OS 91FX matched to Mac header and 15cc pipe (aircraft/standard)

[Tony Stillman]

Don:

I would just suggest that you use a 91 size tuned pipe (15cc) and leave the
pipe and header full length as they come out of the package.  You could tune
it down the road, but you probably won't really need to....

Tony Stillman
Radio South
3702 N. Pace Blvd.
Pensacola, FL 32505
1-800-962-7802
www.radiosouthrc.com
----- Original Message ----- 
From: <DPeckNSRCA at aol.com>
To: <discussion at nsrca.org>
Sent: Friday, October 17, 2003 12:11 PM
Subject: OS 91FX matched to Mac header and 15cc pipe (aircraft/standard)


> Hi Guys,
>     Our club sec. is refurbishing his dad's EU-1 and has anew OS .91 FX 2
> stroke.  Drew wants to know what header/pipe length settings to use.  My
limited
> Rossi, Picco .60 drawings used measurements from exhaust port to pipe high
> point.  Props then became the flying and "pipe tuning length" factor, to
get the
> engine "on the pipe."
>     The MAC Co. is not giving any info. as they "haven't any data."  I
told
> Drew maybe he bought the wrong brand.  Seriously, my man Drew is our
club's VP
> for 2004 and may very well be our tenth local entry in our Huntsville, AL
RCRC
> 2004 Sept. Pattern Meet.  I don't want to mislead him with poor info.  All
my
> attention has been .91YS 4S using 13.5x10 or 14x10 APC.  I am asking for
the
> following advise:
>
> 1. Prop size (with muffler) to test fly EU-1 (big 60 size wing CI,
1,200+?)
> 2. Recommended starting prop size with header/pipe
> 3. Suggest minimum and maximum pipe length, measuring exaust port to high
> point of pipe.
> 4. Any RPM specs. you may have on idle and top end of OS .91 2S motor.
> 5. Comments wanted on use of .91 2S using back pressure from pipe/header
to
> pressurize tank.  I have Rossi old pipes with Mac pressure fittings for
back
> pressure.  If you do recommend tank back pressure, where do you drill your
> pressure fitting? At approximately what point on pipe, or header,
(distance for
> exaust port)?  Some guys ran pressure fitting just in front of the pipe
high
> point.  That sure made a long line, however, ducted fan 91's live with the
> pressure!  Seems like our lower RPM's of today are not worth the pipe
pressure
> fitting trouble.
>
> Thanks for your reading time.
>
> The 2nd best "billfold builder" in the Rocket City,
> Don Peck
> NSRCA 585
>
>
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