well i found this from a website and it explains it pretty well

A bypass valve (wastegate/regulator) allows the turbo system to develop peak charge-air pressure for maximum engine boost response while eliminating the chance of excessive manifold pressure (overboost) at high speed.

The wastegate is precisely calibrated and opens to direct some exhaust gas flow around the turbine wheel. This limits shaft speed which in turn control boost pressure.


but one question remains. when you have a 9lbs spring and you hit it but you high boost is set at 20 then how do you get high boosted with some exhaust bypassing the turbine wheel. wouldnt that at least make the spool time slower.

 

wow. this is going to be kinda hard to explain. a boost controller uses the boost pressure created by the turbo to fool the wastegate.

ill explain an external wastegate...
there is a vacuum line coming from a pressure source on the manifold that goes to the wastegate. this line feeds the pressure in the manifold/motor to the wastegate. when the pressure in the wastegate matches the pressure of the spring it forces the wastegate valve open a set amount determined by the spring.

a boost controller will force a set amount of pressure on top of the wastegate valve thru a fitting located on the top of the wastegate thus forcing it to stay closed until the pressure below the valve is greater than the pressure above the valve. when u turn the knob on a boost controller it just changes the amount of air being forced into the top of the wastegate.

kinda confusing, hope that helped a little

 

if for nothing else the visual quality on a tial is way nicer then a deltagate.

 

99b16si, you explained it perfect where you described how they work with one another to get what you want.

now say you have a 7psi spring is there a max boost the you can go up to using the boost controller cause of the limitations of the spring, exhaust pressure, and anything else?

 

electronic boost controllers tend to have an upper limit that they can handle (usually indicate the rating). I don't know how they deal with the wastegate once they get there, I guess it depends on who programmed the controller. i would think it should punk out and open the wastegate.

Manual controllers can essentially hold it shut forever.

Either way you should be able to make way more boost then the hard parts can handle.

Boost then is limited by the turbo's match to your setup. Big turbos take longer to spool. If you go too big, you may not be able to spool a turbo to where you want it. Opposite with small ones (except too small, and you get out of the turbo's efficiency and you effectively are super heating the air)

Ideally you get a spring rated the closest to the target boost level you want to run. It usually helps with fluctuation.

Also know, that an indicated spring # number doesn't necessarily tell you how much boost it will equate to. On my truck a 15# spring from Innovative (race gate) nets me about 7-8 psi base. This depends on a lot of things however. I think the biggest in my case is exhaust pressure. The numbers may be closer on other applications.