<911> Bosch Motronic -Forward -Reply

[Mark Boxsell]

At 12:44 PM 20/02/96 -0800, you wrote:
>In a recent post, I had gotten a response back about the temperature
>sensors NOT being linear.  Listed below is the response I had to this post
>from my friendly (and quite knowledagble) Alfa mechanic.
>
>Serve ...volley  ...volley  ...???
>
>>Brad, the temperature sensors Bosch uses are thermistors and in all
>>the testing I've done with them, it sure as hell looks like they're linear. 
>>And even if they are not, adding a fixed resistor of whatever value
>>simply starts the base at a little higher value and goes on from there. 
>>The object is to have the ECU understand that the engine temperature is
>>a little colder than the sensor says it is so it will be rich enough to start
>>easily and run smoothly if that proves to be the problem.  The use of a
>>TrimPot tells the story.  
>
>>I can be wrong, others can be wrong.  Please let me know what you
>>find.
>
>Further opinions anyone?
>
>Brad 
>'86 Porsche 911 Coupe
>'91 Alfa Romeo 164
>
>
>

Brad,
          If you have a look in some workshop manuals you should find the
graph for these sensors. Anything from Toyota to Volkswagon (anything L or
LH Jetronic based) all have the same temperature curve. (Something to do
with the Bosch manufacturing licence I would imagine).
The sensors are not really linear but with a basic system you would probably
get away with it (for coolant temp).
                        
                regards,
                                   Mark Boxsell
                                   MRB Design.