Introduction from Perth, Western Australia

[Bernd Felsche]

Mike writes:

>Hi chaps,

Goodness - that makes at least three of us within shouting range.

Could this be growing out of desparation due to isolation? :-)

>In 82 my project thesis for Western Australian Institute of Technology was
>to do with EFI and transmission control. Some work was done on a 72 ford
>escort (4 cyl 1300 side cam bowl in piston flat head crossflow n/a). Used
>the original inlet manifold, cut to take bosch injectors off a 2L combi using
>clips from a chrylser, soldered fuel rail, AFM of the same 2L combi (flap
>type - yuck). ....

[snip]

>My main interest is to install my own EFI to replace the existing bosch
>unit but in the same housing so its a drop in replacement - except for a

That's the reason I want to do data acquisition first.

>daughter board to take extra injector, water injection, laptop comms,
>security and other nice additions.

>At moment I'm curious of best conversion resolution for hot-wire AFM, I've
>seen the 8051 projects with 8 bit resolution, I thought 10 bits would be
>more appropriate for multi-point as a minimum - can use an SPI 12bit and
>wonder if there are any comments on best AFM resolution. Oh incidentally,
>the output from my bosch (exisiting) AFM is log. ie. Quiescent at around
>1.6v then rises logarithmically to around 5v at maximum load - anyone
>have any observations on this type of AFM and practicality of using log
>to linear i/p conditioning with their EFI front end ?

Logarithmic is good because it gives you "better resolution" at, and
near idle speeds. You detect the significant changes more accurately.
Don't fight it - go with the flow. :-)

You can set up a table to aid in the conversion of AFM output to
massflow. Interpolation can be done fairly quickly so not all
possible values need to be stored... otherwise with 10 bits you'd
need 1024 pairs of values -- do a hash lookup, dividing by say 32
will give you only 32 pairs of values. The log-linear table will by
its nature provide better quality numbers at the low end of the
scale.

Note that the airflow is unsteady in practice anyway; the meter
output should be taken with a grain of salt. Use the feedback from
the O2 sensor to close the control loop.

I assume that you've read all the available Bosch documentation on
the metering process. Do you have (access to) a flow-bench?

The Bosch successor to L-Jetronic (flap-type) was effectively
Digifant (aka L2-Jetronic). It uses the "same" flow meter. ADC is
8-bit as far as I can tell. Interestingly, the flow meter output is
supposedly linear with flow-rate to simplify the task of the ECU.
I'm not planning to reverse-engineer the puppy because I'm
restricting my exposure to published materials in the public domain.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
	http://www.perth.dialix.com.au/~bernie - Private HP
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