Greetings fellow rotorheads,

I was perusing my 1989 RX-7 FSM and on page GI-10 there is an acronym key. Listed in this key is "VRIS." As far as I've been aware, rotary engines do not have the VRIS system (though the 5th/6th ports+actuators in N/As could be compared, though they're not the same.) Am I incorrect? Is/was there a VRIS system in the 13B/13BT engines?

I am familiar with the Variable Resonance Induction System (a pretty nifty way to make low-end torque and high-end HP w/o messing with the timing). I currently drive a '96 Probe GT (w/ the KL-DE engine, a nice Mazda-designed V-6) as my daily-driver and I do not see anything even remotely resembling the VRIS on the PGT in my TII.

Am I just blind? Are the 5th & 6th ports actually a VRIS system? I haven't been able to look at a N/A RX-7 for a while--not since I sacrificed my '89 GTU over two years ago.

I have not found any other references to the VRIS in the FSM. I will admit that I have not read every single page, but the FSM isn't exactly leisure-reading material.

 

The VRIS system I believe was incorparated into all the 13Bs. I remember reading something about it somewhere. It talked about how the Intake Manifold w/ the 5/6th ports work as the VRIS system. I might be wrong but thats what I remember reading about it. It was quite a while ago, about 3yrs ago.

 

Hmm, so the 5th/6th ports ARE actually the VRIS system? Sweet... the 13BTs don't have those ports though; so that explains why I couldn't find them on my TII. (I'm still pretty new to the 13BT... I'm learning; it's not that much different than the 13B)

Thanks; I had a feeling it was in fact the 5th/6th ports--I just never hear of any rotorheads speaking about them as the VRIS. They're commonly just referred to as the 5th & 6th ports.

 

It has something to do w/ the way the intake manifold is setup and the ports opening at 3800rpm. I saw it in my haynes manual somewhere, but my dog ate that about 6 months ago. Damn dog.

 

Yeah, it's a similar setup to how the VRIS in the Probes and MX-6s work. VRIS actuator #1 opens at a specific RPM, then closes at another, same with actuator #2 (but they open/close independently of each other, controlled by the ECU). Designed to change the harmonics of the intake of air in the intake manifold being injected via the injectors, it helps with the flow of intake air. Think of a flute and how the note changes as you cover and release various holes--it helps the air flow faster and more efficiently through the IM. Cool idea. Couple that with variable timing and that would be one hell of a V-6. Some Porsches use the VRIS technology too, IIRC.

I didn't realize that that was the same purpose for the 5/6th ports. Considering how the rotary engine doesn't use injectors, I thought the concept was similar but not the same. :shrug:

I have a Chilton's for the RX-7, and the FSM too. Perhaps some more technical reading is on the menu for tonight. :spin: