[NSRCA-discussion] OS 120AX header?

[J N Hiller]

16 x 10 should be no problem. I have run one all season with stock muffler.
I didn't like how many RPM's the 16 x 8 turned in horizontal flight.
This may be a little off subject but may be of interest to other 120AX
users.
I fought a rich midrange (poor transition) from day one in order to keep
from running too lean on a long vertical pull, which seamed to get worse in
cool air. I have two motors that have different carburetors and focused on
this as a problem even though both acted similar eventually concluding that
there wasn't enough muffler pressure. I have never gotten along well with
pumps so I tried restricting the muffler outlet using a short exhaust tube
(3/8" ID) with a brass tube insert. I tried a couple different sizes
settling on 13/32 OD, which is pinched on the end from cutting with a tubing
cutter (.350" ID). Flaring the other end keeps it in the exhaust tube
without clamps. I also tried an OS-"F" plug which I thing may be better than
the #8. It will be 9 months before I can run it in hot weather but I was
able to run leaner without starving in the verticals and the transition is
immediate.
Jim Hiller
Spokane

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Ed Alt
Sent: Saturday, October 06, 2007 5:44 AM
To: 'NSRCA Mailing List'
Subject: Re: [NSRCA-discussion] OS 120AX header?

Sorry about the loss of your plane Jon.  I can post results with different
props when I get things together next weekend.  The combo will be the 120AX,
a KM wrap header, a medium ES pipe. I'm looking to see if this will handle a
16x10, which I suspect it will.

Ed

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
JonLowe at aol.com
Sent: Saturday, October 06, 2007 7:33 AM
To: nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] OS 120AX header?

In a message dated 10/3/2007 10:22:13 AM Central Daylight Time,
jnhiller at earthlink.net writes:
Jon, I will be building a new airplane this winter and I am considering
using a pipe. I want it to be masters capable and a little more power won't
hurt. What pipe are you using? Are you using a pump? What size prop?
Thanks
Jim Hiller
I'm using a Macs 1092 Quiet pipe, Perry pump, and a 16x8 prop.  Was still
experimenting with the prop and pipe length when I lost the plane.

Jon Lowe

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