WARNING!!!!! when using an O2 enrichment system, it is imperative that a protocol is followed prior to attempting to starting the engine. Before attempting to start the engine, make sure the O2 is off and not leaking, redundant valves are a must!!

Prior to attempting to start the engine, evacuate the crank case using CO2 or Argon gas. If the crank case has excessive O2 build up, a back fire can turn the engine into a bomb!! A good PCV system is a must to keep O2 from building up in the crank case during operation.

Next; With the ignition and fuel sources "deactivated" (as in can not possibly function in any way) crank the engine with the throttle (if applicable) wide open for no less than 30 revolutions. This will clear out any excessive O2 that may have built up in the intake and cylinders from leaks or from an engine stall shut down.

Starting an engine with a raw O2 build up can / will result in a very dangerous and memorable time in ones life.

Never add O2 to an engine while attempting to start the engine. Only introduce a controlled amount of O2 after the engine has untainted a stable operating condition.

I worked on a O2 enrichment system on a 2.5L gasoline engine a long time ago. The goal was to increase combustion efficiently and increase mileage at part throttle operation. At less than 50% throttle opening, it actually did not take much O2 to get the PPM ratio to change to a lean and unstable range. The main problem was in getting the O2 evenly mixed in the intake charge, therefore eliminating O2 pockets in the combustion chamber.

At that time, with the funding and resources that were available, the problem of O2 pockets could not be eliminated thought the entire operating range. The pockets caused an un-uniform flame front, detonation, preignition, uneven thermal distribution (hot spots), and erratic speed control.

IMO, Nitrous is a better choice for an additional oxidizer.