flyrotary@lancaironline.net Mailing List Archive

On 2/23/2017 4:26 PM, durabol35@yahoo.com wrote:

Dear FlyRotary Group

My name is Brock and I've recently joined this group. I am working on a original design Rotary Powered WIG (Wing In Ground-Effect) vehicle that flies in the cushion of air between then wing and water. Eventually I would like to build a plane (LSA like) I can take up in the air but for now want to focus on this. I'm still in the research phase (for the last 15 years!) but hope to start building shortly. I'm presently reading through RWS literature: Magazine articles, the Aviator's Guide to Mazda Rotary Conversion and the Mazda Papers and have learned a bunch.

I've recently obtain a running 1986 RX-7 13B rotary engine. For simplicity I'm considering converting to carbs and aftermarket ignition since I'm worried about getting the wiring sorted out for the stock ECU since it seems complicated and RWS says it is not suitable for airplane use. I've gotten the impression that a properly adjusted carbs will perform similar to EFI (that doesn't use direct injection) for spinning a propeller and RWS reports only 10% worse mileage. I had a look at the RWS website but didn't see the ignition system that uses the stock crank angle indicator and coils so I'm wondering if it is still available or a suitable replacement?

I was planning to use separate carbs and fuel pumps for each rotor for redundancy so I can shut down one rotor and limp home in an emergency like an ignition or fuel system failure. I know this type of redundancy increases the number of parts that could potentially fail but it still seems like a good idea to me. The engine has a 6 port intake with the two center ports feeding both rotors while the outer ports each feed one rotor. I was planning to seal the 2 center ports and just use the outer ports but that was before I read that they are "boost" port and close much later than the center ports. Like the name suggests I assume that the boost ports are for high power output but I'm worried about fuel efficiency just using the boost ports. I've read in the "Aviator's Guide to Mazda Rotary Conversion" the author used a 3 carb setup and 2 fuel pump and in normal operation all three carbs are used and for an emergency the engine can run on either the outer two carbs or the center carb. Based on this example the center ports should be used but the engine does run (in an emergency) on just the outer boost ports. I suspect the center ports are important or Mazda wouldn't have made the engine that way, but perhaps just for low power levels or emissions?

Brock

Hi Brock,

Lots of ground to cover. I suspect that Tracy would not recommend the original 3 carb setup he used, if you want decent power from the engine. You can't tune the intake, since the center carb is siamesed to both rotors. The rotary is pretty sensitive to intake tuning, and the older 13B (pre-Renesis) is also very sensitive to exhaust tuning.

A Microsquirt would work for full engine control, or a Megajolt would work for just ignition. The Megajolt would require changing the trigger wheel to a 36-1 Ford EDIS style trigger wheel. Len Hanover has also published to this list a method that has fixed advance using just 2 crank angle sensors and a single trigger tab on the flywheel.

I don't know of anyone that's set up a rotary with separate controllers for each rotor. Problem is that the vibration level is pretty extreme if you shut down one rotor completely. It's not that difficult to set up redundant ignitions that each fire both rotors, and if you stick with a carb (an unlikely in-flight failure point, once dialed in), both rotors will get fuel.

What we really need is for Tracy to come out of retirement & write a revised conversion guide using the Renesis and modern controllers.

Charlie
(Ducking & covering....)

:-)