2Cs - Misc > Webra Pipe

[Brian Young]

The 590 muffler gives up about 700 rpm to a tuned pipe
on same engine...sound about right? Ive also liked the
590 muffler, it produces a very good run.

Has anyone run the Webra pipe on the Webra 1.45 or
1.60? Im curious what lenght it would run best at.


--- David Lockhart <DaveL322 at comcast.net> wrote:
> Steve,
> 
> Agree with you 100% - well, with one exception <G>.
> 
> On a 2C, all exhaust systems are tuned to some
> extent in some RPM range - the good mufflers have so
> little tuning that it is not noticeable.  I've had
> very good success with the Bolly 590R on several
> 2Cs.  The power difference is substantial - to the
> point that I would say a muffled 2C is slightly down
> on power compared to a 140 DZ on 30%.  Personally,
> I'd still take the muffled 2C.  <G>.
> 
> Dave
>   ----- Original Message ----- 
>   From: Patternrules at aol.com 
>   To: discussion at nsrca.org 
>   Sent: Thursday, January 22, 2004 6:34 PM
>   Subject: Re: 2Cs - Misc
> 
> 
>    Dave a very good write up but I believe you
> missed one point, the way Jeff Hughes and me have
> been doing it, Muffler instead of pipe, no tuning,
> no midrange problems, no Idle problems, no EFI, no
> MC Carb, A little less peak RPM but plenty of power
> and for sure the simplest to setup. Extremely
> reliable and probably the best for anyone new to
> this sport.
>    Steve Maxwell
>   In a message dated 1/22/2004 2:36:45 PM US Eastern
> Standard Time, DaveL322 at comcast.net writes:
>     To add to several of the recent posts RE 2Cs,
> some misc thoughts/data from my experiences.
> 
>     The question has been asked, how much power is
> enough/needed - how much more is needed?  If you
> have enough power, and it is consistent, quiet,
> friendly, smooth, reliable, cheap, etc - you don't
> need more.  However, having too much power (haven't
> found it yet myself) allows several things - milder
> cams, smaller carbs, lower compression, richer
> needle setting, lower nitro, milder porting, milder
> tuned exhaust systems, etc - all of which are
> essentially trading "extra" power for something else
> that is nice to have - ie, cheaper, quieter,
> consistency, more linear response, more torque, etc.
> 
>     With 2Cs, I've posted before how the exhaust
> system can have a huge influence on not only the
> peak power of the engine, but also on the midrange
> running characteristics.  Tuning the exhaust for
> peak power usually has some nasty side effects -
> non-linear throttle and rich/lean spots in the
> mid-range being the biggest nasties.  The old
> "traditional approach" to mitigate the nasties was
> to test many combinations of props, plugs,
> compression, nitro, oil, pipe lengths, pipe designs,
> and port timing on the engine itself.  The point in
> time when the "average" pattern flier probably knew
> the most about the "traditional approach" was
> probably in the mid to late 1980s - piped 2C 60s
> were propped between 13,000 to 16,000 RPM on the
> ground (10-11.5" diameters and 7-9" pitches), and
> the tune length of the pipe (diverging/converging
> cone type, mufflers were rarely used) was 13-15"
> (plug to baffle).  After the introduction of
> turnaround and noise limits, and just prior to the
> 4Cs becoming dominant, 10,000-12,000 RPM (11-13"
> diameters, 9-12" pitches) and 17-20"
> (diverging/converging cone type, and baffle type,
> still no mufflers) were the norm for 2Cs.  A couple
> 2C guys on the fringe were running even bigger
> props, with longer pipes, and lower RPM.  My
> personal setup at that point (1992) was a Webra Race
> 61 LS w/ Dynamix using a CF pipe set at 22" and
> turning an APC 13-13N at about 9,500 - not a
> friendly setup - few aside from myself could set the
> needle, but the power was awesome, and whisper
> quiet.
> 
>     Today, the "traditional" approach to tuning a 2C
> still works, AND, some new approaches exist - the OS
> EFI system and the MC carb system.  The
> "traditional" approach today includes tuning the
> engine not only for peak power, but for peak power
> at a lower RPM and with linear throttle response as
> well - and relative to the mid/late 1980s, the
> average pattern flier knows substantially less about
> 2C tuning.  All three systems will yield the same
> amount of peak power - EFI and MC do not yield more
> top end power.  However, when the goal is peak power
> AND a smooth midrange - it is easier to achieve that
> goal using EFI or MC - the "traditional" approach
> requires substantial 2C knowledge and/or
> experimentation.  Very often the "traditional"
> approach sacrifices a little bit of peak power to
> get the smooth midrange (and retain some
> flexibility/consistency) and it is for that reason
> that the average EFI or MC setup produces a tiny bit
> more power than the std carb (traditional setup). 
> The "best" 2C setup, IMHO, is going to be one that
> is "traditionally" setup with the addition of EFI or
> MC, to allow very fine tuning and more consistency
> and flexibility (with regards to changing weather,
> props, fuel, etc).  A very poorly setup 2C is not
> going to become wonderful with the addition of EFI
> or MC.
> 
>     Aside - in my experience from running the OS140
> EFIs and 140 RX - the EFI system has a "sweet" spot
> - it wants to be propped between about 7,700 and
> 8,300 RPM on the ground which will yield about 8,300
> to 9,000 RPM in the air - if the 140 EFI is setup
> outside of that range, the power drops
> substantially.  OTOH, an OS140RX can be tuned to run
> extremely well from 7,400 up to 8,800.  I've not
> found a 2 plug head to provide more power or a lower
> idle - but the needle setting becomes less critical.
>  And while Shadel piston/sleeve is a great weight
> saver (40 grams), I've not found it to produce any
> more power.  And if the engine ever gets hot on the
> ground, the stock setup (ringed) idles a little
> better (never noticed a difference in the air tho).
> 
>     Regards,
> 
>     Dave Lockhart
> 
> 
> 
> 


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