Hello everyone. I'm new here and new to rotary engines. I hope that you guys won't think less of me because I don't own an RX7. I have a 1964 VW bug. I bought a totaled 1987 RX7 non turbo automatic (Hit very hard from behind) for a doner vehicle for my VW. Lots of people have but rotary engines in Vw's but no one I have been able to find can answer my question so here goes.
I understand that the second gen non turbo engines are 6 port engines. And I also understand that these ports (5th and 6th) are opened somehow by exhaust back pressure. Well if I put this engine on my VW, I won't be using the 3 catalytic converters originally equipped on the RX7 and would like to but a high flow muffler on it. How can I keep the functionality of the 6 ports extra ports without having to choke the engine to death? Thanks for any help you can give. Glad to be part of the group.

 

search electronic six ports or something like that, or electronic auxilary ports. basically you can use the factory smog pump with an RPM controlled solenoid valve (89+ cars have an OEM setup like this controlled by the ECU) or you can wire in a fully electric 12v pump. IMO the factory smog pump will be more reliable as you don't have as much electronics to worry about burning out and less wires.

http://www.idahorotary.com/6portsolution.htm

something like that.

 

Since you'll have neither backpressure from the cat, nor, I'm guessing, an air pump to tap, you'll need to set up an electric system:

http://www.rotaryresurrection.com/2n...elec6port.html

 

The 84-88 13B non turbo 13B motors use Exhaust velocity to actuate the aux (5th and 6th) ports.

It is a common misconception that it has anything to do with back pressure. Back pressure is bad in all motor vehicles, and even more so in a Rotary engine.

The mis-conception comes from people putting in the incorrect exhaust size for the vehicle. Many people put in a big exhaust from a Turbo (such as a 3 inch ID exhaust) or some lame "turbo" muffler from the local auto parts store and suddenly their aux ports stop operating.

This is caused by the exhaust gases escaping too slowly. The exhaust velocity has dropped too much. Too big of an exhaust is just as bad as too small of an exhaust when you are looking at exhaust velocity.

So, the properly sized exhaust for the engine will always result in better scavenging of the exhaust and properly working aux ports.

The other reason for the incorrect "back pressure" myth is that people often remove the main cat converter and do not hook up the feed line that is normally attached. The air feed for the main cat converter serves multiple purposes, one is feeding air to the 2nd stage of the monolithic cat, the other is too feed the aux ports. By just disconnecting the line, the aux port actuators no longer have any sort of feed. Of course the simple solution for this is to use a set up similar to the Racing Beat Power Pulse connector that has the feed for the aux ports already welded in.

Now the 89-91 non turbo 13B engines use the air pump as the feed for the aux ports through a switching solenoid. This method works as well as the motorized actuators found on the 03 and later non turbo 13B engines (Renisis series). The drawback to air pump actuation however is that the ports tend to slam open, as opposed to gradually/progressively open as found on the 84-88 and 03+ engines.

 

Thank you Icemark for that information. I was also under the impression that the exhaust back pressure actuated the valves. So what are my options? I currently have the entire RX7 to take parts from ,but will not be using any of the factory exhaust parts and would like to get rid of the smog pump as well. I will have to fab up my own exhaust system since there is so little room in the rear engine compartment of a bug. I am not looking for the thing to be any sort of rocket ship, but would like the engine to run as well as it does in the factory cars if not better (Without any internal modifications). I will search for some sort of electronic actuation device to actuate the ports, but if I understand you correctly, the electronics available on the market require me to retain my smog pump. Is this correct? Are there any options that do not require the use of the smog pump? I would prefer that the valves actuate smoothly as they do in the stock car rather then slam open. Thanks ahead of time for any assistance you may be able to give me.

 

You could also use a Racing Beat "Road Race" header that has a tuned air source for the actuators on the header.

 

The link I posted above assumes that you no longer have a smog pump - it uses a small electric pump:

Airpump 6PI Actuation

It's also possible to make an all-electronic solenoid-based system, depending on how much fabbing and tweaking you're willing and able to do:

Mazda RX-7: Electronic Aux and VDI Actuation

But honestly, as long as it will fit, I like Turbo II Rotor's answer best.