Can anyone enlighten me as to the flow scheme of the two oil coolers on the US spec '8?

1 - Does the whole flow from the pump go to the coolers before being sent to bearings? or a slip stream?

2 - Is the flow split between the two coolers? or thru one then the other? (i.e. series or parallel?)

3 - Before or after the filter?

Thanks for any info you can contribute,

S

 

I'm not totally sure about these, but I'll note my certainty in each one:

1. The whole flow goes through the coolers. I'm pretty sure about this. The oil comes out of the front cover direct from the pump, and then flows through the coolers and then re-enters the engine on the rear housing by the oil filter. NOTE: There is a most likely a thermostat in the system, too. The aftermarket thermostat on my RX-7 (not a Mazda part) simply opens a "short circuit" path to skip the coolers when the temp is low. I'm not quite sure how the Mazda oil thermostat works, but it seems reasonable that it uses a similar approach. The stock thermostat was integrated into the cooler on the RX-7.

2. The flow is in series on my aftermarket setup, and I think the R1/2 dual cooler setup on the RX-7 was also series. The RX-8 is probably series, too.

3. The coolers are before the filter. The oil doesn't go through the filter until it re-enters the engine on the rear side housing or oil filter pedestal. I'm not sure which it is in the '8; some RX-7s had the oil enter the rear side housing and others (like the FD) had the oil enter the oil filter pedestal (which is bolted to the rear side housing). Whatever the entry details on the RX-8, it seems very likely that the filter comes after the coolers, since this was true on all of the RX-7s.

-Max

 

Interesting. I would have though you'd want to filter the oil first. Both to keep crud from accumulating in the filter passages and also to reduce resistance (filtering colder oil). Also, if the thermostat is integral to the cooler, or in the path, wouldn't you be bypassing the filter as well with thermostat shut?