When the SCCA forced us rotary people to use racing gas Darryl Drummond Dynoed one engine with both fuels Street high test 97 Octane and VP 110 Octane racing. The racing fuel cost 4 HP over the street gas. The SCCA relented and we got to use street gas again.

You get the power back from racing gas by running 14:1 compression ratios.

 

I use 87 Octane for racing. No alcohol of course.

 

Alcohol =                    80,000 BTUs.

 

Typical street motor fuel

regular no alcohol = 119,000 BTUs.

 

Low sulphur #2 diesel= 130,000 BTUs.

 

Bunker C

(Used on old ships) = 145,000 BTUs  

 

The turbo charged rotary should be thought of as a different engine. Only similar to a rotary.

The boost allows for over filling the chamber with mixture so that the engine is (in effect) larger in displacement. This increased volume of mixture is compressed into the same head space as the NA engine, so the effective compression ratio goes up. Maybe way up dependent on boost pressure.  So the compression ratio becomes variable as the RPM go up and down. More boost means higher heat of compression, so if more than a few pounds are used, an intercooler is used to reduce the intake air temperature.

 

Remember that detonation is charge temperature dependent.

 

The turbo engine is typically more efficient than the NA engine due to the higher effective  compression ratio. The cold combustion chamber helps in the turbo so higher boost can be used without detonation problems. Less unburned fuel is left behind, and what is keeps energy to the turbo high. Energy removed from the exhaust to spin the turbo reduces muffling problems. For high boost engines the ignition map is nearly backwards. At high boost the timing comes back towards zero advance, as flame speeds in the high pressure chamber go way up. The ignition system must be programmable.

 

Lynn E. Hanover