We have to remember that normally aspirated (NA) engines tend to have a few challengers, or limitations, under boost. I'm not saying that you can't make some nice power with a bolt-on blower, but you just won't see HUGE power until you make some physical changes to the motor.
1.
High compression. NA motors tend to have higher compression, compared to what you would pick for big boost. Detonation is one of the biggest enemies of the internal combustion engine, and high static compression plus the added heat of boost tends to REALLY increase combustion chamber temps, leading to dangerous detonation. Now, this can be partially helped by smart intercooling (to lower temp), plus i suspect that the wonderful shape & efficiency of our beloved hemi motors may tend to avoid "hot spots" that plague other head designs. But the simple fact is that the 10.3 (?) static compression ratio of the 6.1 Liter Hemi is not really blower-friendly.
2.
Strength. NA motors with cast rods & pistons have a strength limit, and it takes strength to make power. Our 6.1 Hemis have forged crankshafts
but cast pistons & rods
3.
Camshaft overlap. Overlap helps scavenge the cylinders in NA motors, but is not required in blown motors ... where the intake charge is pressurized to "explode" into the cylinders. So cams with moderate-to-large overlap, which may be friendly for NA motors, is not the best choice for boost applications.
4.
Tuned, or restrictive, exhaust. Tuning the exhaust system can also help scavenge NA motors, but boosted applications tend to favor the biggest, most open exhaust system possible.
These are just a few reasons off the top of my head why simply bolting a blower onto a motor designed for NA use ... even with good injector & timing tuning ... has to be done cautiously, and will have real limits on how much power you can make.
Having said all that, the sight, sound & power of blown Hemi under the hood of a new Challenger makes me all gushy inside
)
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