Joe;
I’m not sure this is helpful;
because I’m drawing on those weak memory cells from about 6 years ago;
but I recall a seal washer that went between the diffuser flange and the bottom
of the injector (or injector housing of the fuel rail). I think I was
short one, and the others not in good shape, and IIRC, I got new ones from the
Mazda dealer parts dept. On an invoice in my file they are listed as an “insulator”
Part # N3A1-13-257. Unfortunately; I can’t assure that it is the
part you need. They must be used on a 2 rotor because I got a set of 2 and 1
special ordered. These seals were used with the original diffusers.
I bought my fuel rail (with injectors) at
that time from SR Motorsports, 915-516-7382. There was a guy there then
that was very knowledgeable about all these parts. Perhaps they could
help you with the proper seals and diffusers.
I also recall getting 20B parts from Mazda
through a service center here in SoCAL that sold to racers using 20B engines.
I can’t find anything in my file, but it was Mazda Speed, or Mazda
Performance, or something. Some of our racing friends must know - - Lynn? Call Racing
Beat; they should know.
Isn’t there also a seal at the top
of the ‘hole’ in the rotor housing that seals the fuel rail so no
air would leak in there. It is even possible that those are the ones I
replaced.
Maybe this helps,
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Joe Ewen
Sent: Monday, September 03, 2007
7:33 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Interface
between Primary fuel rail and diffuser (air bleed) 20B
When installing the primary
fuel rail on my 20B, I noticed a gap between the primary fuel rail and the
diffuser (air bleed.) One of the original air bleeds was damaged when the
rebuilder was removing. He could not locate a replacement. He
supplied new air bleeds designated for a 93-95 13B, which he was informed were
usable in the 20B. The gap between the fuel rail and the diffuser seems
to be between 0.110" and 0.145". This measurement was
determined by inserting the diffuser and measuring its depth. Then the
fuel rail was bolted in place. Through the intake port, the injector was
pushed up until it contacted the fuel rail. The fuel rail was then
removed and diffuser depth was measured. The difference between the
measurements was between 0.110" and 0.145". The original
diffuser returned by the rebuilder has no apparent seal, the replacement has a
rubber seal molded into the top.
I took some measurements and drew up
the primary, fuel rail / injector /diffuser (see attached pdf.) It looks
like there are 2 differences between the diffusers that came on the 20B
and the replacements recently purchased. The height of the diffuser above
the seating surface is much lower on the replacements and the length of the
area that projects into the port/air stream is longer. The extra length
extending into the port is probably not an issue.
The shorter height of the
replacement seems like it will be a problem, the problem being a vacuum leak
around the injector. A secondary issue from a vacuum leak in this area
may be an effect on fuel droplet size. By looking at the injector, it
appears that a metered amount of air is intended to flow into the pintle cap,
presumably to aid in reducing the fuel droplet size. A vacuum leak in this
area may reduce the air flow through the pintle cap and the resulting
droplet size reduction.
I would speculate that at medium or
higher power levels the vacuum leak would probably have little noticeable
effect. I would expect that the most significant effect would be at or
near idle conditions. Since smooth idle seems to be difficult to attain
in many installations, it would certainly be prudent to try and eliminate this
issue (not to mention that it would be good practice to get it right.)
1. There seems to be a very
small gap (~0.010") between the fuel rail seating surface and the top of
the original diffuser. It looks like there should be a grommet that makes
up the difference and provides a positive seal. To anyone who has disassembled
a 20B, is there a grommet/seal the sits on top of the diffuser?
2. Same question as 1, for
anyone who has disassembled a 93-95 13B (13B-REW, I believe)?
3. Anyone have a source for
the proper 20B diffusers?
Any opinions and/or remedy
suggestions are appreciated.