I'm just wondering if someone can give me the down low on all this 5th and 6th ports business. I always hear about them opening, and the 3800rpm problem and whatnot. Just don't know what is happenind exactly. Is it like there are 4 ports open always and then 2 extra at higher backpressure? Are they one intake and one exhuast or what?

Thanks!

 

Ok, here you go- In this message I will refer to the 5th and 6th ports as "Secondary".
The seconday system is actually 2 seperate systems, the seconday fuel injectors, and the secondary intake ports.

1-Fuel system: Basically, when the engine gets over about 3800 rpms, the seconday injectors come online to supplement the primary injectors, and to spray fuel down the ports that open at 3800 RPMS. (next)

2-at 3800 rpms, the secondary intake ports open up. This larger volume allows the air to move more freely into the engine, improving power just like opening up the exhaust system. (Try breathing through a straw, you might do while sitting still, but try it while running!)
You're probably thinking, "OK, well why don't leave the ports open all the time?" Well, at lower rpms, if there is smaller volume in the intake, the air will flow into the engine faster, giving a "ram" effect to the air-fuel mixture. This gives much better low end torque.

The 3800 hesitation happens when the computer assumes that the seconday injectors come online, so it cuts a bit of fuel to the primary injectors... but due to some electrical problems (could be any number of things) the secondary injectors don't come on as quickly as they should.

On the 86-88's port opening is determined by amount of backpressue in the exhaust.
On the 89-91's the ports are opened by pressure from the air pump..

And yes, the primaries are 4 ports that are always open.

Happy spinning!

 

Primary ports are in the intermediate side housing. Secondary ports are like larger primary ports, but in the front and rear side housings. These together are the four main ports. 84-91 13B NAs also have Auxilary ports, also known as "6-ports" or "5th and 6th ports". These sit above the Secondary ports and are opened and closed by rotating sleeves. They are closed at low RPM and opened at high RPM. The effect of opening them is (1) increases port volume (when charge velocity is high enough to support the added volume), and (2) extended port closing timing to take advantage of the inertia of the intake charge at high RPMs (it closes after BDC, but the inertia helps keep packing in the air/fuel). If it were open at low RPM, the charge velocity would be rather low and the late intake closing would cause a reversion in the intake path when the working chamber goes into compression. Basically, this would reduce low-end power. Conversly, if they stay closed all the time, it's just like not having them at all, but the Secondary ports are smaller than "normal" 4-port engines so you run out of steam on the top end. Properly functioning 6-ports give you some low-end grunt and high-end steam. Early (84-88) 6-ports were controlled by exhaust backpressure. Later (89-91) 6-ports were controlled by the air control valve and the air pump. There is now an upgrade for the stock 6-port sleeves, which dead-end rather severely. Pineapple Racing makes some modified ones with a radiused CNC-machined insert to help turn the air more efficiently. Check them out at Pineapple Racing. If you want to learn more about the engine parts and how it all works, visit my Rotary Engine Illustrated web site and check out the RE101 section.

Hope that helps.

 

Is there any way to mod the 86-88 13b's 5th and 6th ports to operate by the air-pump, like on the 89-91 version???

 

Yes, there is, but dammit, I'm at a friends house and don't have the link on me. Pretty much you tap into the ACV somehow and run a line to an adjustable valve, and from the valve to the aux-ports. Then you rev the engine to 3800rpms and adjust the valve until the 6-ports start opening. I think Travis Shrey's site has this writeup on it. Hopefully somebody will post this link.

 

http://homepage.mac.com/jburger/jaysrx7/6PortSolution/ http://home.earthlink.net/~burntoast/6port.html