Sensor Questions?

[robert dingli]

> its hard to build a non  microprocessor based fi system without
> a maf ;   think about it.
> 

I disagree.  It would be quite simple.  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.

A simple linear mapping between the MAP signal and the injection period 
with injection timed to occur once per revolution works well.  

Injection every ignition pulse tends to magnify the injector dead time 
non linearity.  Low load conditions such as idle tend to be erratic since
the injector pulse widths are close to injector cutoff.

A close look at a typical speed density map will show a relatively
constant characteristic as a function of rpm and a near linear dependence
on the MAP value.

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.  Constant slope fuelling maps work very well.
('76 Celica, ~'87 3SG 2 litre, Wolf3D efi/ignition)

 - Robert

-- 
    Robert Dingli   r.dingli at ee.mu.oz.au
Power and Control Systems    (+613) 9344 7966
Thermodynamics Research Labs (+613) 9344 7712
     University of Melbourne, AUSTRALIA 
**  he who dies with the most toys, wins  **