Webra 145 with Greve Pipe

[Bill Carpenter]

Thanks for reply,

I just came in from doing some pipe tuning and found that, if I peak the
pipe, the engine won't come on the pipe from idle unless I pinch the fuel
line momentarily, then it "jumps" on the pipe and holds the rpm.  If I
richen it up a little the problem gets worse, to the point that the engine
will die from loading up if I don't pinch the line.  Lengthening the pipe
reduces the rpm but also softens the jumping effect.  I guess this is what
the MC carb is all about with the Webra 145??????

I think I'll take your advice and run the pipe longer.

----------
>From: "Jeff Hughes" <jhughes at hsonline.net>
>To: discussion at nsrca.org, <discussion at nsrca.org>
>Subject: RE: Webra 145 with Greve Pipe
>Date: Wed, Jun 18, 2003, 11:06 AM
>

> 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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