Discussion and questions related to the course Boost Control
I have a very weird issue that I am struggling to diagnose. Engine has been recently rebuilt, previously it made 30psi with a 15psi wastegate spring. Now I am struggling to make anything above 15psi with the EBC MAC valve. Previously I had it setup just bleeding off boost to the wastegate bottom port, but that was now not allowing boost to increase, so I've recently swapped in a new EBC MAC valve and plumbed it with full boost signal going to the bottom port and the EBC controlling a boost feed to the top port. I did make a little more boost with the EBC at 80% DC (only up from 15 to 17 psi but more of a spike than a solid hold of boost).
With nothing hooked up to the wastegate top or bottom ports, it will make 25+psi (not sure if it is holding or spiking though, too scared to try on the road). Same goes with a manual boost controller in place of the EBC.
I've tried different DC % and frequencies for the EBC, from 19hz to 33hz with little to no change. 100% DC on the EBC it theory should have it reach the 25+psi, but this is not the case. I've tested at at 0%DC or turned off, no boost reaches the top port. At 100%DC, full boost reaches the top port.
I'm going to bench test again with a compressor tonight, but I am at a loss. I'm now starting to think about things like the BOV opening at higher boost (it's an older synchronic), or a boost leak, or even the wastegate ring being missing. Problem is none of these make sense when I've proven it can make more boost with a manual boost controller or with no boos signals connected to the wastegate