Webra 145 pump pressure ?

[RC Steve Sterling]

Sounds right on the nitro and oil then Paul. I think you are correct on the
pipe also. This is my first use of a pipe as well.  What I was surprised
with was how sensitive it was to pipe length.

When I first put my focus together, I got the measurement spot-on and it
worked well. As usual, I had the belly pan off and on for various reasons,
and one day headed for the field and it wouldn't run well. Blubbery in the
mid-range to the point it would flame out.

Changed plugs, messed with mixtures, ruined a whole day of practice. Took it
home, drove the neighbors nuts running it, trying to get the mixtures right
and all.

Had the thing on its back, ready to pull the pan and cowling to start
adjusting the pump, and noticed I had the coupling pushed up on the header
and pipe farther than before (stain marks). Measured the difference-- only
1/2 inch too long. Pushed them back to the old marks, cranked it up ....
like a different engine.

Other experts chime in here..... I'm no real expert.

Steve

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Paul Horan
Sent: Sunday, April 03, 2005 11:56 PM
To: discussion at nsrca.org
Subject: Re: Webra 145 pump pressure ?


Steve,
    The 20 and 5% I am refering to is nitro.  I mixed 2 gallons one 5% nitro
with castor/synthetic oil and one 15% nitro with all
synthetic oil to get 10 % nitro with the oil being composed of 2/3 synthetic
and 1/3 castor.  I want the castor to guard against
wear during break-in.  I am new to tuned pipes, the pipe is long to keep the
rpm down during break-in.
    If I understand you correctly, when I shorten the pipe it will richen
the mid-range.  Is this correct ?   Currently I am
delibrately rich at the top end and the mid-range is only slightly rich
(pinch test).
    I am reluctant to mess with the pump and hoping that as I get more fuel
through the engine the mid-range will richen up.  Is
that reasonable ?

Thanks,
Paul

----- Original Message -----
From: "RC Steve Sterling" <rcsteve at tcrcm.org>
To: <discussion at nsrca.org>
Sent: Sunday, April 03, 2005 5:13 PM
Subject: RE: Webra 145 pump pressure ?


> If I am reading your message correct, you are running 25% total oil (20%
> synthenic and 5% castor)??
>
> If so, that is probably too much oil for the Webra. I once tried 20% total
> oil, and it didn't like it much. I backed down to 17-18% total oil and it
> ran much better. I happen to run all synthetic now, but have tried some
with
> a little castor (total oil 18%) and it ran fine on that also.
>
> 7300 RPM is pretty low on a 16.5 x 12 prop for this engine. I think most
get
> more like 7900 RPM. You may need to adjust pipe length a little. If it is
> anything like my Greve pipe, it really makes a big difference on the
> midrange mixture as well. My troubles were with too rich midrange. I'd try
> different fuel, then try a 1/2 inch pipelength change first before trying
> pump pressure.
>
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of Paul Horan
> Sent: Sunday, April 03, 2005 10:09 AM
> To: discussion at nsrca.org
> Subject: Webra 145 pump pressure ?
>
>
>    My Webra has a good top and bottom end. Only about a gallon and a half
> through it so far.
> The top end is nice and smokey, idle is solid, but the mid range is very
> little smoke.
> It is on a Prophecy running a 16.5 x 12 at 7300 rpm with the Macs pipe at
27
> inches.
> Most of my flight is at roughly 1/2 throttle.  When I land the oil residue
> on the coupler and
> fuselage is medium brown - fuel is a mix of 20 % synthetic and 5 % castor
> synthetic.
> Main needle is open 1.5 turns.
>    I am wondering if I should increase the pump pressure to richen up the
> midrange.
> Or am I just being too fussy ?
> Thanks,
> Paul Horan
> KC5NF
> AMA 57131
> NSRCA 3606
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