Sorry if this is thread already exists but I'm stumped. So I just purchased my very first turbocharged car that also happens to have a rotary engine in it. It's an '88 w/ S4 or S5 13BT swap (not sure which one yet...haven't even had the car a week yet.) Upon driving this with my music off, I found that there was a rattling sound coming from under the hood. When i checked the engine and around in the bay I noticed an unknown part missing. The location of the part is on the passenger side of the motor way below the intake manifold and to the left of the fuel pressure regulator. Its about a dime to nickle sized hole with 2 bolts sticking out. Luckily, the gasket was still sitting there and that gasket is less than 1mm thick, between 1 1/4" to 2" long and less than 1" tall. I don't know if any of the information above is necessary after this next bit of info, but there is a sensor (guessing the MAFS) that is still attached to the downpipe that the connector is just sitting on the wheel well not attached to anything. I'm guessing that those two things are connected, but this being my first rotary, again I am not 100% sure. If pictures would help, I will take some pictures of the sensor and the area with the missing part and post them for everyone within the next few days. I'm not the most mechanically knowledgeable person (yet), especially with rotary engines, so any input will help. Thank you so much guys.

 

Take a picture.

 

Well I'm retarded, and it was definitely was not the MAFS, but that's another problem...gotta chase back a corroded wire and replace it, MAFS is currently not connected, haha. maybe that's why the car gets 16mpg when I drive it like a grandma. Well anyways, heres a succession of pictures going towards the problem area to show where exactly the part is located from the basic overview of the engine bay from the passenger side, plus the gasket that was just sitting on the bolts when I found this. Hopefully this helps solve the mystery of what I'm looking at.

 

That's the hookup for the split air pipe, which feeds air to the catalytic converter when the split air solenoid is open & the engine is under 3,500 RPM. I can see an aftermarket downpipe on your motor, so I'm going to guess you have no cat either. If that's the case, and you won't have to smog the car, don't worry about it. It can be left open to vent off pressure from the air pump, or blocked off. Mine is currently open to the world just like that.

 

Ok, awesome...I was a little worried about that. I'm still learning everything about engines in general, let alone rotaries. Thanks so much for the help. So I've looked around the forums and haven't found anything for these things either but I have a couple more questions for anyone who can help. First one is, and I'm guessing that's what the part is because I haven't been corrected yet, but in the second picture to the right you can see my MAFS just sitting on some more wires up top. It's not connected, the other side of the wire got corroded and it fell off. Is that why I'm getting crappy gas mileage? I don't race the car, in fact I drive it like an old lady, and have only gotten into it a few times...Also, does that have anything to do with the white smoke that I only see around 6k rpm's? Question number 2 is, at 6k+ rpm's (havent gone over 7k) the car makes a honking noise when I shift. Is that my BOV making that weird noise? It's an HKS SSQV, and I haven't heard that any other time but the 2 times when I've taken the car over the 6k rpm's. I know it's kind of off topic, but seeing as how that first question was so easy to answer, I don't want to litter the board with a bunch of tiny random questions...

 

That should be the buzzer telling you to shift. Mine screams at me well before the redline.

 

What you're calling a MAFS (?) is the oxygen sensor, the green plug connects to a white plug that comes off of the engine harness under the intake manifold. Without it plugged in, the ecu never go into open loop, and this will hurt fuel economy.

And as was mentioned, the buzzer is a redline warning. It goes off at 6800 RPM, even though redline is 7000 RPM.

 

Again, I'm currently anything that's not body or paintwork retarded..I was thinking it was my mass air flow sensor...I was completely thrown for a loop on the noise though. My shift up light doesn't come on ever so I didn't put 2 and 2 together...It just sounded like I sat on a duck. That's all I got for questions on this thread though. Hopefully you'll see how hopeless I am and search out more of my threads to make sure I'm not dumb forever. Dont wanna give a bad name to rx7 owners...Anyways, thank you so much guys for the input and putting up with my n00b status. Take it easy.