With the passage of a few months a new candidate has entered the scene. I noticed that Silly Rabbit Motorsports has introduced a K04 hybrid variant to provide another option for me.
These SRM turbo’s bring a new twist to the candidate pool because they are similar in size to the FrankenTurbo F21 and ProjectB5 RS4-X on the compressor side, though the SRM uses a billet compressor wheel, but on the turbine side it is using a clipped wheel.
This is a very interesting development since I have theorized that one of the reasons my experience with the FrankenTurbo F4H-BT did not show much gain in the upper rpm’s, despite pushing 25psi out to redline, was that the airflow through the turbine side began to back up lowering the engines VE. Perhaps a clipped turbine wheel would allow this size turbocharger to hold that 25+ psi and flow better, netting greater top end horsepower results.
Since the product is a recent introduction it remains to be see how they perform, but for now they will stay on the candidate list:
- BorgWarner K04
- FrankenTurbo F21
- ProjectB5 RS6-X
- SRM Billet K04
Note: As of July 2015 I have yet to see any results of how the SRM billet K04 turbocharger performs.