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

Thanks Paul,
All that info and drawings are most helpful.

I've got a feeling that there is more oil being collected here than we
imagine, perhaps from the side seals - hence the large collection area.

I will keep working on it- where's Butch when you need him.
George

The side seals are keeping what oil escapes from the rear main bearing
on this side of the rear rotor from getting into the combustion chamber.
This oil also lubes the phasing gear on this side of the rotor in the process.
I think a little restriction in the drain back might not hurt that much.
In other words I think the side seals could handle a bit more oil pressure.

The vast majority of the oil is squirted up into the rotor on
the other side of the rotor and drains back down to the pan in the center housing.

Paul Lamar

 
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