Bosch Motronic Questions

[WERNER_HAUSSMANN at HP-Loveland-om2.om.hp.com]

The Bosch Air Meter is a vane that is hooked to a logorithmic 
potentiometer.  The output is usually in the form of two voltages.  One 
voltage is fixed, the other is from the potentiometer.  The ratio of the 
two voltages gives air flow. The vane changes the air stream cross section 
area to get air  flow.  There is also a thermistor to measure temperature.

Changing the spring force will change the output voltage by approximately a 
multiplier for the range of the meter.  Changing the screw adjustment of 
the meter will offset the output by a fixed air volume amount (much affect 
at idle, little at WOT)

You can also change the calibration of the meter by changing the value of 
the fixed resistor.  Some meters (non-bosh) do not have the fixed resistor.

Using temperature, air flow x time for volume, and athmospheric pressure 
(may or may not be measured), the air mass is calculated with an analog 
computer (L-Jetronic), or digital computer (Motronic).

If the air meter is  used as an air flow device you cannot use the 
resistance of the potentiometer, you must use the voltage to get any 
accuracy.


Werner

______________________________ Reply Separator ________________________________
_
Subject: Re: Bosch Motronic Questions
Author:  Non-HP-owner-diy-efi (owner-diy_efi at coulomb.eng.ohio-state.edu) at 
HP-ColSprings,shargw2
Date:    6/19/96 12:45 PM



> 1) I've been told that it is possible to lessen the spring force on the door 
> of the Air Meter by moving the spring back a few notches, which may
> somewhat lessen the throttle lag issue.  I've tried to get to the spring by 
> removing the bottom plate of the meter, but apparently access to the
> spring is from the top.  My question....  How do you get the black plastic 
> top off without destroying it in the process?  I'd also be interested in
> hearing from anybody who has experience with this modification.

I thought vane meters worked by correlating the momentum of a stream 
of air against the rotational position of the vane.  Doesn't changing 
the spring force alter that relationship?

Sorry, I can't help on the disassembly question.


Anthony Tsakiris

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The opinions expressed are my own and not necessarily those of my employer.