drdish

Can anyone tell me what the Shutter valves purpose is? Mine has vacume all the time which I understand means it is bad, but I am not understanding what it does, or with a bad one, what it can cause the engine to do??????

twinkletoes

iTrader: (17)

Its a piece of crap!!! If its bad just clog it with a vacuum plug or something. Its part of the emissions and works for deceleration im pretty sure. It'll will make the engine run bad and make a honking sound with the blue air filter top off while idling.

drdish

Cool! Thanks for the info. Is there anything more to do other than just jam a bolt in the end of the vacume tube?

twinkletoes

iTrader: (17)

You can take the whole shutter valve off, and jb weld the hole it connects to closed, but taking the carb off isn't worth it. I put a vaccum plug in mine and run it real hard all the time for about 3 months so far.

drdish

Rokey Dokey! I will go plug it!

'84-12A-GSL

The shutter valve cuts fuel off to the rear rotor while decelerating, to prevent backfiring, and increase fuel economy.

I have a new intake set up now, so I ripped the shutter valve outa my stock one, when I ported it. And JB welded the hole when the rod used to run through.

drdish

Well, kwith it plugged, the car runs GREAT! holy cow what a differance. She is back and running and purring like all 7's should! Thanks all for the help!

ray green

iTrader: (14)

That's great that you got it running again but if you had fixed the shutter valve instead of plugging it, you would be getting better gas mileage and be putting out fewer emissions. Also you wouldn't get those backfires when you deaccelerate hard.

I wired mine open when I removed my rat's nest a few months ago but the drop in gas mileage plus the backfires plus the increased emissions (can't see them, but I know they are there) are significant, so I will be hooking it back up some weekend when I get a little time (along with the rat's nest - you need the rat's nest for the shutter valve to work).

Just a thought.

Ray

drdish

Thanks Ray! The little I have driven the car tho, it hasnt backfired at all. I agree that the emisions have to be bad, and I will fix that. Just happy to have it running. It's a start.

ray green

iTrader: (14)

I only get the backfires when deaccelating hard, like down a hill or hard downshifting. It is a minor problem, but every time it happens I am reminded that a little bit of gas just escaped the combustion chamber and got wasted.

The loss in gas mileage is significant. I was getting 23-24 mpg for my mostly highway driving before removing the rat's nest and disabling the shutter valve. Now I'm getting a couple miles less per gallon, around 21-22 mpg. That converts to about $5.00 lost every time I fill up the tank, or about $8.00 per week ($400/year). And a similar calculation could be done for the increased emissions.

But hey, if it's running well, that's the important thing. Go out and have some fun!

aussiesmg

iTrader: (1)

The shutter valve is a 3% fuel economy improvement when the throttle is disengaged, no way it can be $5 per tank for this alone, if you lost MPG after the rats nest removal you have a different issue, maybe a vacuum leak, off track but relevant the 2GDFIS ignition made mine pick up about 3 MPG.

Shutter valve removal/block wont increase your mileage by any significant amount IMHO

two79rx7's

I am limited for time so I can only cut and paste at the moment

The following are copies of my posts from the following thead
https://www.rx7club.com/1st-generation-specific-1979-1985-18/car-wont-hold-idle-without-choke-676232/

see the entire thread though for complete circumstance.

my 1st post:
two79rx7's.
I vote shutter valve soleniod.

I think I have a problem here too.
this controls the assoc. coasting valve which works with the shutter valve
See FSM fotr 85 section 4A -6 .17 and 4A -8 .33

coasting valve supplies fresh air into rear primary port when decelerating to prevent excessive vacuum
shutter valve shuts off rear primary port during deceleration

IE: engine is to pull in air through rear primary port by way of the coasting valve during deceleration to prevent vacuum when shutter valve closes off intake manifold feed from carb. If this system sticks open also during idle and acceleration you have a big vaccum leak ( see rx7doctors post ). But this is not the same as a broken hose causing a vac leak

empericaly this is the personality of an engine with this problem

there is a small hole on the inside of the rear drivers side in the air cleaner case with the engine running you will probably hear alot of air getting sucked into that hole. It might sound like a horn blowing. Put your finger over this hole or plug it up with something that wont get sucked in. the engine should now idle without any help.

