One thing I noticed in this video, and that was the discussion around the air injection tubes at the exhaust manifold. I would like to take this time to help clarify how they work.
By trade, I am an automotive engineer, and like to use my 1970s vintage car for ‘show and tell’ at the local car shows. I keep mine fully emissions equipped, just as it left the factory, in an octopuses mess of vacuum hoses and feedback systems. I like it this way, because of how I can teach even lay-people (even kids!) at shows how simple it actually can be, and can even with proper direction, goad them into ‘designing’ the same type of system on their own, which really surprises them when they realize the mystery is not so mysterious afterall. That is why I sometimes feel a little like a ‘troll’ regarding what could be taken away as misinformation about some of the systems.
The air injection system (called “Secondary Air Injection”), was not just a ‘dilution’ device, meant to ‘water down’ the excess pollutants in the tail-pipe outlet. The secondary air injection system solved a crucial issue of ground level smog. How? As an engine burns its fuel charge, there are inefficiencies of combustion inherent to the design. Combustion chamber geometry, quench zones, poor spark propagation, you name it. Unfortunately, this means that not all gasoline (in this engine’s case) is fully burned. You can smell this at any car show when a car drive’s on by. That classic ‘overly rich’ exhaust smell that you don’t notice with today’s cars. That unburned gasoline? Those are called ‘hydrocarbon’ emissions, or just ‘HCs’ in shorthand lingo. Get those up into the atmosphere, and through the wonders of chemistry, they transform into ground level ozone after being catalyzed by high humidity and elevated temperatures (think ‘ozone action day’). California felt they had enough smog already, so they requested a fix to the tail-pipe-out HCs (a stance later taken up by the EPA-at-large in following emissions years). So, how do you get rid of unburned gasoline vapors in the exhaust? Maybe try to burn it in the exhaust pipe? The auto industry thought it was worth a shot. The fancy term for ‘burning’ fuel is ‘oxidize.’ One problem, there was no longer enough ‘oxygen’ to ‘oxidize’ the HCs in the exhaust. So, the path they chose was secondary air injection (“Thermactors,” “Smog Pumps,” insert hot-rod lingo here). Exhaust is generally already hot when it leaves the cylinder. Hot enough to burn away HCs. By adding a fresh air charge into the exhaust, there is now some oxygen to oxidize, or burn away, the excess HCs. With the unburned tailpipe-out HCs mitigated (it was not 100% efficient, but still felt to be worthwhile), the car could now make California happy[-er]!
As for the power loss? Well, I can’t argue against that. Every accessory or bearing surface contributes a parasitic load. And while I have never seen a dyno result (especially one that I would consider reliable) to clearly indicate the amount of parasitic losses an air pump contributes, I would hazard a guess the air pump is far less than most people think. Probably less than 5 hp, but admit I’m guessing here (based off of heavy duty diesel air compressors running at 90 psi, much higher than a secondary air injection system).
Thank you for reading!