So the small turbo is what I currently have.
It kicks in around 2800 rpms compared to 2500 rpms of the stock K04
When are you going to kill it's boost and have the larger turbo kick in?
it depends bro.
Back pressure of the system will really be the determining factor.
Kevin Jewer with the DSM compound turbo set-up (my guru) for example sets his small turbo's wg at 19psi. It spools at 19psi. But his big tubo's back pressure (9 psi) causes the small turbo to boost at 28psi. So basically, once both turbos are spooling together via compound set-up, the small turbo will eventually reach 28psi.
so to answer your question, I will only be using a 14psi spring on my 60mm wg for my small turbo. If my big turbo has a back pressure of 10psi, it will cause my small turbo to boost at 24psi even though I set the wg at 14psi.
If the big turbo produces more back pressure, the small turbo will produce more boost thus making it closer to a Pressure Ratio of 2:1
but at the beginning once the small turbo spools at 14psi....it will start releasing exhaust gases (via 60mm wg) to the big turbo. Once the big turbo starts producing boost and starts cooking.......back pressure will be created, causing the small turbo to be around 24psi.
the back pressure will greatly be affected by the system's air flow characteristics, total air flow....and etc......
I'll be learning more about this once we start tuning. So we'll see what happens