If your so inclined strip the carb down to remove alot of "stuff" not really needed see

contact vipernicus42 for his excellent pdf tutorial carb strippin
and
see his post " Need a few good *carb* guys for review"

I beleive this covers the coasting valve and shutter valve and S.V soloniod

an additional step after this part is sorted out is to:
remove an aging rats nest which will plug up all potential vacuum leak sources; or you can plumb all new hoses and do a complete diagnosic of this system to make sure it is completely 100%

One post I read said shudder valves go up all the time but I think they are only on later FB's maybe only 85's

One thing I notice with my very similar problem to yours is if I run the 12A car hard at 80 to 85 on the highway which is where these cars shine. for a half an hour or so...really run the car out in 3rd 4th and 5th, then afterward at least for a while your car will at least hold a really rough idle instead of conking out. And if you bump the gas while at a light you can prevent the same.....What you are doing is giving extra gas into the big vacuum leak by way of the accelerator pump enriching the mix enough to keep an idle. This is what RX7doctor was refering too about the vaccum leak.


MY 2nd post
two79rx7's.

Stopped by again to check up on things.

In regards to your question to me Wotnartd, here goes,

Refer to my prior post a few days ago….If you find the condition that I described there, then you’ve got a problem in this pneumatic circuit which means one or more parts are bad and a remedy is needed.

SECTION 1.

There are 3 parts that must work together.

1. Shutter valve solenoid---- an electrically controlled pneumatic solenoid w/ yellow dot on top in rats nest.

2. Shutter valve ( S.V. )---- a butterfly in the rear throttle plate port under the carb ( i.e. top part of intake manifold).

3. Coasting valve ( C. V. )---- .
Is the control valve that regulates the on or off state of air flow from air cleaner into the vacuum of the intake manifold at a location downstream to the position of the shutter valve. The C.V. simultaneously also has an arm that actuates the shutter valve to be in either a closed or open position. The C. V. state is determined by the vacuum signal it gets from the S.V. solenoid

SECTION 2.

Start with diagnostics of the S.V. solenoid with engine off.

On the solenoid:

Step 1.
The port ( 1 ) pointing up and closest to the carb goes to the coasting valve, disconnect the rubber tube on the side of the C. V.
The port ( 2 ) parallel to the body of the solenoid and adjacent to the electrical connector goes to vacuum source at the base of the carb., disconnect rubber tube at solenoid.
Blow through C. V. tube ( 1 ) and air should come out the vacuum port of solenoid ( 2 ).

What does this mean.... vacuum gets supplied to coasting valve when NO power is applied to the solenoid ( hint, engine is off )... See the next step which further confirms why this is true.

Step 2.
Now apply battery power to the solenoid directly with test clips by removing the electrical connector ( I am not sure if you have to worry about polarity, my strong guess is you don’t but check this out carefully by looking at the connector )
Blow through tube ( 1 ) and air should come out of the vent of the solenoid and NOT the vacuum source ( 2 ).

What does this mean.... vacuum gets disconnected to the coasting valve when power is applied to solenoid...right.

Make sure both of these events happen.

*****************

SECTION 3.

Now on to the coasting valve:

Hook all hoses back up….. get engine to idle.
As I referenced in my prior post, plug the hole in the bottom of the air cleaner with something that wont get sucked into it or put a finger over it. Apply or remove this seal as needed while doing the test below. ( Don’t let anything fumble into the carborater!!!). Again this hole is easy to find as it is sucking air in madly and making a horn like sound at you. Remember, it should not be doing this at idle…This is the flag waving at you to tell you there is a problem with this pneumatic circuit.

What is supposed to happen.
At idle, no air should be sucked into this hole. Then bring engine speed up to 2000 or 3000 rpm and then drop the throttle immediately down to idle. Deceleration---this is when air should be sucked in and routed to the intake manifold while simultaneously the shutter valve is closed. Once the engine speed has dropped down to near idle the reverse becomes the correct condition of operation again.

