Engine computers—what are they thinking?
Illogical acts by a logic device.Click thumbnail to view full-size
Been there, done that
I've been in the auto repair business for an eternity, when I started the closest thing to a computer in cars was the 8-track tape player. I have witnessed the birth, growth and complete domination of electronic logic devices on nearly every system of the modern vehicle.
Understanding the desires of your engine computer is a fun way to, oh wait! This is not about fun it's about reality. Your engine management system has a secret agenda that might surprise you.
Surprise! Running & driving is not the primary concern.
It might come as no shock to a some auto mechanics but for most people the secret desires of your engine computer (also called PCM [powertrain control module], ECU [electronic control unit], and some other colorful euphemisms) are stunning.
If you guessed by this time that I'm talking about emissions then you are right. The priorities of the logic in your ECU are with a few variations:
- closed loop fuel control
- heat up the catalytic converter(s)
- purge the canister
- maintain optimal fuel ratio for catalytic converter
- manage NOx production
- monitor components and circuits
- perform logical tests on emissions systems
- react to the needs of the driver
It's in my nature, you see
Hopefully this little nugget of info helps those who are interested just why computers do things that don't make good common sense. Maximum efficiency and power is never the goal of an engine management system. The conflict with emissions levels puts driving on the back burner and leaves pollution reduction as job one.