So, an advanced builder.....Normally aspirated rotaries play nice. They produce enough power for most applications. They are tolerant of abuse at the hands of the "Unwashed". They run on when massively

overheated, when ignitions are far over advanced, in the presence of "Marvel Mystery Oil" and similar home brew concoctions. For an amazing distance with no oil pressure at all, and so-on.

 

Turbo charged and supercharged rotaries do not play nice. They require special care to avoid a long list of seemingly innocuous data points. Because: Where the rotary's huge expanse of cold combustion chamber and sluggish burn rate favors low octane fast flame front fuel, this is not enough help for the pressurized induction system. Where effective compression ratio may be doubled. (Twice the fuel and air in the same space) So, ignition advance may start off with very low numbers and retreat rather than advance as RPM (And boost pressure) goes up. Because the fuel droplets are now closer together and burn more quickly than in the unboosted version. The heat load on the cooling system goes way up as well. Burn twice the fuel,

remove twice the waste heat. Remember the engine is only 28% effective so about 70% of the fuel is just a roaring fire under the hood that must be piped overboard as waste heat.

 

While it is difficult to detonate an NA rotary, (although my driver figured out a way) it is not at all difficult to detonate a turbo rotary. Detonation is charge temperature dependant. See "Why intercoolers".

 

Detonation is an ignition event starting AFTER the planned ignition event at the plug away from the plug area (usually) . So the fuel mixture was too lean (we fuel cool at high power settings)  Coolant temps got too high.

Boost got too high. Carbon deposits on the rotor, octane rating too low, and so-on. Anything that adds to charge temperature.

 

Anything that starts an ignition event BEFORE the planned ignition event has started PRE ignition. This problem is also very harmful as it raises engine temps and leads quickly to Detonation. You can have one or the other or both at once. (Very bad). Pre ignition is not charge temperature dependant but as you can imagine that could add to the problem. Faulty ignition system. Cross talk in primary wires. Induced voltage in secondary wires. Plug heat range too high. Plug tip shape wrong. Injector skipping or plugged. Carbon buildup on the rotor.

 

Look for cracks around the plug holes in the rotor housings. Look for rounded electrodes on the plugs.

Look for the mating surfaces of the rotor housings to be blackened from scrubbing on the irons around the plugs. Very high output rotaries use the dowels in every bolt position to prevent the (rubber like) rotor housings from changing shape with each power stroke. Measure the width of each rotor housing between the plug holes to see if the housing has shrunk in that area (Been over heated) 

 

Use NGK R-6725-115 plugs.This is a retracted gap fine wire electrode. The 115 is actually the heat range (11.5). I gap mine at .010" (ten thousandths). And use an MSD 6AL CD ignition box on leading and trailing. Both leading and trailing fire together (Less complexity)  at between 24 to 27 degrees of advance. However we are doing all of our work above 7,800 RPM. So, less advance is needed for 6,000 RPM normally aspirated and nearly none for turbocharged at 6,000 RPM.,   Take a deep breath. Those plugs are about $27.00 each.

 

I think a change has occurred in your program that is just not obvious. Perhaps a bit of pump impeller is eroded away. A bit of coolant hose is sagging or crimping in exactly the wrong place. The timing marks were off a bit all this time and advance was a bit more than was thought. Use the starter ring gear teeth for timing marks. Much bigger circle. Easy to see. It sounds like overheating, maybe in just one location rather than a catastrophic failure that would leave clues behind.  Copying mapping from a street racer can be misleading because he is using his engine for a few seconds at a time. Our duty cycle is close to 100% Stand on it and steer for hours. So a piece of ducting changing shape can do this. A dirty cooler. A trim change. Map richer for wide open throttle. Cool with fuel. (Lower charge temperature). WWII planes had water and alcohol injection at full throttle, to lower charge temperature and raise octane rating.  You will find it. Fear not.

 

Lynn E. Hanover