Wish I'd had a dyno for some
better data. The B&M book charts for this engine with my mods showed
(estimated) about 380 HP, up from unblown about 270. Any other comments on
engine HP needed to drive a centrifugal supercharger?
T
"Terrence, I do not have any 1st hand
data...I sent out a feeler to an old General Motors engineering buddy...I'll let
you know if I get any real data. Craig Berland"
Well it wasn't fast, but here is some general info. First, if
you are running high pressure ratios with a roots type supercharger, then the
parasitic losses get very high. With that said, GM is introducing a "roots type"
supercharged V8 with peak HP occurring at 5400 RPM. The parasitic loss for that
engine with a pressure ratio of less than 2 to 1 is 60 to 85 hp depending on the
inlet air temperature. For higher pressure ratios they would go with a
screw type supercharger due to the increasing parasitic losses. The
problem with a screw type in autos is the losses during part throttle
operation. This requires a clutch to overcome. The benefits for a
supercharger over a turbo are response, packaging and emission
converter light off. Packaging could be of interest to us, the others are not.
Another tidbit....if you disconnect the supercharger belt at 65 mph, the fuel
economy goes up 6 mpg. This vehicle is a 4.5 second 0-60 car. To put parasitic
losses, blower size and pressure ratio in perspective...I was told by the
engineer who designed and built the screw type superchargers for top fuel
cars that 20 years ago it took over 500 hp to spin the roots type blower in
a top fuel car. Not exactly new data but still relevant.
Craig Berland