----- 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)
|