[quote]ORIGINAL: PAINLESS

. Higher nitro content in the fuel will also generate more heat and can just make pre-ignition worse. If your running 30% try 25%, that will help too.
quote mgtman
you are right but its comon logic to richen up when using higher nitro
Higher nitro content Rich
Lower nitro content Lean
Higher oil content Lean
Lower oil content Rich

Changing to a higher percentage of nitro fuel sounds like an easy method of developing more horsepower, but it isn’t always that simple. Without getting into all the particulars of nitro fuel, I’ll just say that there is a point where you can have too much nitro. Adding up to 10 percent more nitro than is typical produces more power, but you have to know how to adjust your engine to accommodate the extra nitro. Fuel-mixture settings need to be slightly richer when nitro content is increased. Also, you may have to increase head clearance by adding an extra head shim. The extra fuel introduced into the combustion chamber increases compression by adding non-compressible matter; this also increases cylinder pressure during the combustion process, which may cause detonation. Detonation occurs when the fuel explodes instead of burning, and that can cause internal engine damage. The extra head shim will likely prevent detonation when fuel with higher nitro content is used.

A final note about fuel: fuel with a lower oil content (for manufacturers that actually disclose the amount of oil in their fuels) should be run with a richer mixture setting. This doesn’t so much relate to performance as it does to the benefit of the engine. Conversely, fuels with higher oil content have the extra lubrication that allows a leaner mixture setting with less risk of engine damage. Fuels with a lower concentration of lubricant are intended for competition use by experienced engine tuners. These fuels will make marginally more power because the lubricant that’s removed is replaced with power-producing nitro and methanol. Evaluate your tuning ability honestly before you run out to buy fuel with a lower oil content.
http://www.*********.org/understanding_fuel.htm