t4 vs t3 t4 hybrid

[RETed]

Turbine A/R dictates your power band - generally speaking.

You can just drop down one turbine A/R size, and that will induce the turbo to boost faster.

The problem is that if you drop the turbine A/R too much, you start to choke power, and you lose top-end power.
It's a delicate balance of sizing the turbine A/R.

In general for a 13B using a T4 sized turbo is to run an around around 1.00.

At this point, it's probably the least hassle just to swap the turbine housing to a smaller A/R.
No need to mess with the wheel or any other part of the turbo.
You might need to readjust the intercooler pipes, as the turbo position will be slightly different.

Side note about clipping the turbine wheel...
This is primarily to increase flow through the turbine section and to minimize the turbo overspooling - in essence, it kills the efficiency of the turbo.
This is really a band-aid fix for a turbo (i.e. turbine) that's not sized properly.
Bottom line: if you size the turbo properly, there is no need to clip the turbine wheel.

BB centers - I'm talking primarily Garrett units - are expensive.
It's expensive to fix if something goes wrong.
Last time I checked, a Garrett GT-series BB CHRA starts at $1,000 and goes up.
Garrett does not sell the individual parts.
You have to buy the entire CHRA.
(If you don't know what "CHRA" is, it's Center Housing and Rotating Assembly - it's the turbo minus the turbine and compressor housing.)
In general, the BB center will give you only about 500RPM faster spool versus a non-BB center when the turbo is sized properly.
The Turbonetics BB centers are CRAP in my book.


-Ted