The 2650 cannot run on 6s safely because it will have an unloaded RPM of over 60,000. 4s for the 2650. Let me point this out, we're trying to figure out if a Chevy Cobalt would be better with a V12 or V10..................its darn near overkill either way, and way more than enough power with the 2650 or the 2200, trust me. BTW the 2650 is actually more "manageable" on 4s than the 2200 on 6s anyways.