Hi, Paul....I am very impressed with your contributions to such a
nice,
universal intake manifold.
Coupled with the injector holders and bell mouths, it resembles what
the
"professionals" such as
Mechanair and Powerspost are doing. Unfortunately, I just purchased
Dave Atkin's system (manifold
with throttlebody), but it appears that I might possibly use some
parts
of his system (like the
throttlebody) and still use your new system with the longer runners.
I
like the idea of moving the
throttlebody to the cold side of the engine. I don't know how
familiar
you are with Dave's
setup....any suggestions? Thanks again for making it easier to
obtain
a successful rotary
installation. Paul Conner, Mobile, AL
Got any pictures of what Dave provided? I think it is a race car
system and could be sold on ebay without much trouble.
Paul Lamar
Yes, Paul....here is a picture of the manifold, injectors and
throttlebody.
Paul Conner
That will work of course but it is probably tuned for something like
8500 RPM. Your power will be much less than it could be especially if
you have a 2.17:1 gear box which will limit your RPM to around 6000.
I am sure your airplane will fly on it however. My guess is 150 to
160 HP at 6000 RPM.
It appears to be a six port manifold. What has been done to the
engine porting?
It might not be so bad with a 2.85:1 box that would allow 7500 RPM.
Paul Lamar
Hi, Paul....actually it is a four port manifold. Nothing has been done
to the porting. I was just hoping I might be able to eliminate this
manifold, and go with the one you are working on, and somehow through an
adaptor or ? use this throttlebody? Thanks again. Paul Conner
Sure my manifold will work and that throttle body will work.
My guess is you will get about 175 to 185 at 6300 RPM depending
on the prop.
You will need to fab a sheet metal plenum on the other end
of the manifold. Make it strong as suddenly closing the throttle
will apply about 15 psi to the outside of the plenum.
Weld up a rectangular box just big enough to take the TB on
one end. My guess is about 7 x 3 x 10 inches out of .093 thick
6061 T6. You can rivet it up with angle and plate if you seal
it well. Here are shots of what Chuck Dunlap is using.
If you sell the TWM TB you can make it smaller 3 x 3 x 10
and use a simple butterfly as you don't need the TWM throttle
position sensor if you are using Tracy's EFI.
BTW Hi Chuck. It never occurred to me until recently and I did not
put two and two together until just now.
You are using a dynamic chamber hidden in the plenum correct?
If so I think your runners are twice as long as they should be.
IMHO a dynamic chamber doubles the effective runner length. I have
been real slow in realizing this. It has been festering in my
subconscious for the last four or five years. Mazda was never
very clear in their tech papers just exactly how the dynamic
chamber really worked and I think I finally have it figured out.
They are tuned at two RPM's. The fundamental length and double
the fundamental length. We don't need double the fundamental length.
That is for cars that need the torque down low. IMHO
the fundamental (short) length tuning is compromised for the
double length tuning.
The weird takeoff RPM characteristics of your engine gave me a bit
of a clue. Sad that I did not put all this together three or
four years ago. Won't take much work to convert it to a simple
plenum and tuned runners with your monster TB :-) Make sure
you have bell mouths on the ends of the runners as they are
worth 5% HP. IMHO you will gain HP at 6000 RPM.
Paul Lamar
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