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Date: Sat, 21 Aug 2004 13:54:21 -0400
From: Mike Robert <pmrobert@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: EM-2 MAP readings
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Barnhart wrote:

> Rusty,
>  
> Also going with a TWM  TB, the model 3003.  Setting it up for one 
> injector per rotor.  Going with 72 lb injectors and 57 mm bores.  Not 
> flying yet. Hope this may help. Will try to bring it down to Tracy's 
> in October.
>  
> Barny
> MGDQ 20bt
>
>     ----- Original Message -----
>     *From:* Russell Duffy <mailto:13brv3@bellsouth.net>
>     *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
>     *Sent:* Friday, August 20, 2004 7:14 PM
>     *Subject:* [FlyRotary] Re: EM-2 MAP readings
>
>      
>     Thanks for the comments Mike.  I agree, and think it would be
>     difficult for the TB ports to read accurately at high velocity. 
>     That being said...
>      
>     I just hung up with TWM, and they believe those ports are
>     completely accurate in their TB.  He asked what size TB I
>     had, what engine, and about what HP I thought it was capable of. 
>     After hearing all that, he said my 42 mm bores were simply too
>     small, and that I'd need at least 45's.  When I pointed out that
>     my runners were only about 42 mm, he basically said "start over"
>     :-)   He did mention the possibility of adding a crossover tube
>     between the two runners, to allow one to steal from the other, but
>     I probably wouldn't do that unless I was committed to building
>     another intake if it didn't work.
>
Hmm, Weber was pretty much upfront with the fact that their TB ports 
were only for balancing idle and shouldn't be relied upon for accurate 
readings at any sort of power setting. Perhaps the TWM port  is placed 
differently than the Weber TB. IMHO, I think your 42s should do just 
fine at the revs you're turning. In fact, I think the intake charge 
velocity created by the 42mm tract may help you. I have info here (not 
in the attic!) reference intake VNE as well as a link to a calculator 
for gas velocity in a pipe. The link is 
http://not2fast.com/gasflow/velocity.shtml - you'll have to do the 
metric/English conversion thing but the math is sound. I'll post the gas 
velocity  thing later when I can get to the info. I want to say 600 f/s 
but will confirm.

>      
>     BTW, he guessed right off the bat that it was on an airplane, and
>     he mentioned that he really wished we wouldn't put their TB's on
>     airplanes, because it made him nervous.  I assured him that I
>     wouldn't sue him, and that his TB was higher quality than anything
>     I could cobble together, so he was actually increasing my chances
>     of survival :-)  
>      
>     At the moment, I've decided that I just don't know what's going on
>     yet :-)  My only benchmark is Tracy's 6200 RPM at 120-130 mph in
>     climb, so I'll see how I compare to that this weekend (weather
>     permitting).  I'm also convinced that the engine is producing more
>     power than before, due to the rapid rise in temps now, so I'll
>     also take a look at climb rate, and top speed at whatever altitude
>     I can get to with the clouds.  Heck, maybe I'm worrying about
>     nothing.
>
The real world is the ultimate determinant. Amen!

>      
>     Maybe Ed will hurry up and get his conversion done so we can get
>     some more data.  He's probably lapping his input shaft now (which
>     sounds a little nastier than intended) :-)
>

!

>      
>     Cheers,
>     Rusty (maybe an ankle weight on my right leg) 
>      
>      
>
>
>
>      
>     ------------------------------------------------------------------------
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>

    -Mike