it looks like its a rate of rpm per time, purely a guess but might be if it decelerates within 300rpm per second it will stay enabled but if it exceeds that it will disable

Maybe! Wish we could find an authoritative source for confirmation.

[07GTS]

mine is set to 400rpm factory sounds like the higher rpm will keep it enabled longer (within threshold)

[NotSure]

I have played with Disable RPM Rate as well, and it seems to be an actual max rpm of where DFCO can occur. My stock chart was set at 1800 and I did not see DFCO above that point. I have since raised it to just below the max allowed of 4096 rpm and it is kicking in near 4000 rpm now. So maybe the definition/naming is misleading. The word "rate" is redundant, in other words. RPM is a "rate" of measure in itself. Think of it as an RPM ceiling for DFCO operation.

I have also had positive results in greatly reducing the DFCO Entry Spark/Blend Time, especially at the higher rpms, as this seems to be delaying DFCO activation. I believe it blends into the spark of your settings in the DFCO Entry Spark table, and THEN allows DFCO to activate.

Another thing to note, my injector pw never goes to 0 in the scanner, only to the min pulse of 0.7. I have to log DFCO Yes/No to see for sure if it is activated, which is confirmed in the wideband pegging lean right afterwards. Before DFCO activates, even with inj pulse at the min, it just goes richer and richer.

[daktah]

id also like an explanation on this, and if it is indeed an rpm ceiling a way to disable it or a higher limit to effectively disable it.

[TRStech]

I have played with Disable RPM Rate as well, and it seems to be an actual max rpm of where DFCO can occur. My stock chart was set at 1800 and I did not see DFCO above that point. I have since raised it to just below the max allowed of 4096 rpm and it is kicking in near 4000 rpm now. So maybe the definition/naming is misleading. The word "rate" is redundant, in other words. RPM is a "rate" of measure in itself. Think of it as an RPM ceiling for DFCO operation.

I have also had positive results in greatly reducing the DFCO Entry Spark/Blend Time, especially at the higher rpms, as this seems to be delaying DFCO activation. I believe it blends into the spark of your settings in the DFCO Entry Spark table, and THEN allows DFCO to activate.

Another thing to note, my injector pw never goes to 0 in the scanner, only to the min pulse of 0.7. I have to log DFCO Yes/No to see for sure if it is activated, which is confirmed in the wideband pegging lean right afterwards. Before DFCO activates, even with inj pulse at the min, it just goes richer and richer.

Im not sure if I can agree with this assumption. Im also dealing with thtis value currently, since Im seeing strange beahavior under decel. Im running the engine in a lighter car with and with a lighter flywheel. I see DFCO activating and deactivating during some coast conditions. It seems, that if a specific rpm reduction (or change?) per time is exceeded, the DFCO stops operation what results directly in very high STFT and a massive rich condition.

I dont have an answer to the initial question, but in my eyes, raising the rpm rate doent result in higher kick in of DFCO cause its working like a clipping value. I would say that it kicks in more early simply since the rpm drop per time is natuarly higher, the higher the rpm of the engine is.

If anyone has a confirmed answer to this, I would highly appriciate since I need to get rid of this STFT spikes and the rich condition under decel.

[NotSure]

You also have airmass enable/disable values in the cal. You may be going in and out of those threshholds when you see DFCO turning on and off on a decel. ECM 12252 and 12253.

[TRStech]

I unfortunately dont have this PID logged on the files I see this happen, but based on both MAF and VE airmass readings vs rpm, the cyl airmass should be well below the set boundrys. (based on a manual calculation for cyl airmass)

I meanwhile might have some other findings. Geting on the brake seems also to force a exit from DFCO. As well, the STFT spikes and rich condition might not be completely bound to the DFCO. I meanwhile have the idea that this could be caused by a catalyst learning procedure for emission DTC. I wrote a post in another thread concerning this topic. https://forum.hptuners.com/showthrea...l=1#post653682

See attached a log showing the phenomenon. It occures 3 times here. Most obvious starting at arround 4:10 in this log.

20210604_V0.56_MAF+GMVE_Step3.hpl