[T2] electronic thermostat

[Robert Mann]

Christoph,
	I chime in early from the viewpoint of not only a digital 
ignoramus but also a digital reactionary.
This hobby-pioneering may lead to a useful new set of functions on a 
VW, but the first Q is whether just the first function, 'thermostat', 
justifies this complexity and large set of very rare failure modes.
	I happen to know v little of the std thermostat, but surely 
we need informed opinion on how defective it is.  What failure modes 
does it exhibit, and how often?  How difficult are they to fix?
	Then, supposing such preliminary Q's about NEED are answered 
or disregarded, I have a couple suggestions:-

...

>  I suspect that since air is a great thermal insulator, most of the 
>heat received by the mechanical thermostat will come trough  its 
>metal mounting bracket which is attached to the engine.

	I'll bet that way too.
	Of course, you could use a special, much more insulating, 
mount.  But it may not be easy to arrange for the passing air T to 
dominate the sensor.


>I probably will have to take care of that while programing point 2)

	Some limits may exist to this method, no?

>
>Now , I also have this other idea. Instead of using the thermostat 
>bracket to hold my temp sensor , I can install an (none contact) 
>infrared temperature sensor just on the top  of cylinder III (by 
>drilling a small hole trough the tin to accommodate the sensor) and 
>use that temperature to control the flap. In this event what, should 
>be point 2) ???. I like this idea because I the control of the flap 
>will be the reflection of areal  cylinder temperature. I can also 
>attach an LCD display to my Arduino to monitor real time the 
>temperature and even put an alarm using a buzzer in case the flaps 
>stay open too long , I also wont need any thermocouple temp sensor 
>attached to the spark-plug anymore.

	It is not apparent to me how the system you're developing 
could substitute for a thermometer (e.g. a thermocouple, as many of 
us have) in intimate thermal contact with the cylinder head 
(conventionally, #3 cyl which usually runs hottest).

>
>Also , arduino has an endless possibilities , I would like to use it 
>as a mini computer for my bus later on .
>
>If you guys dream to add something to my project , what would it be?

>I plan to check the voltage

	do you mean the voltage across the main battery?


>, RPM

	slap a tape-recorder head in where the flywheel teeth go past it;


>, oil temp

	what is the price of your digital T sensor?  I bet it isn't 
as cheap as the meat thermometer which I have substituted for my 
dipstick  -  a thermocouple in an oilproof tube


>, cyl temp

	as I say, it will matter where this is sensed

>, etc ....

	perhaps you can slap in a knock sensor and use it to keep the 
ignition timing advanced to just short of knocking (Saab took to 
doing this at least 20 y ago).


	Computers rule not OK  :-P


-- 
Robt Mann
Whangaparaoa, New Zealand
'73 VW 1600dp Devon camper
'53 Meteor V8
various Jawa-CZ and Jawa-NZ strokers