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Discussion and questions related to the course Boost Control
I just watched the boost control plumbing lesson and wanted to ask about another way that I have set up 3 port solenoids in the past.
Rather than using a Tee to join to the solenoid at the NC port and using com to the top wg port, I have used the 3 port solenoid itself as the Tee. I have found that by hooking com to the lower WG port, and NO to the pressure source, even if the solenoid fails, you max at wg pressure. The NC portion then feeds to the top port on the WG. This allows you not only to block off all boost from lifting the valve, but it also diverts the pressure to holding the valve closed via the top hat port. In theory (or at least in my head), this should allow you to run anywhere from spring pressure to max turbo pressure provided the exhaust back pressure does not rise enough to overcome both the spring and the boost it can provide.
I have noticed less duty cycle required to increase the boost.
Is there anything wrong with setting the plumbing up in this way and are there any downsides to using it this way? Perhaps less precise boost control or more difficulty getting a stable boost?
This is how my GDI Genesis Coupe 3.8T is set up (built engine on 93 oct pump gas and 5050 water meth injection). Spring pressure is at 7 psi and max boost is currently 12 psi which puts me at 500 whp with meth injection.
The issue I see with this way of plumbing is you trap the pressure in the NC and top wastegate section. Because the NC port only ever connects to the COM port then how is the pressure released from the top of the wastegate. The only way I can see this is if the solenoid keeps pulsing once off boost and allows the top section to bleed into the bottom section then bleed into the NO/Pressure source.
If you were to do long pulls, back to back pulls, gear changes, antilag or flat shifting it would cause an over boost issue or an increasing boost level since you can release the pressure.
Ah solid point, I would need some way to vent that section of line using another solenoid or something to create another comms to discharge. If that venting issue is resolved, would this give you increased boost range like I'm thinking it is it something that likely won't be noticable?
You would be better off using a 4 port solenoid. This will allow a far bigger range of boost levels. Being able to use a lower wastegate spring but still achieve boost levels 3 or 4 times higher than your spring pressure.
unlike most 3 ports which only allow around 2-2.5 times.