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grant
By the way, i already have a spacer between my block and sump - its part of most deep sump kits, including Pedro's.
The ODB2 idea is interesting - i wondered about that too, and am curious if anyone has practical experience "buy this, it works"
I need to ask Gene (engine builder who finished the job while i was in France working and drinking, generally in that order) what senders he installed - One question is "why can't the factory pressure sender drive two gauges?" Ditto for the temperature.
Grant
The pressure and temperature sensor each supply an analog voltage signal to the DME and its AD converter which converts the voltage levels into digitial values, say something between 0 and 255. (The temperature sensor digital value might require an offset, say -40 (C) so a zero reading would be interpreted as "-40C".) This digital value then can be packaged up in a CAN message and sent to the cluster controller which converts the value back into a voltage level which then drives a gage.
With the proper electronics this info could be used to feed any number of gages with the info.
In the Boxster, at least in my Boxster, the oil pressure is just used to know the oil pressure is not too low which keeps the low oil pressure light off. I'm not sure if the DME is responsible for the low oil pressure warning light directly or if the cluster controller handles this. Either the DME sends a CAN message to the cluster controller to turn on the light in the event of low oil pressure or it sends the actual oil pressure -- in digitial format -- and the cluster controller then processes this to know if the oil pressure is ok or not. At the cluster this provides a relatively painless way to make this low oil pressure level threshold a value that can be rather easily changed vs. having to flash a change to the DME.
The temperature sensor value may only be used internally by the DME to compensate/adjust the oil level reading though by my observation over the years with my Boxster the oil level varies with temperature. Because I park in the same spot at home I can check the oil level in the AM with the engine cold and note the level. After a drive that gets the oil fully up to temperature I park the car in the same spot. Sometimes I return to the car with the engine still warm even hot and check the oil level and it is up by 1 to 2 bars depending upon how cold it is in the AM.
I haven't delved too deeply into what's available on the CAN bus. My automotive test tool work was focused on generic data that was well documented and available from all OBD2/EOBD/JOBD compliant vehicles.
It doesn't help matters at all that Porsche does not provide any details on what bus traffic is present or how to perhaps navigate through any gateways to obtain this info. (It is obtainable after a fashion by other means. For instance, when I had my new 2008 Cayman S in to get the service light extinquished I captured all the bus traffic that arose from the Porsche diagnostics computer doing this. I had plans for doing a Porsche specific OBD2 data logger but shortly after I captured this bus traffic the Cayman was destroyed in an accident and I lost all enthusiasm for doing anything more in this area.)