Originally Posted by cdelong

higher nitro raises engine temps unless you take action on tuning the engine. to compensate for this you need to richen the needles. if you leave the needles alone and go from 20% to 30% let me know how long before your engines performance degrades. If you're already on the edge with 20%, you'll detonate the engine for sure going to 30% without richening the engine.

Nitromethane provides more oxygen to the engine as it atomizes and the more oxygen you give going from 20% to 30%, the leaner (hotter) your engine will run unless you richen the needle. Higher nitro fuels also have a narrower tuning range. With 20% you may be good within 1/4 turn on the top end needle.... 30% you will need to be within 1/8 turn or less (numbers just for example- not exact).