I know I know, I had told myself that I was NOT going to boost my 6... buuuuuut now I'm scheming 
Eventually I plan to get an NC2 Miata and make a boosted track monster with 15psi+, and I know the 6 will never be THAT, but after reading about the Kraftwerks complete supercharger kit for that car started to inspire me to do that to the 6. Instead of gaining +140hp, with this motor I think we're looking at only gaining +50hp
GOALS/POWER:
A reasonable level of boost, figure at least +50hp, while maintaining longevity/daily-driver ability.
*UPDATE -
DRTuned will support tuning for forced induction for $999, possibly OVTune as well but no response yet.
VT-Racing - Anrot Industries
A new Chinese manufacturer (bunch of products released in june 2019) of twin/screw superchargers for dozens of models of car, most don't apply to American markets, but includes a kit for 2.0L and 2.5L Skyactiv motors.
BUT no pre-established path for sale in the US... working on it.
Kit is quoted at $4-5k + $1k for tune - so $5-6k total, for close to 300hp-crank...
COST: $4,200-$8,000 $2,400 Supercharger - Rotrex C30
Rotrex Superchargers build their boost gradually as RPMs rise, so it's very gentle stresses on the engine/trans/drive shafts.
Plan to lower the redline to aid longevity (at least down to 6000rpm, likely even lower on my buddy's cx5 with different pulley size to give more boost at lower rpms)
Reference: 16psi doubles air volume, so every 1psi is 6.25% more air volume.
Example range of boost/rpm that I think would be very safe.
@3000rpm 2psi +12% air volume , ~7% real HP gain
@6000rpm 8psi +48% air volume (Redline, peak possible boost), ~29% real HP gain
estimation that 70% of are volume increase converts to power gain, so in above example that's a peak of 29% power gain
Systems Considerations/Thoughts
Eventually I plan to get an NC2 Miata and make a boosted track monster with 15psi+, and I know the 6 will never be THAT, but after reading about the Kraftwerks complete supercharger kit for that car started to inspire me to do that to the 6. Instead of gaining +140hp, with this motor I think we're looking at only gaining +50hp
GOALS/POWER:
A reasonable level of boost, figure at least +50hp, while maintaining longevity/daily-driver ability.
*UPDATE -
DRTuned will support tuning for forced induction for $999, possibly OVTune as well but no response yet.
VT-Racing - Anrot Industries
A new Chinese manufacturer (bunch of products released in june 2019) of twin/screw superchargers for dozens of models of car, most don't apply to American markets, but includes a kit for 2.0L and 2.5L Skyactiv motors.
BUT no pre-established path for sale in the US... working on it.
Kit is quoted at $4-5k + $1k for tune - so $5-6k total, for close to 300hp-crank...
Rotrex Superchargers build their boost gradually as RPMs rise, so it's very gentle stresses on the engine/trans/drive shafts.
Plan to lower the redline to aid longevity (at least down to 6000rpm, likely even lower on my buddy's cx5 with different pulley size to give more boost at lower rpms)
Reference: 16psi doubles air volume, so every 1psi is 6.25% more air volume.
Example range of boost/rpm that I think would be very safe.
@3000rpm 2psi +12% air volume , ~7% real HP gain
@6000rpm 8psi +48% air volume (Redline, peak possible boost), ~29% real HP gain
estimation that 70% of are volume increase converts to power gain, so in above example that's a peak of 29% power gain
Systems Considerations/Thoughts
- AIR - Intake/Throttle body/MAF: Stays same - the 2.5L already uses the same one as the 2.5T, so I think that'll work.
- FUEL - Injectors/Pump: Stays same - I'm assuming the existing injectors could handle +25% duty cycle. If needed may try to use injectors from the 2.5T version.
- Water/Meth Injection - Will consider adding as this can dramatically boost effective octane, helping to offset effects of the increased boost pressure. Main motivator to potentially go this way is to increase safety/protection from detonation, but could also get more power.
- TUNING - DRTuned will support forced induction tuning for $999, he said to expect over a dozen revisions as we safely extract more power
- TRANSMISSION - should be ok, but going to change fluid more regularly to be cautious. AFAIK the same transmission is used in the 2.5T, all indications are that it can handle this just fine, again centrifugal supercharger characteristics make it super gentle on transmissions as it builds power gradually.
- ENGINE - It's hard to know how much the internals of an engine can take, how over-engineered are the pistons/rods/connectors/etc. That's why I have lower power targets, given the already high compression nature of this engine it is not practical to expect to safely push more than 8psi.
- Theoretically you could do a partial engine rebuild with pistons/parts from 2.5T to reduce mechanical compression ratio down to 10:1, allowing you to push 14psi, BUT at that point you'll need to upgrade to a different scale, so that is not in scope for this build.