My turbocharger candidate list is still open while I try and find an upgrade that fits what I am looking for. A potential contender is a revised FrankenTurbo F21 that Frankenturbo released some early prototype photos of.
A revised, billet, compressor wheel:
FrankenTurbo F21 Billet Compressor
and even more interesting, a mixed flow turbine:
FrankenTurbo F21 Mixed Flow Turbine
This looks to be an excellent combination for trying to maximize power on a stock motor while retaining good spool up characteristics.
Time will tell if the prototype lives up to the design goals.
One of the areas of performance I was especially interested in evaluating was the boost level that the F4H-BT could sustain. To this end EPL provided a high boost tune that started in the 27 psi range and then tapered down to 25 psi around redline.
After establishing what the turbocharger was capable of in terms of boost level I asked EPL to back off the boost some to a level I felt more comfortable operating at for an extended period. The result was a boost level around 23 psi.
The end result, performance on the road with the different boost profiles, was closer than I would have anticipated. While the 27 psi profile did produce a noticeable increase in performance early in the rpm range, and FATS time was about a tenth of a second quicker, 3.2 sec. versus 3.3 sec. on average, the higher boost profile did not exhibit greater performance with increasing rpm.
