O2 "injection" at altitude to get power back?

I have a friend that did Oxygen injection with a V8 Vega years ago. He did it to be different and he had a lot of the parts laying around already. But basically it's much safer to accomplish the same thing using NOS. The reason the NOS gives you HP is the oxygen content is higher than the air we breath. With straight O2 things could go wrong real fast!

 

You don't have to get that sophisticated...

What limits the available O2 for combustion at altitude is not the lack of it --- up to about 18,000 feet, the relative concentration of O2 in the air is not much reduced from what it is at sea level. However, the partial pressure of the O2 (and the total pressure of the air mixture) is greatly reduced as altitude increases. Therefore, not as much air (and O2) will flow into the cylinders --- lower flow rate resulting from smaller pressure differential plus lower total, specific filled volume (in other words, the air isn't pushed as hard into the cylinder and the cylinder will contain a lesser amount of air molecules when filled).

The simple solution to this is Turbo / Super charging which forces more air into the cylinder than the natural flow at altitude will allow. Properly (good ECU maps) turbo-charged engines will compensate very well and run nearly as well at altitude as they can at sea level.

For a normally aspirated engine, rather than introducing additional compressed O2, you really only need to introduce compressed air (much safer and cheaper than O2). Also, you can't simply "inject" it --- you need to deliver it in a manner which allows it to be metered by the intake / pre-combustion sensors (MAP, etc.). Furthermore, just pumping O2 (or standard air mixture) directly into the cylinders would really screw with the ECU, as the post-combustion sensors would be telling it one thing (O2 content is adequate), but the intake sensors would be telling it something else (pressure can't match O2 level). In that case, the ECU would probably struggle to set ignition and fuel delivery points to values that would be balanced and able to safely compensate.