Hi Duncan and Gilles Thank you for information you provided. For the past
several
days we have been evaluating the flow characteristics of Rotax CAB on our 914.
We did not remove the engine from the mounting ring to install the CAB but
made slits to go over ring. Perhaps that caused a little leaking, but don't
think
too much. We used a shop vac with an airspeed of 35mph and a leaf blower
with airspeeds of 50mph, 75mph and 100mph. First test was not too impressive.
We purchase the CAB from Lockwood, looked like it was run at the factory for an
hour. #1 cylinder where the baffle touched the fins was pretty brown indicating
high heat. #2 cylinder was somewhat showing brown. Flow was almost nonexistent
on #1 and only a little on #2. Aft of #4 wasn't too bad and #3 aft was very
bad, a little more than #2. Between cylinders was dismal. There was a ton of
air exiting aft of cylinders mostly on the stbd side where Rotax kinda has an
exit to blow some air on ignitions, but it was grossly overdone. We now have
flow where 35mph is giving us at least as much on cylinder #3 and 4 as 75mph
was on stock configuration, even more air between cylinders and #1 and #2 is
getting
same as 100mph stock configuration. In process of glassing cutout for alternator
and install of baffle and scoop. Stock configuration with 100mph and
the CAB just sits there. With modified CAB even at 35mph it lifts in back! We
will be installing 1 bolt ontop the center of case to hold it in position. If
engine was removed from ring, the ring may have held the CAB down? Will post
pics when complete. If I'm going to take a drag hit adding a third air scoop on
the snout, might as well make it count. Net is we now have good airflow to #4,
a little more airflow to #3 than #4, really good airflow between cylinders,
perhaps a tiny bit more on starboard side (turbo side), and lesser airflow to
front cylinders compared to #3 and #4, but way better than stock configuration.
Because we have 2 eyeballs that's blowing air on front cylinders, We're OK
having a l!
ittle le
ss airflow from CAB on front cylinders and we are going to cut off 3/4" of the
CAB to allow some of the eyeball air to better hit fins. Stay tuned. Ron P.
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http://forums.matronics.com/viewtopic.php?p=503628#503628
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