We found some interesting things on our turbo SB2.2 engine that was having detonation problems at high boost [36 lbs]. first eliminated the electric water pump and installed a Stewart stage three pump,made up pulleys to run the pump 10% faster than crank speed. installed -12 lines from pump to bottom center of the block with a restrictor behind the pump with a 7/16 hole,forcing most of the water to the bottom center of the block.installed restrictors at the 4 outlets of the cyl heads where water enters the manifold.
All of this increased the pressure and scrubbing action behind the combustion chamber walls and prevented the water from flashing to steam.we also installed a Schraeder valve in the radiator and using a 28 lb radiator cap pump the radiator up with air until you hit the 28 lbs. this raises the boiling point of the water way up. the combination of all this cured the problems completely and the same modifications would probably help you N20 guys as well.Bill
Hendrens Racing Engines
1310 U.S.Hwy 221 North
Rutherfordton North Carolina 28139