Retarded* timing Advanced timing + turbo = boom. Increased charge density from >atmospheric pressure causes faster flame propigation and pushes the fuel close

Retarded* timing Advanced timing + turbo = boom. Increased charge density from >atmospheric pressure causes faster flame propigation and pushes the fuel closer to its knock point when compressed. Turbos also run a richer mixture under load to cool the intake charge. Richer mixture and a comparitively later burning and therefore hotter exaust stream increase exhaust temperature (along with the ability to produce more power aka burn more fuel)