I am dealing with oil temp issues and some testing methodology. I got to thinking what oil is actually being measured. I lifted the pic's below from one of Dan's posts. The O/T probe is sitting in the upper chamber (2nd pic) where the oil comes directly from the oil pump feed gallery. When the Vernatherm is open, the oil if flowing into the second chamber and then to the filter. I should have accurate results for oil sump temp in this case.
However, when the V/T closes and blocks the passage to the second chamber, forcing oil in the oil pump output gallery to follow another path to the oil cooler, there will be zero flow from the first to second chamber and the oil in the first chamber will be stagnant. Unless there is some type of relief built into the chamber design, it is unclear what the temp of this oil represents. In theory, there would be no mixing with the fresh oil flow through a different part of the oil pump feed gallery. It would seem that this stagnant oil would ultimately pick up the temp of the surrounding housing, which in theory would be based upon the temp of the oil returning from the cooler.
This seems like a strange design. You get oil sump temp with V/T open and post-cooler temp with the V/T closed, though it does tell you exactly what is being fed to the engine. However, in the latter case, you are dependant upon in indirect reading. Further, if are using the plunger, there would be no oil in that chamber and your now measuring air temp, presumably matching the temp of the housing, presumably matching the post-cooler oil temp.
Am I missing anything here? Does anyone know if there is a relief hole between the chambers to maintain some type of flow? If that were the case, I would be reading sump temp and not post-cooler temp with the V/T closed. It would seem to me that the sensor belongs in the second chamber.
Larry
However, when the V/T closes and blocks the passage to the second chamber, forcing oil in the oil pump output gallery to follow another path to the oil cooler, there will be zero flow from the first to second chamber and the oil in the first chamber will be stagnant. Unless there is some type of relief built into the chamber design, it is unclear what the temp of this oil represents. In theory, there would be no mixing with the fresh oil flow through a different part of the oil pump feed gallery. It would seem that this stagnant oil would ultimately pick up the temp of the surrounding housing, which in theory would be based upon the temp of the oil returning from the cooler.
This seems like a strange design. You get oil sump temp with V/T open and post-cooler temp with the V/T closed, though it does tell you exactly what is being fed to the engine. However, in the latter case, you are dependant upon in indirect reading. Further, if are using the plunger, there would be no oil in that chamber and your now measuring air temp, presumably matching the temp of the housing, presumably matching the post-cooler oil temp.
Am I missing anything here? Does anyone know if there is a relief hole between the chambers to maintain some type of flow? If that were the case, I would be reading sump temp and not post-cooler temp with the V/T closed. It would seem to me that the sensor belongs in the second chamber.
Larry
Last edited:
