Fuel cut but no overboost

[MMSSPP66]

Having all kinds of headaches. Installed high pressure internals, all went well. 2 months later notice idle FP of 190-220, would build slowly under part throttle but die under heavy load. Researched online figured out it was the relief valve. Replaced with a Pt-p unit. Fuel pressure now looked great, 400+ at idle and whatever I command at WOT 1800-2000. I'm getting fuel cut now however, at first would happen somewhat randomly, especially in hard first gear pulls. Checked for boost leaks etc. Got slightly better. Then I put FP settings in ATR back to stock levels and the issue is *almost* gone. Now I only get it at around 6300 rpm. I have no overboost and my AFR's look good until about 1/4 second before the cut. Drops from 11.8 to 11.2 or lower then I have the cut. I was still suspecting a boost leak but my boost is very close to target all through the rpm range I attached a log, you can see at 6.96 seconds it starts to richen then cuts at 7.12 seconds, 6302rpm. Any help would be greatly appreciated.

 

[MMSSPP66]

I figured I'd post my findings to help anyone in the future who may have this issue. Braden from Cobb, via the Cobb forums, said it seemed my fuel pressure was experiencing a sort of runaway. the ECU and tune desperately tries to control it, and then actually loses the exact reading since it wants 1700psi (or whatever setting) but FP was ramping to 2000 or so, so it cuts not knowing if there is actually too LITTLE fuel or whats going on. I only experienced this after install of the PT-P upgraded Rail valve which apparently for my modest/moderate system does its job a bit too well. He (John) personally built me maps that tapered the FP down in the upper RPM range, and it helped slightly, but I still experienced a cut. Braden suggested that the only way to combat it was to set FP settings to build slowly rather than hit full targets sooner in the RPM range. This also helped a bit. So I ended up combining the two ideas, ramping it to a peak and then tapering it and it helped even more. I still get a slight cut/bog at 6400 rpm or so because the pressure still wants to build. I set my rev limiter to 6300 and its running like a champ. Not like my KO4 has anything left to give past 6k-ish anyways. Hope this can help someone in the future.

 

[speed666]

thanks for the input!!!