Interesting findings in the MHI TD04 Family . Long post alert .

[discopotato03]

Hi all , after hours spent chasing facts and figures on IHI turbos (early and late) , and MHI's TD04 family I now have to agree that there are a few good things from later generations .

I first went looking at ball bearing IHI turbos aimed at Impreza's and Legacy's but the problem is that many of them are just a bit too big for what I'm aiming at power wise . There are all sorts of detail changes to the more performance oriented EJ20/25 turbo engines and these larger turbos can be ok if you have that level of engine technology . Some examples of engine enhancements are larger ports and valves , individual throttle per cylinder , variable cam timing , twin scroll headers and turbine housings etc etc .
Without spending squillions an EA82 can only dream about these things .

So armed with the approximate turbine and compressor dimensions inc blade count I searched through the later IHI turbos and the only one that I thought came close was the VF40 from 2005 odd Legacy Turbo .
I also searched around for details of MHI's TD04 family and there is a lot more available in them than just the WRX's TD04L-13T-6 .

I'll go through the dimensions of the more common TD04 turbines and throw in the TF035 ones for laughs .

TF035/TD04 Turbine Wheel dimensions .

................ Inducer/Exducer/Tip height/Trim .
TF035HM ... 42.5 ... 35.0 .... 6.5 ..... 68T
TD04L ....... 46.8 ... 41.2 .... 7.7 ..... 77T
TD04 std ... 47.2 ... 40.0 .... 6.8 ..... 72T
TD04H ...... 52.0 ... 44.0 .... 7.7 ..... 72T
TD04HL ..... 52.0 ... 45.6 .... 8.9 ..... 80T

TF035/Some TD04 Compressor Wheel dimensions .

............... Inducer/Exducer/Tip height/Trim .

TF035-12T .... 37.8 ... 49.0 .... 5.0 ...... 60T
TF053-13T-4 . 38.3 ... 51.0 .... 5.0 ...... 56T
TD04-13T-6 .. 40.64 .. 56.0 .... 5.0 ...... 53T
TD04-15T ..... 42.0 ... 56.0 .... 5.4 ...... 56T
TD04-15G ..... 43.37 .. 56.0 .... 5.4 ...... 60T
TD04-16T ..... 43.40 .. 56.0 .... 5.7 ...... 60T

So as you can see there is a bit of variation in what is said to be suitable for Subaru 2000cc 4 cylinders . The TF035 compressor dimensions are quite small and fit roughly in the small end of the TD04 compressor family .
The TF035 Turbine is smaller than the smallest TD04 one and this is why TF035's are really a separate turbo family . Turbo families are usually based on their turbine family .

I found some interesting threads in NASIOC and one particularly where a feller was porting turbine housings and came across a JDM TD04HL amongst a group of USDM TD04L's . He tried in on his own car (Rex) and found not surprisingly a significant difference in performance .
I take the time out to listen to GC8's round the place and the later TD04L equipt ones sound like they spool up reasonably early . Most Impreza people say that these turbos support an easy 200+ ponies so the compressor side sounds about what I need .
From looking at TD04 turbine specs and applying a bit of previous Garrett experience I reckon a hybrid of a std Impresa TD04L-13T-6 with the next up incremental sized turbine (TD04H) would make the thing breath a little better on the hot side . It's trim size at 72 is better than the TD04L's 77 IMO and would help make the thing responsive without being restrictive .
I'll have to talk to my turbo people to see if a "TD04H-13T-6" is available new or what the cost of an Impreza turbo rebuilt with the "H" turbine would cost .

Enough for now , cheers A .

[El_Freddo]

Good write up Adrian. Loved the warning in the title.

Keep up the good work

Cheers

Bennie

[discopotato03]

I also need to ask around about those Impreza TD04L 13T-6's because I think there was a minor turbine housing change in the post MY00 cars .

Cheers A .