I was talkin to the maszda dealership and they told me that the mid 85 13b engines are exactly the same as the ones of the 91...i pretty much KNOW this isn't true...i had a question about activiation of the VDI and the 5th,6th ports on both the 86-88 and the 89-91 and what activates them, i know the 86-88 doesn not have VDI tho...Please shed some light boys

Thanks

-Evan

 

From previous posts I saw, backpressure opens them up, but I could be wrong (this is on the 86-88) and the VDI on the 89+ does it.

 

Just a little advice, most Mazda dealers don't even know what a rotary is. I called a dealer wanting a quote to fix a 5th and 6th port problem on a car that I was looking at (not for them to do the work, but for leverage in price) the service manager tried to tell me that all rotaries only have 4 ports, I laughed at him and asked to speak to someone that knew what they were talking about.
The 86-88 models are actuated by exhaust backpressure. The 89-91's are actuated buy the VDI. The newer system has a number of advantages, if you reduce the backpressure in the exhaust, there will not be enough pressure to open the ports. Also it's more consistent.
You can modify the 86-88 ports to operate off the air pump exhaust with a few parts from home depot (hose T with flow regulators, etc)

 

The shop guy probably just assumed they're the same as the the '85 GSL-SE had the 13B if I'm not mistaken.

 

when I pointed out his error he changed his tone and became very rude, then i asked to speak to someone who knew what they were talking about, anyways no big deal.

 

Funny same thing happen to me on my 86 GXL.
They told me mine was a 4 port motor. And that the actuators was the egr??? or something.

Ian Skacel
88 10th AE

 

WRONG! the aux ports are actuated by the air pump, ECU and soleniod valves. the soleniod sees positive air pressure all the time, the ecu signals the soleniod to open and it sends air to the aux ports. How many times does this need to be explained? VDI is the Variable Dynamic Intake, I.E. short intake runners for high RPM and long runners for low RPM. VDI is activated the same as the aux ports with ECU soleniods and air pump.

84-88 13B exhaust backpressure

 

Some strange notions about auxiliary port operation.All the 89 and up cars I have seen have a solenoid valve which opens to air pressure on the discharge of the air pump to operate the auxiliary ports.The VDI has its own solenoid valve and is separately controlled.
Also the 84-85 fuel injected 13B cars I have seen have auxiliary ports operated by back pressure from the exhaust(as in 86-88 cars).But then what do I know since I occasionally work for a Mazda dealer.Set of *******!

 

OOPS, my bad, I've never owned an 89+ so I just went on what others had been saying, anyways

 

I go with breeze and Six Rotors. Here's a vac diagram. The air pump is not shown, but it powers the VDI and aux actuators on 89 plus. I have a need to know. What rpm the solenoid for the aux actuators opens/???????????????????? Please,not a guess. How about a meter on the solenoid and reving the engine. I tried to download the 89 manual but its not downloading for me and I'm not sure its in there anyway. Here's the jpg:

 

I'll test this out tomorrow night since I have absolutely nothing to do. I'm hoping that the ECU doesn't need to see engine load to operate the aux ports and VDI.

I'll post my findings then.

Joe Breese

 

Quick tip to anyone. Never call the Mazda dealership on advice or parts for our cars. Their idiots. I had a guy up at Mazda try to tell us that Mazda stop making RX-7s in 85 so there was no way we could own an 86 and an 87 so that we had to both have 85s.

 

The 84-85 13B has 3mm apex seals, 2x680cc injectors, and a slightly different intake setup. Runs the same 9.4:1 compression as the 86-88 NA engines.

The -SE engines are in my opinion the most bulletproof rotary engine. My -SE had tons of miles on it and ran perfect, with perfect compression.

 

agreed about the Mazda dealers, they are idiots. They take what they say as fact, then try to rape you on fixes. They're a joke.

 

This is COMPLETELY TRUE!

I went in there with the Mazda part number for the Mazda flywheel locking tool out of the Mazda shop manual... and they told me repeatedly to go to NAPA auto.

No amount of arguing would convince the fine young lady to just look in her computer for the part number that I had highlighted in the damn Mazda shop manual for the 7...

No amount of sanity could prevent me from calling her a few choice names, either.

 

There is no advantage if your 5th and 6th ports are opening at the right rpm (3800 I think?, maybe 4000). If they aren't opening or not opening at the right time due to exhuast restrictions, or a lack there of, you can splice the airpump exhaust with a garden hose T that has adjustable flow, and put an adapter for a vacuum sized line on one of the T's. Put the 5th and 6th port vacuum line that comes up from the exhuast on to the adapter, and get some one to run the car so you can adjust the flow and get the ports to open at the right time
the only time that this is a real advantage is if you have no cats or a free flowing exhaust that has reduced backpressure so the ports aren't opening.
I have never actually done this, it was posted on here like a year and a half ago (before the hacks). I plan on trying this on my next RX-7.