Superchargers have literally 1000% more limitations than turbo.
NOT from me. From this forum > 14 years ago.
EATON M90 vs 1FZFE ENGINE
Ok boys and gals:
To really put the turbo vs sc debate to numbers, let's take a gander at what TRD did on the M90 kit. Using a 3.2" pulley, the SC drive ratio is 2.40625. That puts max SC speed of 12,031rpm at 5000 engine rpm. For engine cfm flow I used a typical roller coaster type ramp on the spreadsheet with 100% Volumetric efficiency at peak torque, and 85% VE at peak HP, with 80% min.
The results indicate that this M90 is matched almost exactly with the engine demands at 7psi (1.5Pressure Ratio). Picking a couple of points, here's what I get.
1000 eng rpm = 2406 SC rpm = 096cfm engine demand = 100cfm SC
2500 eng rpm = 6016 SC rpm = 230cfm engine demand = 230cfm SC
4000 eng rpm = 9625 SC rpm = 408cfm engine demand = 430cfm SC
5000 eng rpm = 12031 SC rpm = 480cfm engine demand = 530cfm SC
The maximum HP draw at 1.5PR BTW is 7hp at 1000 eng rpm, and 33hp at 5000 eng rpm. Volumetric efficiency offsets that in a big way, the starts at 70% at 1700rpm engine speed and increases to 90% at 5000rpm engine speed.
What do I make of all this? The M90 in stock trim is about as well matched to a compressor in terms of demand and efficiency as one could find. Put another way, you could spend several fortunes on turbos and never get close to this kind of match, btdt. Change the target boost however, the turbo starts to gain back a deficit.
That reaffirms my conclusion that the SC isn't the problem on the dyno, it's a IC/fuel/timing/exhaust (read: ancillary) problem.
HTH
Scott Justusson
QSHIPQ Performance Tuning
Chicago IL
94 FZJ80 Supercharged