So far , there is still a disconnect in the logic as to how this system works . For instance and directly related to our problem of no idle…Does the S. V. solenoid need to supply a vacuum or no vacuum signal to the coasting valve for it ( the C.V. ) to open the shutter valve and shut off the air source from the hole in the air cleaner on route to the intake manifold.
To further illustrate:
When power IS NOT supplied to the S.V. solenoid, which means vacuum is supplied to the coasting valve, as we found in SECTION 1., does this cause the coasting valve to open the shutter valve and shut off the air source being supplied to the manifold.
Or is it the opposite, the shutter valve closes and air is supplied to the intake manifold.
Without taking known good parts off a car and testing them in your hand, the key is to trace what the power state of the S.V. solenoid is versus the engine operating state. So what is the source of power to the S.V. solenoid?

Ok, I looked through the FSM ‘85 and found
1. The emissions control electrical system for 12A engines section 50 B-1 shows terminal Q on ECU connects to this solenoid for a power source but it does not say what the power state of the solenoid is for any particular operating state of the engine or commented about anything in regards to the problem at hand.
2. ECU state condition, section 4A -44 shows Q at < 1.5 volts when ignition is ON but engine is not running... this is also the initial state when the engine begins to run.

********SO there is the answer.*********

Voltage is not 12 volts, which then must be reserved for the state of the solenoid during the deceleration condition.

An aside:
{ it is possible that it does not follow this pattern but instead }
{ ign. ON - ECU/Q = < 1.5 V: }
{ engine now running but not decelerating - ECU/Q = 12 V: }
{ engine decelerating ECU/Q = <1.5 V: }
{ my vote is this is highly unlikely, just needs to be verified at the car }

To continue:
So voltage is NOT supplied to the solenoid accept for the deceleration condition.
Putting all of the pieces together:
During all conditions other than deceleration a voltage is NOT supplied to the shutter valve solenoid as a signal, vacuum IS supplied to the coasting valve as a signal and the diaphragm in the coasting valve OPENS the shutter valve and DOES NOT allow air to get sucked into the intake manifold through the opening in the air cleaner.

Before, we could have found an offending part by the tests in SECTION 1. and SECTION 2 but the operation of the system state was unknown and determining a suitable remedy was vague at best. Now its all very simple.

For instance:

1. Is the shutter valve solenoid stuck as though it has voltage supplied to it and has disconnected the vacuum signal to the coasting valve? This would shut the shutter valve ( now the word shutter valve starts to make sense ) and cause air to be routed to the intake manifold when not wanted and would kill the idle. Also is the ecu electrical signal bad or is there a problem with the wiring shorted to hot ( always giving a 12 Volt signal to the S.V. solenoid ), this would give the same result.

2. Is there a hole in a vacuum tube to the coasting valve? Same result

3. If none of these conditions exist, then the coasting valve diagram, or the coasting valve actuating arm or the shutter valve is defective in some way. This will require installing a working coasting valve and/or repair of the shutter valve

4. It is possible all of these conditions can exist at the same time or each exist intermittently and independently, so be though.

5. If 1. and/or 2. exist then an immediate simple solution would be to hookup a good piece of vacuum tubing from an always on vacuum source DIRECTLY to the coasting valve as a signal to cut off the air source to the intake manifold and OPEN the shutter valve. Just plugging the air source to the intake manifold as described earlier will allow the engine to idle but it wont open the shutter valve. This will for all intents and purposes block supply from the rear primary port of the carb. intake port until the shutter valve can open.


Vipernicus42 reports he finds shutter valves become seized in one position over the years. Check this out some time when you can because if this has happened and is fully or partly closed you will never get balanced flow between front and rear primary ports for all but granny driving.
He also reports to this effect ( just from memory, ‘the reason for the design of the shutter valve was to eliminate backfiring during deceleration . However if everything is tuned right there should be no backfiring to warrant a shutter valve.’

I have a 79 rx7 which backfired to the extreme! There is no shutter valve on these manifolds. It was being serviced by a Mazda tech at a dealership at the time….they never got it right…. only worse. I will vote that the dealership did not know what they were doing.

