So.....since the rotors weigh the same within measurement error, the
ability to rev to the 9,000s range vs. 7,000s range is not related to the
orbiting mass of the rotor. (Note: the motion is NOT truly circular,
it is an epicycloid path that the center of mass of the rotor takes.
That 10 lb. rotor flops around plenty (technical term) and 10 lb. is lots
heavier than an aluminum piston!
It is apparent from an article on the "other" site, that the wall
thicknesses and casting detail are lots more refined on the RX8
rotors than on earlier models...for more uniform and desirable heat
transfer and uniformity.....oil cooling the rotor, etc.
The mass being basically the same, it becomes a high probability that
since centripetal force is F = (Mass x rotational velocity
squared)/radius of rotation, {F=(m x w^2)/r}, it must be the
weight of the seals themselves that are the
critical element? The force at 8,500 vx. 6,500 is (8.5/6.5) squared
or 1.71 times greater. Might this be why seal wear on the original
seals goes up substantially at around 6,500 rpm?
Tell me....why would one increase the depth of the seal groove of an
RX8 rotor to allow a heavier seal???? On the RX8, 3.25mm/9.5mm
=> approx. 34% reduction in apex seal mass!! A lighter
seal means a whole lot less force of the seal against the housing at
8,500 rpm!! Anyone want to go back to old seals and rev to 8,500
rpm?
Note: the seal force against the housing at 8,500 rpm on the
RX8 is still higher than the old seal at 6,500.... (.66 x 1.71 =
1.129). Not much more, but there are probably even more very
small details that we are not at first glance able to know and
understand? Seal material/housing material compatability is probably
one significant factor?? (I used 9,000 vs. 7,000 and the numbers
still come out about 10% higher seal force on the RX8, even with the
lighter seals.)
Having been an R&D engineer at FoMoCo, it is hard to explain to
most persons the creativity, detail, imagination, trial and testing and
testing and testing and testing and ...... which goes into making an
engine acceptable for production in quantities of XXX,XXX's and
higher. (One simply can't be wrong...it could bankrupt even the
largest OEM.) And....those Mazda engineers have done what many OEM's
gave up on many years ago. How? Through their persistence and
incredible insight into the issues.
Before one gets the wire EDM out and starts going counter to what
Mazda no doubt spent many $$$$ (more than all of our annual incomes
put together??) on how to increase HP in an RX8, more information is
needed before we start mixing and matching just because the
parts will fit. I know we are experimenters here, but lives of
some who may not understand the "physics" limitations will ultimately
be at stake.
Above all: Just because something works for 100 miles in a
sprint race DOES NOT mean it will work
while hummmming along for 5 hours at a crack at 75-80% max. HP on a
cross-country over and over and over again....hopefully. So far, my
Lyc is a piece of 30's era design and materials...but it has run for 2,000
hours (350,000 miles) at 75-100% without fail!!
Most of us aren't as lucky as Ed and his "on airport" emergency
landings. Perhaps it is that his green carpet (Carolina's) is
lots more friendly than our granite peaks out here?
Doug in
Colorado