Lots of questions about amount of boost. This is where it gets interesting! Our dyno is very close to sea level, those at higher elevations will see lower boost than we get here. Our RF did as much as 13 PSI with totally stock exhaust system, 12psi with our standard length RoadsterSport header and smallish stock midpipe. Our Race ND in this thread with same pulley only does 8 Psi... yet even 'untuned' the first power pull numbers for this car were HIGHER than our RF. So, that's 8psi makes more power than 12 psi! Does that bend your brain? How is that possible?
The 2.5 bar Bosche sensor is in the manifold for the blower. Thus, our sensor position is really measuring back pressure...not telling us cylinder pressure. Skyactiv head is extremely tight, all the air is pushed through two very small holes per cylinder (one larger and one smaller port but both small compared to MZR motors). We normally think of more PSI to make more power, and that is true if 'all other things are equal' but once we open flow through the head and out the exhaust we massively reduce back pressure in the supercharger manifold and the sensor there shows lower pressure because the air the supercharger is trying to push into the cylinders and into the exhaust is getting there with much less resistance. This car has a ported and polished head that flows as much as 40% better. Thus, in this case, lower PSI does NOT equate to less power, there are actually more air molecules getting into the cylinder and making more power despite the lower PSI in the manifold. It does mean lots of custom tune work to get the tune right, more logging work later today, hope to get back to dyno for numbers late next week.