your math is a little off... its actually more like a 60 trim. the equasion is (inducer/exducer)^2x100

therefore, it takes it from a 50 trim to a 60 trim

you forgot to square it

and for everyone else out there, no, it is NOT the same as a "50 trim" as it it commonly referred to

 

Cheers. Forgot it was area ratio, rather than radius ratio.

The only Garrett wheels I see with 60 trim are the Disco Potato, and some of the really little Garrett turbos. Most of the middle-sized turbos are 48 or 52 trim, like the 71mm wheel, but it depends on the housing. Largest big turbo Garrett trim is like 56.

 

when you consider what's going on, then area makes sense....

as for the garrett sizes, the turbo that is commonly referred to as a "50 trim" is actually a "51.6 trim"


the trim really has nothing to do with the turbo size... jsut some turbos have been nicknamed by their "trim" which has little to do with how much power it can make

 

I'm dredging this thread up because there may be a few points unknown to some .

I was reading a while back where Dave B mentioned that testing either the WR or the Evo Green turbo that the 5/10 bladed compressor worked better than the 6/12 bladed one .

From what I've seen there are a fair few high flowed turbos getting around for various production engines and they mostly reuse the std OEM or similar turbine housing , it makes sense because it bolts back in between the std manifold and dump pipe (O2 pipe) . Generally its not too difficult to fit a larger capacity turbine and compressor/comp housing but the standardish turbine housing remains .

It now gets interesting because the compressor and turbine need to match each other speed and capacity wise and ways need to be found to get more exhaust gas through that limited sized turbine housing . So you go ahead and fit a larger similar family turbine and compressor and find the turbine inlet pressure (backpressure) is a bit high and starts to strangle the engine . You could try a few various things to to fix this but if you can use a compressor with less blades (meaning more revs to pump the same volume of air as the 6/12 blade one) Then obviously the turbine speed has risen for the same compressor output .

I see two worthwhile advantages in doing it this way .

Firstly at the spool up phase the compressor has less load on it because the mass of the air that its churning is less . So with less work to do the turbine is going to want to spin up more easily given the same exhaust gas velocity energy .

Secondly a turbine spinning faster poses less of an exhaust gas restriction than one turning slower so I'd say in the Green turbos instance they've got a higher flow rate through the 9's 10.5cm housing but allowing the rotating assembly to spin faster than it could loaded down with the pumping loads of the 6/12 bladed compressor wheels .


Now someone mentioned the HTA35R and Garretts GT4088R in relation to their compressors blade numbers - both 7/14 I think .
Now where I see the GT4088R being different is that the wheel trims are smaller than many GT BB turbos at 78 and 52 for its turbine and compressor . If any of you followed the development of the original BB GT40 turbo you'd remember the trims were more like 84 on the turbine and possibly 56 on the compressor . A few escaped captivity at the testing stage and the results were said to be pretty **** poor . I would put that down to the turbine trim being too big (like 30R's and 35R's) and the compressor being out of step with the turbine speed and pumping capacity wise .
Now I don't know if the GT4088R's C117 7/14 bladed compressor is a completly new development or if its just the same as a 6/12 bladed GT40 compressor with another pair of blades - and in the smaller 52 trim . Whatever they did its turned out to be a great match and a real good thing in its size range .

The HTA35R (speculating here) is probably along the same lines as above only FP obviously didn't have the luxury of being able to alter the turbines trim size . My guess is that Robert (or whom ever) experimented with a slightly smaller diametre compressor in possibly a smaller trim but with extra blades to move a similar volume of air as the 6/12 bladed 56T 82mm GT40 compressor . The one chosen looks to have been a slightly better match than Garretts original and its showing up as earlier spool and probably better transients .

If I was developing what some call the GT37R (I prefer T04Z) I'd say its going to be easy to lose that T04R compressor they have standard . Its a bit of a strange beast because of its large trim size (63T) and being a T series wheel probably wouldn't have some of the smarts in true GT (Garrett technology) series wheels .
The T04Z's nearest cousin in the ball bearing P/60-1 turbo and its virtually identical except for its 60-1 compressor . If a more modern wheel can be found maybe slightly bigger than the 60-1's ~ 76mm but in a smaller trim than 60 then good gains could be had .
The thing thats always going to be a bit painful is that P trim turbine with its heavy mass and T series technology . I think is main advantages are its wide tips and the 76 trim size .
In a perfect world Garret could give us their GT37 turbine in a smaller trim size and Ultra High Pressure ratio (UHP) material/design . With an appropriately sized C117 compressor and a high temp twin scroll turbine housing it could be a real beast .
Could do the same with the 35R as well , they may not need to do it with the 30R series because they already have the 60mm NS111 turbine from their TR30R competition turbo and that could do things the GT30UHP turbine never will IMO .

Anyway , food for thought , cheers A .