The Chieftain engine (Lyc. TIO-540J2B or J2BD ) ALREADY HAS A VERY LOW COMPRESSION RATIO! ~ 7.3:1.
You cannot lower the CR any further - - nor can you retard the 20 dBTDC timing any further and then still be able to operate the engine at normal power settings. (With or without “smart” EIS and/or with intercoolers.)
Why not ?
See if you or others can identify the specific operational reason why that cannot (does not) work ?