turbo exhaust housing

hi, i would like to find out if a bigger exhaust housing than the standard would throw the shafts balancing out? ive got a T28 exhaust housing on the T25 turbo. thats all that is different from the T25. thanks

if I'm not mistaken, the flow should be better, as the t28 has a .64 housing instead.
Won't effect balancing at all, as the hole where the wheel sits, is the same diameter.

Only thing is with the .64 it will take slightly longer to get up to boost, that said one might require a wheel to match the housing...

Please excuse my ignorance...but how do you measure the size of the exhaust housing. The reason I ask, is because I know you get different size housings for a T3/T4 turbo for example (I think .90 and .95 or something).

I would like to eliminate some lag on my car (only spools up at 3800rpm on cold days)

i just used a vernier, dont know if it was the correct way of measuring. but i just used it tyo compare the two sizes. i measured the inside diameter

Seems to be a popular misconception that the A/R is a fixed size. Its not its a ratio.
It is measured from the centre of the wheel to the centroid of the passage leading to the wheel.
You can have 2 phyiscally dissimilar exhaust housings with the same A/R.

Its normally cast into the exh housing. There are a few factors influencing turbo spoolup.
Exh wheel size
Exh housing A/R
Compressor wheel size
Exh manifold design
Wastegate design
State of tune
Boost controller

There are a lot of turbo "experts" out there and it seems most of them know just enough to turn your car into a dog. The hot stuff is a T3/T4 no matter the application or engine size and always with the biggest exh wheel and compressor to be found.
The other hotness is to take a tiny little turbo and drive it beyond its design speeds by trying to boost 2 bar from it.

Turbo's are like camshafts, be conservative and you will have a nice smooth power curve and car that is a pleasure to drive.