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Quick Info on My Setup
MKIV Supra
2JZ-GTE
Single turbo: BW EFR 8474
Artec twin-scroll manifold
Two Turbosmart 45mm external wastegates
I’m considering two different approaches for boost control and would like feedback on realistic boost ranges relative to spring pressure.
Option 1: 3-Port MAC ValveI’d run a 3-port MAC solenoid with both wastegates teed off after the boost controller.
With this method, what’s the practical boost range above spring pressure?
For example, if I use a 14 psi spring, how much higher could I reliably push boost?
Option 2: 4-Port MAC ValveThe other option is a 4-port MAC solenoid.
Same question here: with a 14 psi spring, what kind of upper boost limit is realistic?
I understand the 4-port provides less resolution but potentially more range—that tradeoff might be worth it.
Ideal Goal:
Base boost: 12–14 psi
Adjustable up to ~33 psi (turbo max)
Ability to fine-tune anywhere in between
I’m open to suggestions or alternative setups. Also I run open loop boost control with a feedforward table if that matters.
Thanks!
Here is very good explanation of what can be expected from both methods in terms of maximum boost level...
https://www.enginebasics.com/Advanced%20Engine%20Tuning/3%20port%204%20port%20boost.html
