----- Original Message -----
Sent: Saturday, February
07, 2009 7:33 AM
Subject: [FlyRotary] Re:
renesis intake possibility
Hi Bryan,
Welcome. Here is my experience using
a TWM throttle body (a different model than you are looking at). Back in
1992 there was no one around that I was aware that could provide any answers to
what made a good induction configuration for a flying rotary. So I turned
to the only “rotary aware” crowd around and that was those racing
with rotary engines.
So after discussing my needs, I purchase a
TWM throttle body with 4 injector positions. It was a two throat (Webber
style) design with each throat 2” in diameter. Two injectors per
port (I used MSD 32 lb/hr injectors that fit the injector holes) for a total of
4 injectors on the TB. The TWM throttle body was then bolted to a cast
aluminum “Webber” style rotary intake manifold which then took
the two TB channels and divided them into 4 (two primary and two secondary)
distribution runners.
I estimate that the best HP I ever made
with that set up was around 130-140HP. My static rpm was 4800 swinging a
68x72 two bladed wooden prop using the 2.17:1 gear ratio.
I later replaced that arrangement with 4
tubes of smaller diameter (1 ¼” for primary and 1 ½” for
secondary), made the runners longer in length and install the stock Mazda 3
port TB which had considerably smaller openings than the TWM arrangement.
I immediately picked up over 300 fpm
increase in my ROC and top speed moved from 186 MPH TAS to 195 MPH TAS.
As I learned over the years, it became
apparent that what works great for the racers turning 9000 + rpm may well suck
(but may not suck very well – pun intended) at 5000-6000 and was
therefore of questionable use for aircraft. As best I could figure out
the problem, it appears that with the large runner openings and runners that
the mixture velocity in the runners was very much lower than optimum.
That meant the air mass had little momentum and did a poor job of filling the
combustion chambers during the short time they were open. By going to
smaller runners, the mixture velocity increased considerably and resulted in
more mixture in the combustion chamber and more power. Now if I
could of somehow (using a shifting gear box?) have gotten my rpm range up into
the 8000 + range, then that intake system might have been the cat’s meow
– but, of course, I could never get above 4800 rpm static (and about 5400
once airborne)
Now the TWM Throttle body in the photo
based on your description may not have the same problems as it does have a
considerably smaller throat than the one I used. I personally do not
believe the use of the four throats would give you what you are looking for
– however, the use of two of the throats (one module) might work.
You could always place your second injectors else where on the secondary part
of the intake.
Just my opinion, of course, if the price
is really good, you have little to lose if it doesn’t work out.
I now use a $25 65 mm dia Mustang throttle
body which is much lighter (and much, much cheaper) than the TWM model I
purchased back over 15 years ago.
Good luck on your project
Ed
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Bryan Winberry
Sent: Saturday, February 07, 2009
8:57 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] renesis
intake possibility
I have a chance to purchase a TWM throttle body(see
attch pic) at a very low price. I have a couple questions for
the group.
The inlets are 42mm (appx 1.65 in.).
Is this too big to the point that they would be incompatible with the
injectors? I plan on using 1-1/8 and1-1/4 in runners.
Also, the bosses are sized for Bosch,
Rochestor, or Lucas injectors. Does this necessarily eliminate my using
the stock Renesis injectors?
This setup also would allow the use of a lightweight
airbox thus simplifying the intake system from a manufacturing
standpoint.
RV7, Renesis,RD-1C,EC3,EM3 (in the pipeline I
hear)
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