Webra 145 with Greve Pipe

[Jeff Hughes]

It's really related to RPM. A two stroke has both ports open so some  
the intake charge blows out the exhaust, the pipe sets up a pressure 
wave which packs this back into the cylinder. As you can visualize, 
with a fixed pipe length, this will only work at a specific rpm. So 
props with the same load will use similar pipe lengths. But any change 
that effects the RPM will require a pipe change. When I was running a 
pipe on my 1.40, I deliberately ran it an inch long so it would start 
to come on the pipe in the midrange, which softened the "peak". When I 
ran dirt bikes, we set them so they were very peaky, all's we cared 
about on them was HP.



> You will also notice a difference in results when you use different 
prop sizes. As a general rule you need to make the set-up longer if 
you use a bigger prop. (Assuming that you had it right in the first 
place.
> 
> Bigger can mean diameter or pitch. Some sizes interchange well, For 
example an APC 17 x 13 can swap with an APC 16 x14 with the same pipe 
settings.
> 
> Regards,
> 
> Eric.
> 
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of Lee Davis
> Sent: Wednesday, June 18, 2003 11:06 AM
> To: discussion at nsrca.org
> Subject: RE: Webra 145 with Greve Pipe
> 
> 
> The setup info I give on our web site is generic.  It works, but
> temperature, altitude and fuel type are a few of the variables that 
can have
> an effect.  Lengthening the pipe enhanced the mid-range in the 
particular
> case I mentioned, though I hesitate to make a blanket 
recommendation.  I've
> set up engines for many people.  I doubt any two ended up exactly 
alike.  As
> is the case for much of our equipment, manufacturer instructions 
will get
> you going, but they are not necessarily the last word.  It is in your
> interest to experiment and optimize.
> 
> Lee Davis
> Piedmont Models
> http://www.piedmontmodels.com
> 
> 
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of Keith Black
> Sent: Wednesday, June 18, 2003 1:39 AM
> To: discussion at nsrca.org
> Subject: Re: Webra 145 with Greve Pipe
> 
> 
> As long as we're talking about the Webra 1.45, RPMs and pipe length, 
what
> are some experiences with the Webra 1.45 and the Greve pipe. 
Piedmont's web
> site it recommends 27.5" to the first baffle, but recently Lee Davis 
posted
> that he has his set at 28.5" to the first baffle.
> 
> Mine's actually running pretty well at 27.5", I'm just wondering if 
I can
> improve it by moving it back an inch.
> 
> Lee, if you read this, why did you move yours out another inch over 
what
> your web site recommends? What did this improve (top end, mid range, 
etc.)?
> 
> Does anyone else have experiences to share with this combination?
> 
> Thanks,
> Keith Black
> 
> ----- Original Message -----
> From: "Jerry Budd" <jbudd at QNET.COM>
> To: <discussion at nsrca.org>
> Sent: Wednesday, June 18, 2003 12:00 AM
> Subject: Re: Webra 145
> 
> 
> > >Let's try again - what rpm are you guys getting with what props 
with the
> > >Webra 145?  I'm trying to tune mine with a Bolly pipe and have no 
idea
> what
> > >to look for.  I'm trying both a 17X10 and 17X12N prop.
> > >
> > >Thanks for any suggestions.
> >
> > 82-8300 rpm when new, 85-8600 rpm after ~30 flights.
> >
> > Magnum #1, OS-F or YS plug, ES-2C140L90 pipe set at 23-1/4" baffle 
to
> > plug, stock Mac's 2-1/4" rise header, and an APC 17x12 prop.  The
> > Webra MC (mixture control) carb I'm using gives a dead linear
> > throttle response with NO jump onto the pipe.  Setup this way the
> > motor throttles exactly the same as a DZ but with better 
performance.
> > With the stock ProMix carb it throttles a lot like the OS (rich in
> > the mid range).
> >
> > Jerry
> >
> > --
> > ___________
> > Jerry Budd
> > mailto:jbudd at qnet.com
> > =====================================
> > # To be removed from this list, send a message to
> > # discussion-request at nsrca.org
> > # and put leave discussion on the first line of the body.
> > #
> >
> 
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> 
> 

-- 
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