finnigan001 Posted February 11, 2019 Share Posted February 11, 2019 HI all, Just wanting to pick peoples brains over an issue i've been trying to sort for awhile. I have an fg mk1, 12psi actuator on a gt3576 with 37mm port, 4inch dump and high flow cat with a full exhaust. For a long time now i've been trying to tune out 'overboosting or boost spikes' on gear changes , mainly 1-2 and 2-3, with varying success. I'm running 16psi to 4750 which tapers down to 10psi at 6000rpm. By doing this i've managed to keep the spike between gears to about 18.5-20psi. Any higher than that causes boost cut on gear change. But to allow this to happen i have set auF0296 ( Overboost required for open loop duty cycle ) to -22hg and all the cells in the WG DC table the gear change may fall into to 0.1DC(completely open). I've set au0296, to -22hg as it seems on gear change it uses the cell in the previous when calculating an error. eg. 2nd gear @ 6000rpm, has commanded 10psi. So on change to 3rd if it hits 10psi +11psi error then it will boost cut. It wont calculate it on the cell it is changing into. ie 3rd 3500rpm (16psi + 11psi). So to the not so good. If using manual mode and changing gears earlier at higher than 10psi. eg 15-16psi @ 4000-5000rpm. will cause the boost to spike higher on changing gears than just running through the gears in perf mode and letting the boost taper off. Boost cut happens and it all gets a bit nasty. This occurs regardless of how open the wastegate is. I command it to open all the way but it seems like its not fast enough to vent between gears. With my port job i don't suffer any boost creep or inability to control boost other than on gear change. Should i be worried about how high boost gets on gear change? Is there something i'm not changing in the tune i should be looking at? I feel like if just up the error and overboost values to -30hg etc than i wont get boost cut on gear changes but then i would also not have any protection in gear(able to hit ~30psi). Although this is unlikely to happen. Any pointers / suggestions welcome. Any one experiment with this 'issue'? Cheers guys. Quote Link to comment Share on other sites More sharing options...
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