What is really needed is a reduction in fuel burn. If a 20%
 reduction in fuel burn could be achieved than people would be
 more likely to spend $25,000 on a rotary engine to replace their
 aircraft engines. This is most easily achieved by turbo
 compounding. To turbo compound all you need is a modified turbo
 charger and a gear box to feed power back into the front of the
 e-shaft.


 Paul Lamar

Paul

The exhaust does not get sucked from the rotary engine. Therefore there is a
contaminated fuel burn.

It appears that the interior exhaust port of a 13B Mazda engine is the same
as a 1 1/4" ID pipe diameter. Common sense tells me that the exhaust pipe or
manifold should not exceed this diameter. If possible the diameter should
diminish to compensate for the exhaust cooling in the pipe prior to exiting.
As there are no valves the exhaust flow would suck the contaminates from the
engine and also cool it.

Cheers

Ken

The exhaust does not get sucked from any engine. There is always
a residual pressure above atmospheric pressure on average in the exhaust of any
internal combustion engine. The rising piston forces the exhaust gases
past the exhaust valve not to mention the high residual pressure.

Any engine with valve over lap has a considerably contaminated fuel burn.
It is really high on a 2 cycle engine. Even a non valve overlap engine like
the side exhaust RX8 rotary still passes on some residual exhaust gas.

What is your reasoning  for a 1.25 diameter pipe?

I can see at certain power levels and certain RPM's a 1.25" dia. pipe might
be better than some other diameters due to organ pipe tuning effect
momentarily reducing the pressure at the exhaust port when it opens.
I suspect that would happen at some lower power levels.

I am unaware of anybody doing any studies on the optimum diameter AND simultaneously
the optimum length of the rotary exhaust. I am sure that has been done on piston
engines. The only rotary data I have is a study that Mazda did on the optimum
>>> LENGTH <<< alone of the exhaust pipe. Here is is.


I notice
that Star Mazda racing RX8 rotary engines use a very large exhaust pipe.
My guess is the down pipe is about 3  inches dia. That is an area of 5.65 square
inches. The connecting pipe from the port to the 3 inch diameter down
pipe looks to be two inches dia. or 3.15 square inches each. A 1.25" dia. pipe
would be only 1.22 square inches.

There is always a higher pressure differential on the exhaust than
there is on the intake and therefore  the aerodynamic design of the intake
is much more critical on how much HP the engine will generate.

I was pleasantly surprised that the side exhaust ports did not hurt the
power on the p-port RX8 engine as much as I expected.

If your implying the combustible mixture is contaminated in the rotary and
that is the reason the fuel burn is 5% higher I disagree. I think it has mostly
to due with how, when and where the fuel is ignited and the surface to volume
ratio of the moving combustion chamber to a lessor degree.

Paul Lamar