Tracy Crook wrote:
Andrew Mueller wrote:
Sorry Guys,
The heat strips I talked about in an earlier letter should go on the
outside
of the inner water seal closer to the water jacket and should only be
used
on engines that require the seals to be placed into the aluminum
rotor
housings (1986 and newer 13B rotaries).
Thanks Leon!
Andy
This is a bit confusing. ALL 1986 & later 13B have the oring seals in
the
side housings, not the rotor housings.
Tracy Crook
rws@altavista.net
www.rotaryaviation.com
Thanks for catching that Tracy. Also I have not seen those heat strips for
years.
Back in the 70's I think they were used. I also think they were on the
combustion side of the O-rings. Makes more sense.
Paul Lamar
Leon Promet wrote:
Hi Paul,
The comments on the "protector strips" on the newsletter seems to indicate
some considerable confusion. So I'm sort of wondering where you guys get
your info? If you are correct about them going on the combustion side,
then Mazda has been telling us the wrong story for nearly 25 years, and
I've been assembling engines incorrectly since the strips first became
available. Indeed, I very quickly found (much too my great embarrassment
and cost) that engine life and durability is shortened if they are
installed the way you suggest.
That is what made me finally read the instructions!!. I can still hear the
words of my mentor ringing in my ears:
"Leon, ... when all else fails, READ the instructions!!"
So ever since, anyone I am training gets asked the question (with me
holding up a protector strip):
"What do you think this is for??"
The next question is: "Where do you reckon they go??"
The third question is: "Where do Mazda say they go??
The fourth question is: "Who's correct??"
The final question is: " "Why??"
So here's the definitive answer.
Mazda are magnanimous enough to put the instructions for use inside the "O"
Ring kits (1757-23-040B etc). They tell you to put the protector strip on
the water side of the "O" Ring with the concave side facing the "O" Ring.
The "O Rings sit proud of the grooves, but when compressed, doesn't
fully fill the grooves themselves for whatever reason, Mazda in their
wisdom decided. So the purpose of the "protector Strip" is not to shield
the "O"Ring from the combustion gases. It is designed to push the "O" Ring
into intimate contact with the side of the groove CLOSEST to the trochoid
and the combustion gases.
Just as in Piston engines, the gas sealing is done by a metal to metal
interface which stops the combustion gases getting into the water jacket.
(If you don't believe me, have a look at an NSU Ro 80 or Suzuki RE5 rotor
housing. NO "O" Rings except for the smaller ones around the water
passages far away from the trochoid!!).
The "O" Ring is simply there to stop water leaking INTO the combustion
chamber once the engine is switched off!!!!! If the rotor housing is
warped from overheating, the gases can then get to the "O" Ring and burn
it. No little thin piece of aluminium strip is going to stop it. They you
get a water injected Wankel, and eventually a steam engine.
I don't happen to have a 1757 "O"Ring packet at hand right now, but I made
a particular point of this in an article I wrote way back in 1990/91 for
Fast Fours & Rotaries Magazine. The article I wrote even included a photo
of the instruction sheet because this is an incredibly common
misconception. (I'll post the article when I get hold of another a copy).
The "protector strips" are NOT heat shields. If they were, they would be
made out of stainless steel, not aluminium. They were specifically
designed for use in the EARLIER version engines up to '85 where the "O"
Ring grooves are in the aluminium rotor housings. The late model engines
('86 ~ and LATER), which have the grooves in the cast iron side housings
DON"T use them any longer as the "O" Rings are designed to completely fill
the grooves when assembled (unlike the earlier groove in the rotor housing
models).
The "O" Rings in these LATER model engines are also of substantially
thicker section and are NOT interchangeable either way with the earlier
model ones. The grooves, being slightly deeper, will also not compress
the strips, so they are not necessary, are useless because they don't
compress, and could also be detrimental. I haven't tried them in the late
model engines, so I don't know if they are detrimental, but I certainly
have no intention of experimenting either!
So before you post this on your newsletter, can I ask you to firstly have
a look at the instruction sheet inside a 1757 "O" Ring kit. Ask yourself
questions 3, 4, and 5 above, and confirm that I am not off my face on
recreational narcotics or magic mushrooms. If you can then see that you are
indeed mistaken, may I ask you then to please correct this error of fact
on the newsletter.
Sincerely,
Leon Promet
OK Leon I guess my 25 year old memory was fuzzy.
I think I see what is going on here.. finally. The ones I was referring to went near
the combustion chamber in the old days. Apparently those are no longer used.
I just checked the Haynes manual for 1986 through 1991 and they are used adjacent
to the *** exhaust port *** on the outside of the o-ring?? However the picture,
page 28, in the Haynes manual shows them adjacent to the intake port near the
inner O ring. The Haynes manual also does not say inner or outer o ring. Just says
"outside the O ring". I will scan this picture soon. More on this when I get a bit
more time.
These pieces are not mentioned at all in the 1994 official Mazda Work shop Manual.
I guess they are not that important and are no longer used. Perhaps they changed
the groove dimensions or the size of the O-rings.
Paul Lamar
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