Your welcome!
More on turbo tech:
Trim basically adjusts the sweet spot of the turbo, it changes the response and overall output.
There are different wheel sizes and trims. 30, 40, 50, "super" 60 denote the size of the wheel in MM.
Turbine trims N, O, P, Q etc. In which the vanes/diffuser is shaped different but I wont get into that.
People like to adjust the trim in a effort to increase output of a turbo as a bandaid, but it can be a big no no!
The A/R ratio is a function of the distance from the turbine to the housing described in a ratio. The larger the ratio the farther the turbine is from the housing. This gives the turbo slightly slower response in the lower rpms and makes it more efficient in the higher rpms. And vice versa...
A cheap way to make a small turbo more efficient is to give it a larger ratio, this saves you the money of replacing the whole thing and usually gives you a power boost. Guys in the turbo MR2 camp often replace the compressor housing with one from T4 (it has a proprietary Toyota CT26, similar to a T3) and make a good amount of power.
But trim can only go so far, a small T28 at full boost can spin in upwards of 100k rpm! At that speed the air is being sonically whipped which makes the charge temp soar further lowering efficiency. In the same config a T4e would spin at apprx 45k rpm and even at the lower rpms the big fan on the t4e would push more air then than T28.
There is a huge misconception that you have to have a small turbo in order to have a responsive turbo. With advanced technology its now possible to make a big t4 as responsive as a t28. Ball bearings are more and more popular today, but most people don't know that there are two versions in use. Turbonetics uses a single ball bearing (I forget on which side of the turbo its on, probably on the compressor side) and HKS has a full ball-bearing center section. Both which give you better response than the standard thrust bushing, but some guys swear that the single sided ball bearing lasts longer than the dual sided unit.
Extrude hone now being used by most of the racers that are doing single digit Honda runs. Lisa Kubo was one of the first, I think she gained like 50hp by just having the turbine housing honed. Mike Kojima is making 320+whp out of his 200SX with a stock 4cyl engine. I was there for the dyno and the chart looked more like a big v8 than something with only 4 cylinders. Also other factors like using special space shuttle coatings on the exhaust header to ensure the turbo get the ass as hot as possible. Swain tech's white lightning coating is one of the best, Mike used that on his 200SX along with a nickel cadium coating on the outside of the header and after a dyno run we were able to put our hand on the manifold! IIRC swain tech coatings is what NASA uses on various parts of the space shuttle...
This page is getting kinda long so I'll stop here for now
Hope this helps!
