If you want to make 12psi on the SOS kit those 12 psi will be @ redline.

With a wastegate you can run fro example a 20 psi pulley and cap it to 12 psi in the rpm range by releasing pressure. If the 20 psi pulley give you 12 psi around 5000 rpm, with good boost control you will be able to have 12 psi from 5000 to 9000 which will give you better mid range than if you have 12 psi @ redline, boost will ramp up faster in the lower rpms too.

The big trade off is 20 psi warm air entering in the engine so cooling have to be upgraded, a second tensionner is a good idea too.

 

any concerns about wastegate failure causing it to go higher than the 12 psi and causing issues?

 

Always. Boost creep is no joke, but can be easily monitored. A simple boost gauge is step one; tying in that boost signal to a warning system or failsafe mode if excess boost is observed is better.

 

Also, since the wastegate has a smaller spring than your target boost, you'll always be capped at that level. Example, use a 12 PSI spring to cap your boost at 14 PSI. If anything failed, the spring would open the wastegate at 12 psi. Caveat, if the wastegate valve itself binded for some reason then you're screwed. This is pretty unlikely, particularly for a supercharged application as the air it's exerting is clean & filtered vs in a turbo application where its dirty exhaust gas.

 

this is a great idea, impressive stuff

 

I want to see a dyno sheet of this setup!

 

Another example on S2ki

 

ahh i see, so more midrange response with smaller pulleys.Thanks! im not at that level yet. still on the 4.2" standard pulley.

 

Sorry I didn't know people were still watching this thread.

So I attempted to run e85 but ran out of pump on the Dyno around 17psi. I rewired the stock line to 12awg wire and my fuel pressure jumped from 65 base to 100+ psi when I returned it to 65psi my A/F was 10 flat. So I should be good to continue my tune this weekend.

When I strap it back on I will get everyone a Dyno plot.

Also the car is night and day from my older 360whp....omfg its fast.

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That and the blower bearings will wear out faster due to the added heat and revolutions. If you ask me, its a neat idea that can work if properly executed, but why do it? Its a big waste of energy the blower is evacuating, I say let the motor see the 20psi and get all the same mid range benefits as current but a lot more top end. The motor can take it so why not.