it does anyone have a 13b with a micro tech ignition sys i have one
and i have tried just about everything i can think of but iam still
only getting 5000 rpm and only if i advance the timing if i take the
prop off of course it will wind up to 9000 in a hurry the spark is
good to both rotors ive moved the timing in both directions only to
vary the rpm from 3000 to 5000 my a/f ratio i s from 12 to 13.5 down
around 10 at idle i am not sure if its the computer or the engine any
ideas
bob obrian
What is the gear box ratio?
What is the prop diameter?
what kind of porting?
Paul Lamar
Rd 1c 2.85:1
74 dia 88 pitch
standard 6 port was it so close i couldn't see it
thanks
bob OBrian
Mostly the prop is too large. Cut it down to 68" in dia. A p-port
would gain 50 HP at least depending on what your 6 port manifold
looks like. Send me a picture. I can then estimate the power.
Paul Lamar
I'm having the same problem with my naturally aspirated six port RX8
rotary in my Bush Caddy aircraft, max RPM is only 6100. I'm using a
three blade 76" magnum Ivo prop. I removed one blade and tried it
with the two blade set-up, problem even got worse, down to 5600 RPM.
Doesn't make sense to me. Another thought I have is an exhaust
restriction. I'm using a racing SPINTECH 2 1//2" inlet & outlet
muffler. Anyone have any thoughts on this?
Thanks, Bob Forbes
What is your gear box ratio Bob?
It is not the number of blades. The diameter is too large. The tips
of the prop are running into the transonic brick wall. Cut it down to
68" and sand the tip to a thin air foil section.
Here is the best muffler to use. Sounds better as well. Works
somewhat like a ramjet.
That SPINTECH will destroy it self. Inspect it internally with a
Harbor Freight digital inspection camera after every flight. Aircraft
have crashed when an automotive muffler was used and plugged up. VERY
IMPORTANT!
The coax muffler is much easier to inspect.
The intake manifold is critical. Here are some old pictures of your
manifold. We had this discussion in the past and I am sure I
recommended longer intake runners. There should be plenty of room in
a Bush Caddy for longer runners. 18 to 20 inches is about right.
Paul Lamar
Thanks for your resourceful response Paul. I'm using Tracy's 2.85:1
PSRU. I will cut the prop down and try that when I get time. Yes,
we have had this discussion pertaining to my intake manifold in the
past. I know my intake would be much better with longer runners, I'm
just reluctant to spend the time re-doing my intake system. If I can
get 200 HP with the way it is I won't need to worry about, if not
I'll have no choice but to change it. My Bush Caddy requires 180 -
250 HP. Today's engine run, rpm maxed out at 5800 and 114 hp.
(according to Tracy's engine monitor) Not good!
The SPINTECH muffler is completely constructed 321 SS, with a very
simple welded-in baffle system. Thanks, I will keep an eye on it
with a inspection scope.
Paul, did you get your ignition system up and running, and is it on
the market yet, it has to be simpler than Tracy's to set-up. There
must be a simpler system then Tracy's out there somewhere. I'm about
ready to send Tracy's EC3 to the bottom of the river. Too many
adjustments and mind boggling to set up. I have it running well at
mid-high rpm's, but runs lousy at low rpm's. If there are other
folks on your news letter list having difficulties with Tracy's
engine controller would they please let me know. I'm at a lost with
this one.
Thanks again, Bob Forbes
You will need the proper length to get 200 HP assuming there is a
good match between the runners and the ports. 200 at 7000 is
certainly doable.
What diameter are the runners? It is tricky matching round tubes to
oval ports. That is a major reason I gave up on side ports as I would
have had to make the casting patterns over and over again every time
Mazda changed the shape of the ports. The round hole of a p-port in a
rotor housing was and is much simpler not to mention an easy 250 HP.
The static RPM should go up to about 6900 cutting down the prop to
68" The IVO is not the best choice in the world as it is variable
twist rather than variable pitch. Sanding the tips down should help a
little bit. The RPM will go up when you are in the air as the prop is
stalled when running it up static tied down. The prop usually comes
out of stall around 60 MPH.
However there must be something else going on when you went to 2
blades instead of three.
My latest iteration on the ignition system is simpler. There for a
while one had to have one of my fast low cost computers to control
it. I built in a little more circuitry in to allow the use of a
simple trigger disk on the nose of the e-shaft. This takes the place
of the computer for spark programming. The number of holes and their
spacing can be changed to control the number of sparks and how many
degrees after top dead centre they occur. It can still be triggered
by a computer but there are lower demands on the software and the
speed of the computer.
A super simple to program Maximite will now do the job along with
EFI and EFIS.
This is what the latest packaging looks like. The trigger disk is
rotated here by an DC electric motor for demo and testing purposes.
The rotary powered RV4 I am going to test the ignition on now has a 2
barrel 500 CFM Holly carb. I got rid of my Tracy stuff for the same
reason you did :) Unfortunatly the gear box is 2.13 so I need a new
gear box and a prop that rotates in the right direction.
Paul Lamar
Paul, You asked the diameter of my runners. I used half of the
stock intake as the attached photos show. Notice the bevel (bell
mouth) in one of the photos. I thought this would be the easiest
transition from oval to round.
Bob Forbes
Good illustration of why we went to P-ports :-) Too complicated to
deal with six ports. Intakes are aerodynamic systems and skin
friction drag matters. Six small runners have more skin friction drag
than two large runners. Mazda had no choice in the matter as they had
to get torque and HP at 3000 RPM so the car would accelerate in 6th
gear on the free-way. They should have installed an automatic manual
transmission instead and they would have wound up with more maximum
HP and a less bulky intake system. As it is now in the RX8 the
intake takes as much room as the engine. If they were cleaver they
would have copied the rotating variable length intake runner system
from Mercedes and others.
Be all that as it may one needs to deal with it or take ones engine
apart to P-port it. That would be the fastest in terms of time. The
cost would be about the same. Here is what Milo Burrows came up with
to get the required runner length. Nice job Milo.
Don't be afraid to take your RX8 engine apart. It is just a storage
problem to make sure the seals go back in the same slots they came
out of. Other than that it is 10 times easier than a piston engine.
It comes apart in a half hour. Cleaning the rotors takes the most
time but I get them bead blasted for a couple of bucks each. Make
sure you protect the rotor bearings.
There are plenty of how to do it manuals out there for free.
Paul Lamar
What kind of muffler is Milo running that won't work (?)
bruce buksyk
What do you mean? Be direct.
Paul Lamar
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