Originally Posted by padgett
Exactly. To properly supercharge a gas engine you need to start with something already built like a diesel. The other problem is well, dieseling (or detonation aka pre-ignition). To support max cyl pressures with boost and without detonation you need either 100+ octane (pure ethanol works well) or direct injection and cooling of the charge (intercooling).
All of this is also a factor of bore diameter and speed of flame front propagation. For this a spark located at the center of the chanber helps to avaoid developing a second (or more) combustion point. Lostsa small diameter cyl can support more boost than a few big ones.
You can play a lot but since I prefer street engines to run on 87 PON, the current Pentastar is pretty much at an upper limit and VVT on both intake and exhaust really helps. That some may be a touch over might be a cause of all of the cyl head failures. Will say that on the rare occasions I haul something heavy in hilly terrain on a hot day I plan to fill up with 89 PON.
So if you want to add a supercharger, go ahead. Just be aware that the reason to go to low compression pistons is twofold:
1st: to reduce the compression pressure to avoid detonation (but can control that with the boost)
2nd: to increase the chamber size to increase the mass of the charge you can pack in for a given max BMEP. (where the extra power comes from).
Many miss the second point.
You're over complicating it. Any street enginge does not need all of that. Just a good crank, rods and pistons matched to the proper compression and tune. Most NA engines use cast parts and powdered metal rods. Great for atmospheric pressure, but will fail somewhere over 10lbs. You could probably go to 14 or higher on a turbo and cast crank though. What you are stating really only applies to a high boost, high power build. I have a friend that has over 120,000 on his 4.6 3V mustang with 9.5 lbs. of boost. The SC went on around 15,000 miles.