The only reason I bought the turbo is I'm waiting for the compound. I
don't care about the supercharger end of it. Karibian

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Spoken like a man with more flying hours behind a turbo compound engine
than anybody else I know :)

Here is the latest cutaway. Almost ready to go into the machine shop.
Oooo good thing I did this one. I just noticed a mistake.
Thank goodness for 3D.

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Fixed the problem and added the gears.

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Did I luck out or what? I was wondering how I was going to adjust
the V belt tension as the traction drive box must be coaxial
with the turbo charger. Due to my extremely fortuitous choice of
parallel shaft reduction gears all I need do is make this simple clamp/
mounting bracket. You rotate the whole unit until the
belt has the proper tension and tighten the clamp bolt.
Whew! What a relief :) (Last 3D.)

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Major iteration #4. Time to fire the engineers (me) and put it
into production. It is getting so  I can completely redesign this
thing in 48 hours :) I moved the one way clutches to the output
shaft from the intermediate shaft so the engine would could not zing the
2nd stage reduction herring bone gears. I also picked up an inch more
clearance for the compressor air intake of the stock Mazda 2nd gen Turbo II
RX7 engine.

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Here is a transparent 3D of the box. The shaft on the left is always going
at a speed directly related to the turbine so it can do double duty as a optical
turbine tachometer. That is why there is access to it from outside the box.

I have been thinking about this and I think that 99%
of the time when the engine is running at a constant speed the turbine
RPM (geared down by the box of course) will be potentially greater than
the engine RPM. This will be very true when a car is cruising down the road
in sixth gear at 3000 to 4000 engine RPM. I think the over running clutch
incorporated in this version of the gear box effectively serves one or two
functions of a variable ratio box. I would not be a bit
surprised if this box alone improves the steady speed MPG of a RX8 engine
in the range of 70 to 100 MPH. If so it will also improve the acceleration
in this speed range as the turbine is adding its torque to that of the engine.

To quote Scania from their web site:
"Scania turbocompound;"
"Turbocompounding creates extra power by converting "wasted" energy."

"Turbocompounding seems to defeat the laws of physics by creating energy out
of nothing. It works by recovering energy that would otherwise be lost, or
wasted. It is a classic example of recycling. Instead of expelling "wasted
energy" via the exhaust pipe, more heat is extracted from the exhaust gases."

"Stepping down the revs produces a useful boost in torque, which when reaching
the flywheel adds momentum. You get this extra driving force without
increasing expenditure on fuel."

"The economical green band on the rev counter provides a wide range of
economical engine speeds, making life easy for the driver. The engine
exhibitsXgreat flexibility. The rotation of the crankshaft benefits from the
constant extra drive coming from the turbocompounding process, helping to
even out the rhythmic pressures induced by combustion. So the engine runs
more smoothly."

Of course the importance of this MPG improvement cannot be over stated
in light of the world wide oil problem. The rotary is 5% worse than a piston engine
but the turbo compound feature has the potential to make the rotary 15% better than
a piston engine. That is a monumental improvement in engine efficiency not to mention
the simplicity of it and the intrinsic high power to weight ratio of the rotary engine.
(Not fully exploited yet as Mazda is still building mostly cast iron rotaries while
the rest of the world has switched to aluminum blocks.)

This is as close to a 100 MPG carburator as we will ever get.

It can't be done however with a four cycle piston engine because of the exhaust
valve losses and valve durability issues.