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Dennis,
Yes, it used a dynamic chamber to direct the pulses from opposing rotors into each other, hopefully at the right time. I currently use an open plenum on the Renesis with short 13.5" (but very clean) runners. I'll never know what the old manifold was really tuned for without a good dyno run but it was better at takeoff & climb (about 6200 - 6300 rpm) than my current manifold. New one can only manage 5800 - 6000 at takeoff At 7200 - 7400 the new one takes the lead. You can actually feel the engine get stronger as it accelerates through 7200. Unfortunately, there are almost no occasions to actually use the engine in that range with a fixed pitch prop. It sure would be a rocket on takeoff if I had a variable pitch prop though.
ROC on old manifold was 2650 fpm, solo, 12 gal fuel on board, standard day conditions. New one can only manage 2300.
Just finished plumbing the fuel system in the RV-8 with only a few fairings and position lights left to install before first flight. Hoping for about 4000 fpm ROC.
Tracy Crook
On Fri, Jan 2, 2009 at 11:46 PM, Dennis Haverlah <clouduster@austin.rr.com> wrote:
Tracy:
Could you give me a little more detail on the manifold you used that gave the best performance. (1). Was it designed so that a pulse exiting rotor #1's runner would flow into the open end of rotor #2's runner or did it use a large plenum similar to what you have on the Renesis in the RV-4. and (2) Was the manifold good for takeoff power vs high speed power or overall good at both.
Thanks,
Dennis H.
Tracy Crook wrote:
Yep, you're right Dennis. I had mentally reversed the order of the manifold valves and my measurements were between the face of the block and entry to the dynamic chamber instead of port opening to center of chamber.
My best overall manifold that I used on my 2nd gen engine measured about 20 inches using your points of reference. Also keep in mind that the 4 port Renesis was tuned for a power peak of about 7400, not 8500 like the 6 port version.
Tracy Crook
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