Sensor Questions?

[Edward Hernandez R]

"The airflow into the ports per revolution is almost directly related to the manifold pressure for most engines with a relatively flat volumetric efficiency characteristic."

Most engines do not have a relatively flat volumetric efficiency curve, especially those with tuned induction systems. Virtually all mulitport injected systems utilize tuned induction systems. Only TBI systems, which are essentially fancy carburetors, do not use tuned intakes due to problems with wet flow.

"FWIW, I installed an aftermarket speed-density system on the weekend and was able to tune the efi and distributorless ignition system to a driveable state within two minutes."

Good for you. This is an excellent example of the fact that gasoline engines can run A/F ratio anywhere from 10.5:1 to 15:1(or higher, depending on the combustion chamber) and still be called drivable. That's another way of saying you could get your fueling wrong by about a 30% and the engine will still run. Same goes for spark timing. You can be way off before you would judge a vehicle as not being drivable.
   The point is, you cannot maintain a specific A/F ratio without knowing how much air the engine is consuming or without an accurate, wide range O2 sensor. This is a big point, since the difference between being drivable and passing EPA emissions fuel ecomony standard is enormous for the OEMs. DIYers need not meet these standards.