Equations, Equations and more equations.

[Jeffrey Engel]

Jens Stobernack <jstobern at acs.ucalgary.ca wrote:
> 
> I've been reading this list for awhile now and was wondering what
> equation you are trying to solve when using a computer to run your
> engine.

Because of the non-linear nature of the IC engine, most folks use 
lookup tables.  The function tables are also easier to reprogram when 
significant changes are made to an engine.
 
> Essentially you are trying to determine when to fire and how much fuel
> to deliver.
> 
> What I've gotten sofar is that
>     - O2 readings regulate mixture.

The O2 sensor is really feedback.  It lets the computer 'know' how 
well it is doing using the lookups.  If the mixture is off, then the 
computer can add or subtract a 'fudge factor' to get the mixture back 
where it needs to be.  The O2 sensor is only used during closed loop 
operation.  Most cars go open loop at WOT and the computer ignores 
it.

>     - Knock and RPM control timing.
>     - MAF or MAP readings control fuel delivery.

The MAF measures the air mass going into the engine, the MAP 
typically uses air temp and barometric pressure to derive the air 
mass.

> Can someone publish the formula(s), the variables and what type of
> sensor is used to determine that value?

>From what I can tell, most of the data is determined empirically.  
The big guys use dynos and big $$$ instruments.  The rest of us read 
plugs a lot and use the seat-of-the-pants dyno.

> Thanks alot for you time,
> Jens

A pleasure.  Just remember how much you paid for this information 8)

 
je
jengel at fastlane.net

     "I can resist anything but temptation"
                                  Mark Twain