My recommendations contact Vipernicus42 to get his excellent tutorial
Stripping a Stock Nikki, The essential guide to removing the extra crap
from a stock rx7 carburetor.

Get a second Nikki and for a baseline install it to see how it functions then clean and rebuild it ( as an aside, never touch the floats unless absolutely,,absolutely did I say absolutely!!! necessary ) but include selectively the changes or modifications you want as shown in the how to step by step tutorial above.
You will always have your original nikki to fall back on or refer to.

For instance depending on my final goals I may want to keep the shutter valve operating if I need to set other aspects of the operation of the engine which could promote backfiring. In my ‘85 12A car.

On an aging car, remove the rats nest or rebuild it to 100% spec. if you are going to keep it. The above is an excellent example why you need to do one or the other.

I should be able to let you know what my findings are for what the voltage signal state is to the S.V. solenoid by checking my car in the next few days to confirm that point.

Note how the FSM leaves you in the dark about all of this, it only spells out the go or no go tests to trace if a part is faulty and it did not cover all of the components involved.
A small chapter with a summary explanation of each system would have made the FSM much more complete.
As an example I will repeat from above:

*******************
“Putting all of the pieces together:
During all conditions other than deceleration a voltage is NOT supplied to the shutter valve solenoid, vacuum IS supplied to the coasting valve and the diaphram in the coasting valve OPENS the shutter valve and DOES NOT allow air to get sucked into the intake manifold through the opening in the air cleaner.”
********************
I probably need to edit this more but for now just wanted to get this posted.

I hope this meager attempt above will:
Help anybody to understand the operation this particular system and to allow them to modify it in any way they choose and,
Give anybody a path to follow so they can compartmentalize and understand the operation of any other system. To lay out the areas you do understand and to present it so you can ask questions for the parts you don’t understand.

Two79rx7’s

P.S. any comments are always welcome.





my 3rd post
two79rx7's.
if this did not help my next best guess is:
the anti afterburn valves 1 + 2 which sends air into ports during decl. just like coasting valve. so if defective same problem. see 4-A .5 for decription
check idle compensator in air cleaner ***. 4A-.51
check altittude compensator see 4A .51

Hope all of this info helps to get a handle on your situation.

regards
two79rx7's

end of copy************

let me know if this helps
two79rx7's

dbragg

iTrader: (7)

i locked mine in wide open position a couple months ago. after i put the manifold and all back on it now idles at 1400. it hasnt really bothered me much. i bought a can of carb cleaner and sprayed it all over the manifold and carb to try to find a vacuum leak, but i didnt find anything. oh well

ray green

iTrader: (14)

If you really want the truth about the value of a shutter valve, look in two79RX7's post, I'm sure it's buried in there someplace.

But my 10% drop in gas mileage after removing the rat's nest and wiring the shutter valve is a real measured fact, not a theory or opinion. And there were no vacuum leaks before or after removing the nest - one of the nice things about getting rid of the rat's nest is it makes finding vacuum leaks a cinch.

So it seems to me that the shutter valve is the most likely culprit and at the very least I'd like to lose the backfires and reduce the emissions, so that alone is a good reason to hook it back up. Also even a 3% increase in gas mileage would be worth having. But reinstalling the whole rat's nest is probably what's needed and that's what I'm planning to do.

AWS, do you mean you can't readjust the idle below 1400 after disabling the shutter valve? That high idle would annoy me, I worked hard to get mine down to a smooth 600 rpms, just feels and smells better at stop lights.

dbragg

iTrader: (7)

yeah. its been that high since i moved to oakwood. i did the work right before i moved. it doesnt really bother me that much, so ill get around to fixing it eventually. my neighbor has a 79 manifold i may get ported and cut up and put on my GSL some time soon. i just need to find someone to cut on it for me, or possible cut on my FB manifold.

ive just got used to it. i cant really hear it due to my radio. outside the car you cant really tell due to the borla its rather quiet. i have noticed a fall in fuel economy though. not major, but noticable.

two79rx7's

if you look at the pneumatic circuits of the rats nest and related parts you will find you wont need to hook everything back up for what you seek.

ray green

iTrader: (14)

I was wondering if I could just reinstall the shutter valve solenoid without the others and I asked about it in another post, but nobody seemed to know how to do it, I guess because nobody has tried.

