While replacing my air filter I was looking at the old one and wondering, "I can see this has debris on it, but how much was that affecting airflow to the engine?"
Obviously the more restrictive the air filter, the less air can get to the engine, and hence the less peak horsepower can be produced.
Then I thought, "Isn't a modern fuel-injection engine sort of a large computer for measuring how much air (or oxygen) mass is getting to the cylinders?"
Now I'm wondering:
Is it true in principle that the ECU knows how much air is getting through the filter?
If so, does it log that data anywhere that can be accessed – e.g., are there OBD codes that would provide that, or from which that can be deduced?
If so, can I deduce how clogged my filter is with a single full-throttle run to peak RPMs, and compare the airflow data with those I get doing the same run with a new filter (at the same density altitude)?