Should be an interesting experiment Paul,  can't wait to hear results.

 

 I tried a very short and now a medium-short manifold and find that it works well IF it is very "clean" (proper diameter runners, no change in cross sectional area, well matched to ports, etc, etc)  The very short runners gave up some power at climb rpm (FP prop) but did OK at cruise & top end.  The Medium-short version works about as well as my long (so-so clean) manifold (~17" runners)  and real good at top end.

 

FWIW, my guess about your dripping throttle body is condensation on the runners & throttle body walls.  Gravity does the rest.  Agravating the problem is the "cool side injectors".  Someone called this arrangement the "Holy Grail" of intake design.   I'd call it the "Sacred Cow".

 

Tracy   ( eat sacred cow for lunch).

----- Original Message -----

From: Paul

Subject: [FlyRotary] Re: Short intake manifolds

Hi, Tom....I saved a few posts that addressed the problem you were referring
to. The folks at Mistral also went into a lot of detail about it. Problem
is, they were talking about the LONG intake runners, and having the
injectors at the far end, away from the engine. Power pulses problems,
incorrect fuel mixtures, etc.
     I am not going to try the short manifold, (since I received one with
the bolt-on fuel/ignition package that I purchased from Atkins Rotary), and
see how it works. I understand Dave Atkins has been using his for quite some
time, with a lot of cross-country trips under his belt.
    Also, hearing Al's comments helps as well.  What the heck....I built an
experimental, so I guess it's expected I have the need to experiment a
little. Thanks for the input, Tom.  Paul Conner

----- Original Message -----
From: "Tom" <tomtugan@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, December 14, 2004 11:36 PM
Subject: [FlyRotary] Re: Short intake manifolds


> Paul,
> There was a discussion here a few weeks ago regarding 'back pulses' in the
> intake manifold.  Sorry, that may not be the correct term.   IIRC, seems a
> short manifold  may have issues, one being fuel droplets being expelled
> the
> opposite direction.   Let me suggest the potential for it to pool in your
> 'outer chamber' and another potential for a backfire to ignite it.
> Hopefully
> that is blatantly wrong so those who know will step in and straighten it
> out.
> You can tell by my terminology that I don't talk motors much.  Also, seems
> I
> read many years ago that the one reason aircraft carburetors are hung
> below the
> motor is so any fuel remnants would fall out and evaporate and not pool,
> lessening chances that a backfire would have something to ignite.  This,
> just
> idle chat.
>
> Tom
>
>
> --- Paul <sqpilot@bellsouth.net> wrote:
>>  My question is....With the
>> short manifold putting the TWM throttlebody over the top of the exhaust,
>> has
>> Dave had any problems with fuel dripping out of the throttlebody after
>> engine shutdown?  Also, did he put any kind of heat barrier between the
>> exhaust manifold and the throttlebody?
>
>
>
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