apeckz

I recently purchased a 1985 GS - odo says 100k but I have no reliable history. Car started and ran, but had virtually no power - even on flat road - did not even consider taking it out of the subdivision.

After removing the carb and intake manifold I found that the linkage between the shutter valve and the associated butterfly valve had been disconnected. The pin and circlip were laying on the manifold. The butterfly was free to moved to whatever position conditions urged it.

The linkage that connects the butterfly shaft to the shutter valve is worn out, meaning the holes for both pieces of linkage are severely elongated. I remedied this by enlarging the holes and using a larger pin. I am not certain that the valve works, although it passes the tests described in the Haynes manual.

The shaft that extends out of the shutter valve has about 1/2" free play when no vacume is applied to the valve. This permits the butterfly to move past the wide open position and partially close-in the wrong direction of course.

Do I need this valve?
Can I simply lock the butterfly in the wide open position?
What adverse effects would this have on engine behavior?

BTW, it was interesting to verify that a coolant leak was due to deteriorated and broken orings between the manifold and the engine.

Thanks,
Bob

Pele

iTrader: (28)

It's not needed... but if it isn't sucking down air at idle or making the goose noise, It should be good.

jayroc

I replaced my shutter valve and it did not resolve my problem which was a looping idle. The real problem was there was too much play in the shaft and throttle plate. I consider it a very difficult task to remove the throttle plate screws to replace the shaft and plate. So, if I were you, I'd plug the valve, and make sure the plate is in an upright position, then bolt everything back together. But if you insist on replacing those items, I got a plate and shaft I bought from mazdatrix. They're unused and I'll sell them to you for $20 shipped if you're interested.

SilverRocket

The shutter valve is a common source of problems, and is good for nothing - if it's working right (and that's a big if), closed throttle deceleration will be a little rougher without it, but it's not a big deal at all. Best to disable it or remove it completely from the manifold (seal it up with JB weld).

Actually, the same can be said for the entire emissions control system (rat's nest as it's nicknamed). It's a big mess that's pretty much only good at causing trouble. It's entirely unneeded - the engine will run better/smoother without it. Ditto the vacuum advance mechanism that's part of the nest.

The only thing worth keeping is the PCV system, meaning the charcoal canister, a line to the intermediate housing nipple, and some kind of air source (filter or line to the air cleaner) on the oil filler nipple.

Most of us are running header exhausts (huge improvement), meaning that we have removed the air pump, ACV, etc. Some of us run aftermarket carbs, which simplifies things *greatly*. I highly recommend relegating that stock Nikki carb to a box in the basement LOL. Simplification is of course secondary to the huge performance gain, but it makes the car a joy to work on, which I sure wouldn't say about that Nikki.

Very common - make sure that you replace with genuine Mazda o-rings, not generic parts store ones.

j9fd3s

iTrader: (3)

the shutter valve is to keep the catylist temps down on deceleration.

mike

85RX7GS

iTrader: (1)

Yes, but it's not recommended if you have to have your car e-checked.

jeremy

iTrader: (1)

told you you'd get better answers here.

SilverRocket

That's true - however replacing that whole mess with an RB short primary system, but with a nice modern high flow cat center-section, will result in better emissions than stock, still sans rat's nest. You could always hook up the vacuum advance for emissions testing if you wanted to. Check out back issues of SCC's project FB for an example of this.

Mind you, a visual inspection could likely fail. Which of course is ridiculous, because if the car is emitting less than stock there's hardly a problem.

apeckz

Thanks all-and Jeremy for getting me here.

I will lock the butterfly wide open, plug the port in the manifold, and take it through the IM240(?) emission test.

I have owned ten or so RX7s-about 50/50 1st & 2nd gen. I have never energized a rotary due to emmissions concerns. (I did do the unmentionable-my '91 was a hoot with 275 HP and 300+ Ft. Lbs. of torque).

Thirty years ago I would have swapped equipment once a year, but now my body objects to even minor bending and getting up & down. Still, I think I will enjoy another 1st gen for a while!

Just for a laugh-I had my MBA and was working 9-5 when the first RX7 hit the U.S. I remember seeing one on the street in downtown Chicago, and it was love at first sight. It took almost ten yearsw until I could buy a well used 1979 (whatever the top model was w/leather, etc).

jeremy

iTrader: (1)

1979 gs. welcome to the family. there is a ton of knowlege here. especially in the 1st gen area.

85RX7GS

iTrader: (1)

The emissions would be lower? Do you have any credible evidence to back this up? The reason I ask is because if it positively effects the e-check, then I would be interested in removing all that stuff.

j9fd3s

iTrader: (3)

thats all they did to the project scc car, put a header and cat on it. they left the rest of the stuff alone. in fact they replaced the shutter valve in the article too

mike

SilverRocket

Ahh... good point about the SCC car, I'd forgotten that. Yes, I am talking slightly out my *** LOL....

The reason I emphasized it, is that as I recall the SCC car made *substantially* better emissions than stock - like, truly remarkably low emissions levels. I am assuming the reason for this is the much improved cat - not the rat's nest doing much of anything.

The thing is, speaking of an emissions testing procedure, I don't see why removing any of that crap would affect much of anything, other than of course the vacuum advance. I could be totally wrong lol.

My car backfired and shot flames incesantly with the rat's nest and shutter valve - completely went away when I removed them. As in, not one backfire ever. (My current Dellorto setup on the other hand, shoots flames, but not as much as before).

Of course, mine weren't working right, but since I see a lot of people on here talking about their flames/backfires with stock carbs and RB exhaust, I'm inferring that many of theirs don't work right either. I don't think very many of them do anymore.

So my inference was that, I'd bet that a good highflow cat as the center section of an RB setup would yield better than stock emissions (because the cat is so much better). I'm unsure whether an airpump would be required, I've heard different things about that. But if it was possible to just run a cat by itself like that, without any other considerations, I'd bet the results would be quite good (until the cat melted lol). Even if the cat were not feasible to run for years without the airpump (I remember Rxtasy on here saying his cat melted after some years.... unsure of which brand it was), it would still be a viable alternative, as an easy swap for the e-test day (ie. make it interchangeable with the RB presilencer.)

These are all just ideas lol, take them for what they're worth.

MIKE-P-28

iTrader: (1)

shutter valves purpose is to choke off all fuel/air mixture to the rear rotor under decelleration, has nothing to do with the catalsyst or the like. its mearly for emisison purpose only, and in my opinion its an evil POS.

Now when you say linkage, I think your meaning the OMP (oil metering pump) it the device on the very front of the carb, or on the rear? kinda in the middle?

apeckz

Mike:

I meant the linkage that connects the shutter valve to the shaft that holds the butterfly valve.

I have drilled the bolts out and removed the butterfly and the shaft. Tomorrow I will get a bit of aluminum rod and use it to plug the two holes that are involved with this system.

I do think the cats from the 90's are more efficient than the stock setup-and that replacing the convoluted stock setup with a single cat will mask the emmissions that will result from this mod. Unless someone has done this with unsatisfactory results, I am going this route.

j9fd3s

iTrader: (3)

dont make me bust out my graphs, it keeps the cat from overheating (more)

mike