George Lendich wrote:

Paul,
I'm wanting to know if anyone has an understanding of the oil passages of the RX8.

The RX7 has a return to sump, of the Rear (our Front) housing which is a rather large passage taking the oil from the Rear ( our front) Rotor bearing.

This is in exactly the same position of the RX8 exhaust port and would require the oil return passage to be moved. Also I don't think they would have the oil to sump return so close to the exhaust
port, rather I would think they good water cooling in this area.

As this is a somewhat difficult position to machine a oil return passage in an aluminium housing - I thought the RX8  arrangement might give some clues to an alternative oil return passage.

I know this is a hard one, but someone might by now have an understanding of these inner workings.

George ( down under)

Looking at the rear (car) cut a way end housing you are right. The oil does indeed drain down through
the area where the RX8 side port now resides. My guess is Mazda put it there on the 2nd gen
as that was the coolest place for it. Going straight down might cause more heat transfer
to the oil. However from the looks of the small size of the oil drain back oil in the rear main
bearing insert you won't need a very big passage. It is rather surprising the casting
itself has such a large rectangular channel. You do need of course a place for the water
to get by it from the hot side towards the cool side.

Looking at the RX8 rear end housing cross sectional view it appears Mazda has totally
redesigned the water passages. It also looks like they added volume to the area around
the rear main that holds some drain back oil. I have no idea how the oil gets
from that space down to the oil pan. Perhaps looking at the back of an RX8 rear end housing
might help.

Paul Lamar
 
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