I have finally my RX-7, a 1982 GSL, in my garage and I've started some minor maintenance work, to get acquainted with the car.
After removing the air filter assembly, I found out that a hose, which I understand is a oil feed to the OMP, was disconnected, which explained why the top of the engine was covered with oil. I thought the OMP had gone bad instead, so I was carefully premixing, which should have prevented engine damage.
Anyway, on my way to reassembling the filter, I've found out that the Sub Zero tank hose (red square) is disconnected from anything that I can see. I have the Hayes manual, and I've tried to search online as well, but I find no nozzle where the tank hose should go to.
On the other hand, the idle compensator (I think, see the red square on the filter's case) is not hooked to anything, which may or may not be right.Again, no help from the book. There's no other loose pipe nearby other than the Sub Zero reservoir hose, that I don't think should be plugged into the idle compensator either!





Now
1) albeit used at doing my own maintenance, I've never worked on an RX-7
2) the Haynes Repir Manual is not helping.
so please be patient if I'm talking nonsense.

Question 1 - I'm not happy leaving the Sub Zero hose loose on the motor. Zero chance of starting under -18°C, but regardless, it must go where it's supposed to. Which is where?
Question 2 - is it normal for the compensator to have no matching hose? the nozzle is straight so it may well be, from my understanding.

Thanks for your help.

 

You can find factory service manuals for 1980 and 1985 cars at foxed.ca

I don't remember much of how the stock hoses are routed, but I think the 1985 vacuum hose layout is more similar to 1982:

 

For the Sub Zero, there was a service bulletin to just unplug the wiring to the tank. It never really worked as intended. Just cap it on the carb side and leave the tank in place or remove completely.

 

I pulled my Sub-Z tank decades ago, left the hose attached to the carb, open at the other end (maybe not the tidiest presentation), never a problem...

Stu A
80GS
AZ

 

I believe I've nailed it.
My car's carb was rebuilt by a mechanic working for the dealership who sold it to me. Really nice people, but not rotary experts (neither am I!).
Over the past two days I looked at the rat's nest and eventually I convinced myself that something was wrong, i.e. that the Sub-Zero pipe had been routed into the idle compensator, and this is why after removing the air filter housing I ended up with a free Sub-Zero pipe and a idle compensator nozzle both disconnected. However, I needed proof...
By looking at this diagram, I was able to find where the Sub-Zero reservoir tube is supposed to go.


And guess what is plugged into that nozzle instead? The green dotted pipe, which, according to the diagrams, should plug into the idle compensator instead.



As the car never started below 18°C, it was rather benign - except that, as I found out driving from Denmark, the idle was low, rather reluctant to adjustment.
So I'd say it's time to change piping at start the engine.

 

Thanks Stu A (and others). I posted right before reading your reply. I'd appreciate if you can confirm that what I said makes sense.

 

ILO:
The point where the hose enters at the carb is CORRECT. However, it looks, by your GREEN dotted lines that it feeds into the Emissions "Nest" (aka Rats Nest) which, at least on my 1980 SA Mk1, is INcorrect!
I recall your RX7 is an FB model, so perhaps the FB peeps here can add a comment?

Stu A
80GS
AZ

 

Sounds like you got it all figured out. As you said, the nipple on the rats nest where your green dotted hose is should instead be running to the idle compensator valve on the air cleaner - currently it's running to the cold start assist nipple on the carb, which is, interesting...

For the cold start assist nipple you can either cap it or leave it open. I've found that sometimes it doesn't even pass through to the carb side of things (hence why mine is open). For peace of mind you may as well cap it, but if you choose not to it will not affect performance, it may simply allow a very small amount of unfiltered air through. Not that that's good, but that's your call.

 

Thank you all.
I took her out for a drive and all is good. Honestly, not different from before, but given the conditions this is probably to be expected: it's rather unusually cold outside for the season and it may be that the idle compensator bimetal valve remains shut.

I own two other classic cars and have spent an important part of my professional life working on engines as an electronic engineer (engine control firmware for road cars first, then for F1 engines) - so I'm used at looking at excellence in mechanical engineering, and, albeit with limited experience, I do drive cars rooted in the early '70s and '80s.
My humble opinion is that the engineering around the Wankel is amazing. The 'drivability' of my GSL is absolutely surprising: the engine is so smooth and balanced!
The rat's nest is something that I look at in awe... I must study it in more detail. It's ingenious!