First off, I am no expert on turbochargers; I just gained some understanding and appreciation for the basics.
One of the BEST guys when it comes to turbochargers is Patrick, the mod of the turbo section.
I started this turbo study journey, because
no one (vendors) wanted to talk to me about “Hot Air Turbo’s” other than the TA33.
Too small of a market, too big of a headache.
So I had to read, study, etc to make informed decisions instead of throwing $$$ at it.
Anyway …………
Well, it appears that that wheel is “out of breath” around 23 PSI for the 60lb/min flow mark based on the compressor map.
You will also notice that that the wheel rpm is very close to it’s max of 120,000 RPM.
Did some additional in-depth sampling analysis based on the question.
For the 60-1 Trim wheel;
Calculated compensated flow requirement is 796 ACFM at 58.8 lbs/min @ 23 PSI boost, based on 6000 RPM, 200F intake temp constant, 70% wheel efficiency, 231CI motor
It appears that this set-up will run to the right of the map, but, the map should only be used as a guideline in the selection process as there are too many variables that affect the map.
When I ran the numbers, it appears that this set-up should produce close to a calculated 11.98@113 in a 3500lb car.
The TA49 has been rated at BOTH 545 (Precision) and 475 (Limit) ..... I have some ideas “why” (In my head)
Looking at it more closely; TA49 uses the same wheel as the TA33, a 60 trim
If you look at the posted map, is appears that this wheel is out of breath around the 19PSI, but, real life test data indicates the sweet spot to be 23 PSI or 2.65 PR
Sure, you can run this turbo to 23 PSI, but, it puts the requirements placed on the wheel/turbo "off the map" but the TA49 has gone faster than anyone imagined it ever could at much higher boost pressures! I doubt it is an "off the shelf TA49" ....... There has got to be HP secrets there, and no doubt an AWESOME tune!
Over the years, it has often been stated that the “rule of thumb” is 1lbs/min=10 hp.
You can see this is why the TA54 is rated around the 610 HP mark.
But there is more to that. Charge temperature for this application will affect lb/min, so on a HA you need a BIG turbo since hot air takes up more volume.
This is why many many moons ago Lee Thompson stated;
“A turbo is big enough when you can’t close the hood”
Clear as mud right??? :wink: