Hi Ed:
I hate to always appear to be the "stick in the mud" re: the wonderful
"great" ideas that some have to circumvent the $$millions that Mazda spent over
years of R&D.
The concept that creates the most anxiety for me re: my fellow EAA'rs is
the reliance on "racers" (Lynn in Columbus excepted) whose objective is maximum
HP for a very short period of time when our usage is continuous moderate HP over
a very extended time. The issues and constraints are very
different.
My research into OEM irrigation engines shows that they last from
25,000-30,000 hours TBO producing approximately 0.5 HP/cubic inch at 24"-26"
MAP. Most run just off WOT at 1,200 - 2500 rpm depending upon
size.....bigger slower, smaller higher rpms. I recall that I calculated
mean piston speed for several and that seems to be the key issue which
determines "specified" rpm. Even when one reduces the TBO by the
cube of the rpm which we desire to use to account for higher BMEP and
rotational forces (squared function), the TBO still comes out to in excess of
3,000 hours, if someone doesn't muck with the "complete"
system.
The point: OEMs have spent $$millions to insure these engines will
produce SPECIFIED HP under an unbelievable range of difficult conditions.
Why would one want to add any single element which would negate that
effort?? Make it produce more HP....of course, but all durability
expectations are Null and Void. Make it produce less HP for longer....of
course, but the price will be high and again, even though more $$ will have been
spent, the expectations are a SWAG....and from my experience, a very poor result
is a high probability.
The 13BT will produce....what 250 HP as specified by Mazda???
That means as designed, it will cool adequately, will function over a large
range of conditions at maximum efficiency at 250 HP. Why would we be so
arrogant as to suppose that we can improve upon that, and for what
reason?? Do not even guess,....that 13BT was run at WOT for many
hours at Maximum HP without failure.....and even worse was cycled back and forth
from max torque rpm WOT to max HP WOT, dumped to idle then back to max HP,
etc....on and on and on! There are hundreds, if not thousands of
combinations of the various components which over hundreds of thousands of hours
of R&D are continuously refined to successfully pass these tests. I'm
certainly not smart enough to know how to improve upon that. Perhaps that
is my issue?
If I'm not mistaken you have written a bit on this and have endeavored to
follow "change as little as possible of the major components" as one of your
guidelines. Remove the emission components? Seems OK! Change
the plug wires, perhaps? Change the waterpump when we run at less that max
"specified" rpm? That makes zero sense to me. Change the rotor
seals/materials/oil pump/waterpump/oil flow.......??, go ahead....but pain hurts
like ____, and my insurance rates go up when an EAA'r crashes and kills
themselves!
Pardon my passion in this, but too many "experimenters" are ruining the
possibility of success in the use of low-cost, high production, automotive based
engines in aircraft and it is a shame because there is no fundamental reason
that today's modern automotive engines won't perform admirably, IF utilized
properly. Work on the installation, not on the basic engine.
Installed in this manner, the accessories will be the issue, not the
powerplant.
IMO for your engine.....Best: buy some new rotors designed for your
housings. Next best: Buy three wreck engines with relatively low
mileage ($300/ea. around here) and measure and pick a rotor which meet Mazda
specifications. Last and probably best and least expensive in the long
run, go purchase an RX8 from a rear-end wreck and put it in, Stock
innards/major components.
Keep up the super work and communication. We are counting on you to
be successful. Your latest escapade really threw water on my excitement
re: my project. I had hoped you would process fuel like crazy for a
thousand hours while we watched your R&D/durability results from our
shops!!
Continued good luck and POR,
Doug in Colorado
In a message dated 4/14/05 8:35:12 AM Mountain Daylight Time,
eanderson@carolina.rr.com writes:
Hi Doug,
Some good thoughts and questions, of which I would like to know the
answers to as well. I believe the reason the experts are recommending
milling the RX-8 rotors for the older seals (when used in the older rotor
housings with peripheral exhausts) is that the RX-8 seal was not designed to
withstand the forces of crossing the exhaust port (in the Peripheral wall)
opening unsupported. Its rather skinny and long. Mazdatrix reported
the RX-8 seals warped as a consequence of the the hot exhaust gas blowing over
them and primarily the lack of wall support at the exhaust opening(on the
older housings). The combination of the additional heat and lack of wall
support appears to be more than the 8 seal can take.
However, I am in basic agreement with you why machine the rotor
when perhaps a new/modified seal is the answer. I want to check with
Tracy Crook since his seals are reportedly 800% stronger than stock apex seals
to see whether the seals could be machined down/created so that they fit in
the RX-8 rotor standard apex slot and still be strong enough - say 300%
stronger than stock {:>). Since they are not made of typical "gray
iron" alloy that the stock and most other seals are made and chill/case
hardened, they may be amenable to machining.
Yes, having airports scattered around in just about every county and
sometimes three or more in a county, the geography is much kinder to
engine-out excursions here on the east coast. Fly High, Glide
long! Better yet, keep running on both rotors.
Ed A