They are also very weak 6# actuators... and there is not much that can be ported since the flapper is only 26mm (can maybe get 3mm out of it). Aside from that there are several who basically locked the actuators by shoving 4-5 washers behind them and retain boost falloff to the same degree as before... so I am not yet convinced that is the ONLY thing causing falloff; I have some concerns about the pressure source being so far upstream at the y-pipe (IC losses??) rather than direcly on the comp housing (like alot of other turbos volvos/wrx/etc) along with possiblity of controller insufficiencies. Also there is some advantages to having a bigger flapper hole... better flow out of the turbine housig if the compressor is not maxxed out.
That said, I still would like to see the calcs for a 20mm (TD04 stock) and 23mm (TD04 ported) hole... and even a 27mm (TD04 modified flapper/ported) hole.
Thanks,
Rob
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Originally Posted by Multiades
Honestly, I'd say you DON'T want to port the stock TD04 flapper. TD04 turbine backpressure will be very high, and every TD04 I've ever experienced has had boost falloff already. There's no concern of boost creep if it can't help but drop pressure to redline already.
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