Ed,
Thanks for the explanation.  Now i know why they are separated.  Looking at the ports I was wondering if an oval tube shape for the runners would be appropriate.  I don't think that it is available, however.

Joe
----- Original Message -----
From: Ed Anderson
To: Rotary motors in aircraft
Sent: Thursday, July 27, 2006 10:02 PM
Subject: [FlyRotary] Re: Intake design 101

Hi Joe,

Each chamber has a secondary and a primary port (six ports have an auxiliary port which is like an additional secondary port).  Even thought a chamber has a primary and secondary, the primary and secondary for a port  normally have different intake timing.  Additionally, the opening of the intake port generally generates a very strong pulse (residue exhaust gas bursting out of the intake when it opens).   Since the intake and secondary port of each rotor are 60 deg out of phase timing wise with the other rotor, the pulse generated by each port can interfere or assist with intake airflow (depending on rpm, manifold air temp, density, etc).

I personally prefer to keep the intake ports separate to preclude interference.  Having said that - I have successfully flow with a system that combined the secondary intakes and primary intakes, so what you propose can be done. However, after trying six different intake configurations,  I have found though that I get the best performance (for our rpm) with 4 separate tubes feeding the throttle body.  Keeping in mind I have a "Plugs Up" installation which generally gives me a bit more room in running intake tubes.   Other arrangements have been tired and certainly work, so this is no magic formula - just  based on my personal experience.

Yes, the tuning (length) of the tubes should be determined by the rpm band that you want the most airflow enhancement.  It appears that a tube length from block to Throttle body between 17 and 21" generally gives good results.  Also, avoid excessive large tubes  diameters as intake air velocity is important in stuffing the chambers and larger tubes results in  less velocity.  I found that 1.25" dia tubes for the primary and 1.5" dia tubes for the secondary works well.

I originally had my intakes merged into a two runner Weber style manifold.  A two port Weber style throttle body with two 2" dia intakes.  While this was the cats' meow for a racer turning 9000+ rpm, it turned out to be disappointing  in aircraft use with lower 5000-6000 rpm.   When I replace this "racers'" set up with 4 smaller dia tubes my ROC increased by 300 fpm immediately.   Unfortunately my original fuel injection system died and I  did not get to collect further data on my old six port 1986 engine before deciding to switch to a 91 turbo block.

Hope this helps.

Ed

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW

1----- Original Message -----
From: Joe Berki
To: Rotary motors in aircraft
Sent: Thursday, July 27, 2006 9:24 PM
Subject: [FlyRotary] Intake design 101

I am using a 89 block for mock up and maybe rebuild.  Looking at the intake ports, there are two ports at the front and rear of the block then there are two rectangular ports in the center housing close to each other.  Others have fabricated intakes using 4 tubes. I assume it is OK for the two outboard front and rear of block to be fed by one tube while the center two ports need to be fed individually. Is this correct?  The length of the tubes is determined by where on the rpm vs Hp band you want to operate at? Thanks

Joe Berki
Limo EZ


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