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