Webra 145 pump pressure ?

[Paul Horan]

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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