I am not very good at reading electrical diagrams, not enough patience, so unless someone can walk me through I'll probably just go with the whole rat's nest reintall, it may have some other benefits (like even more increase in gas mileage and reduction in emissions) that I also don't understand.

But thanks for the suggestion two79's, it's an interesting idea.

two79rx7's

Ray
If you read through what I wrote it will hopefully fill in all the holes on the why's and how's the FSM leaves out as well as the disjointed way the FSM presents the info.

read through my posts a few times and refer to the diagrams on the FSM.
Make it enjoyable and get something to drink or what have you.

The circuit basically routes air only into the rear rotor on decl instead of air/fuel mix.
At any other times you dont want this to happen.
All in all not such a bad proposition.
Remember with a long decleration time you will have a ( in a relative sense ) cold rear housing and rotor. It is also known that stepping on it with an engine not fully warmed up is bad. So in the case of mountain climbing and and miles of drifting and braking down the other side, then only to climb another mountain ect., a manual override in this circuit seems reasonable. Reading through everything I wrote you would know everything you need to make this easy mod.

After you understand how and under what conditions the shutter valve solenoid actuates the coasting valve and shutter valve you can learn its "personality" with the telltale signs when it is acting up and you can diagnose when it is not working right and where the fault is. With confidence you can tear into it and fix it.

hope this helps
regards
two79rx7's

ray green

iTrader: (14)

Thanks two79's from me and the other lurkers who aren't quite ready yet to admit the shutter valve is good for something. Your simple straight forward explanation makes a lot of sense and is very helpful. And I might even take on your more detailed post when I go to work on it this weekend.

Ray

two79rx7's

Sometimes a good idea is to give yourself an out by working on a spare part, just in case an old part snaps and is then non repairable and strands you.

otherwise its just a matter of patience and fun


One idea I want to try is for the gas millage enthusiasts. There was a great thread
which I do not recall at the moment the author but he was getting over 30 mpg.
What if at highway speed on flat road you manually kick in the shutter valve and coasting valve to operate.. at say 3000rpm which should give good momentum. You will be 1. running on and generating power only from the front rotor. The rear rotor will 2. generate a power loss condition due to pumping losses and friction ( more on that ). However the composite condition of 1. and 2. may still allow one to ooozzz down the highway at 60 mph using much less fuel than if both rotors are "hot".

THE PROBLEM: WERE ARE YOU GETTING YOUR LUBRICATION FOR THE REAR ROTOR FROM. IT WONT COME FROM PREMIX. SO THE OMP HAS TO SUPPLY IT DOWNSTREAM (OR AFTER ) THE SHUTTER VALVE.
this part is so important for all of the premix guys under any condition with te shutter valve. I will have to check where the oil meter pump oil is injected, so a change may be needed here in the manifold.

So many things to try, so little resources and time.....

regards
two79rx7's

GREG5656

My 79 RX7's Tac pointer would bounce up to 1000 rpm's to 1500 plus and down again in less than a second time interval. The problem was not my wiring, it was the Distributor "Points Plate" that was lifting upwards by a 1/4 inch. Remove the 2 screws holding the plate down, and lube the bearing under it, and the weights also. (My bearing were bad, I did not feel a smooth rotation of the plate after lubeing it)...This lifting of the plate, caused the trailing points rub block to touch the cam prematurly, making the points open too soon. Test this by lifting the plate with your fingers at one end and watch to see if your points open and close. . .This opening made my RPM gauge to be unreadable, and Yes my timing was not the best and it really was the timing issue that led me to shim the plate which gave me a steady timing dwell and consequently a Tac that now reads steady. I shimmed the "Point Plate" with a thicker washer at the hold down screw, to hold it downwards preventing the 1/4 inch upward lifting, but, remember the plate must have a gap under it for the vacuum advances of the Leading & Trailing to move freely. Greg5656

DivinDriver

iTrader: (15)

4 years, 7 days... not quite as good as your other.

(PS; checking the thread age before replying is good practice...'specially when posting the same reply more than once.)