ISC duty cycle max clip

[Turbo4V]

I've noticed recently that the ISCDTY seems to clip at 0.602 (60.2%) when at cold start it is trying to reach DSDRPM (say 1200 RPM) for the first 30 seconds. The ISCDTY stops rising at exactly 0.602 and does not increase even though I can see ISPIBR incrementing up until it reaches it's max clip. So I can't reach DSDRPM if the required air flow exceeds the ISCDTY of 60.2% which per FN8000 is 1.1 PPM. Also the ISCDTY will clip at 0.602 when driving and the DASPOT will continue to rise with RPM but the ISCDTY stops at 60.2% which doesn't provide the required air flow needed to match the DASPOT preposition. So, any thoughts where I should look for what is limiting the ISCDTY?

[decipha]

post the tune file

[Turbo4V]

Here you are, and thank you sir for taking a look.

[Turbo4V]

In the meantime, possibly unrelated but I've always used an ISC valve for an 03/04 Cobra. Not sure where the FN8000 table in the FBGIO stock V8 auto binary came from, but it is quite different from the same table in an AMZ3 03/04 Cobra file. Its always acted OK without using the AMZ3 table so I've left it alone. Just throwing it out there in case it is of any potential relation to the issue.

[Turbo4V]

I was hoping that maybe it was an issue with the older definition I was running, but the ISC clip persists even after downloading the latest 2023 version. Oh well, I will keep searching for the culprit. For now, I just reduced the cold start DRSRPM adders so that it didn't try to exceed 1100 RPM which seems to require just slightly less than 60% ISC on cold starts.