Here is the complete explanation on how the Mocal Thermostatic Sandwich Plate Operates:
At low operating temperatures, the valve within the sandwich plate is actually OPEN 100%. This is counter-intuitive for some customers, which is why I wanted to explain it in detail.
Since fluid behaves just like electricity by taking the path of least resistance. By having the passage within the sandwich plate fully OPEN at low operating temps, the oil will actually divert itself into block, by-passing the oil cooler. More oil pressure is needed to pump the oil thru the lines and core than what is needed to simply divert the oil thru the passage in the sandwich plate (back in the engine block).
This serves a few purposes by having the valve operate this way:
1) Oil pressure is still allowed to prime the oil cooler when starting the car
(If the sandwhich plate did not operate this way, it would take until the engine was at operating temperature before your oil cooler would be allowed to fully prime itself. This would cause a possible issue with oil starvation to the engine until the oil cooler lines were filled. This is one reason why it is recommended to prefill the oil cooler as well, to minimize this time in which the engine MAY experience a loss of oil pressure during the initial priming of the oil cooler.)
2) This prevents air pockets from forming within the oil cooler in the event that oil drains from the lines while sitting overnight.
3) It allows the oil cooler core to gradually warm up (at a slower rate than the oil that is circulating in the sandwich plate adapter) in order to prevent any thermal shock caused by significantly cooler oil being introduced into the lubrication system.
Once the oil reaches the predetermined temperature, the valve will close causing the oil to bypass thru the oil cooler core 100%.
The addition of a block off plate is an old school trick used by many. You will see some factory Diesel vehicles even here in South blocking off air flow to their radiators to bring operating temps up. Road Race guys will even tape up their oil coolers during test & tune to dial in their oil temps, bringing them to their optimum range.
Both of these scenarios can be experienced by 370Z owners. Some northern or midwestern Z's located in colder climates will benefit from blocking off the oil cooler during these colder months. In addition, since the weather changes so often throughout the country (especially during the spring and fall), track conditions will change along with it. Some 370Z owners who track their cars may find that experimenting with blocking off varying amounts of the cooler will help them dial in their oil temps. The amount needed to be blocked off will vary on the track, track conditions, driving style, front fascia etc. This is why road racers will use a tape to wrap/unwrap the oil cooler cores an infinite number of times.
The exact oil temp that you want to shoot for varies with the oil grade and type along with the vehicle.
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