3K K27-3465 turbine housing issues.
 

I using a K27-3465 with a t3 flanged 18cm2 twin entry exhaust housing, with a total divided short runner manifold and a 45mm wg.
The problem is, even with a 0.3bar wg spring, it boosts over 1bar at 2500rpm in under a sec. at full throttle.
If i gently try to pull the engine to 6000-6500rpm, then I`m easely boosting 1bar at 4500rpm with less then 1/3 throttle.
The turbo is rater big, the ex. turbine has got,

D=3"(76.2mm) d=2.598"(66mm) and 12mm tip hight,
the compressor wheel is

D=3.4"(86.8mm) d=2.26"(57.5mm) and 3.8mm tip hight.

What a/r would this k27 18cm2 housing be?
The engine is a 13bt s5,with 8.5/1 rotors, very early opening and late closing pri. and sec. ports, the rotors are beveled to get a even earlier intake opening.
The ex.ports has been ported 2.5mm upp and 4mm down.

Is it my turbine housing that is to small?
And with the right housing, how much can I expect from this turbo

That 18cm housing would be good for a stock ported motor, with your ports that turbine house and that turbo overall is just way too small. You need to go up to a 2xcm housing at the least if its available. I am also not that familiar with the KKK turbochargers, I know they are made by BorgWarner

Sounds like we have basically the same turbo(except mine is a single entry), response is fast, I have either a 50mm or 60mm wastegate(can't remember which) and I have no problems working at 10psi. What manifold are you using? Perhaps if it's a custom one the wastegate placement isn't correct.

that's fantastic spool.