shutter valve what does it do?
 

been trouble shooting my running issue, and removing some of the extra stuff on the carb. ended up finding that the shutter valve is just a huge vac leak when activated (causing the running issue) I see some people remove or plug it up witch is great, but what does it do?


also on the rats nest there are the two solenoids for the vac advance, i see that people remove them and just run vac lines to the vac pots. why are the solenoids there? is having the pots hooked up directly going to cause the advance to work differently?


thanks rob.

lots of looks, but know one knows?

Shutter valve closes during deceleration. When closed it blocks the intake path to the primary port of the rear rotor. Many cars are running with the shutter valve plugged. When the lines are plugged the intake path stays open full time.

The Vacuum advance solenoids cut the vacuum to the advance diaphragms when decelerating. All these solenoids relate to emission control.

Shutter Valve Open (no vac)
http://intertron.com/ron/images/sv.jpg


Shutter Valve Closed (vac/deceleration)
http://intertron.com/ron/images/sv1.jpg

shutter valve is there to turn off the rear rotor on decel, this keeps the temps in the cat from spiking up. think of it like fuel cut on an EFI car.

mazda has the vacuum advance solenoids so they can turn the advance on an off. basically they turn the advance off at zero throttle. so they have retard on decel, just like the rx8, and the "normal" idle timing. the idle timing is for emissions, the decel timing is to keep it from bucking.

thank you guys.

I get the shutter valve 100% now, and under stand why Mazda put the dizzy on solenoids.

but will running the dizzy with out the valves effect the way it drives? or is just a emissions thing. I would love to ditch the whole rats nest. but if it will run better with them on there I will leave them.

bypass the solenoid real quick, and see what you think

ok then! lol I will!

If you are going to leave the valve in place then no point in bypassing the solenoid. The Shutter valve does noting harmful to performance other than being a throttle resitriction. I pulled mine in one of my F cars years ago and epoxied in a bolt into the shaft holes.

agreed, but my actuator only acts as a huge vac leak when activated. so I think for now till I rebuild the carb I will remove the vac line and lock it open.

the shutter valve works in conjunction with the coasting valve. while decelerating, the shutter valve closes and orevents fuel/air to the rear rotor. to prevent surging or backfiring, the coasting valve opens and sends fresh air into the rear rotor. kind of a neat little system.

to the op, mine was doing the same thing and i just plugged it up and removed the rats nest. its completley opposite of what i thought would happen cause now ALL my backfiring and flames that i got before just stoped once i removed all that stuff...huh who knew?

cool the car just got coverd in a foot+ of snow, so it will be a day or so till i can go at it again. crazzy vt weather it was 60-70 last weakand, then 30's all weak and snow for 3 days, and they say it will hit 80 this Sunday.

plans for this weekand if the snow is gone is to remove the rats nest completely.

Great pics above - my linkage is obviously missing which is why my valve is just flopping around and my car doesn't idle. I think I'm going to try and keep it factory by replacing. I read the page from www.mazdatrix.com/faq/shutter.htm on the shutter valve and they show two bent 12mm wrenches, but make no reference to a part number or where those can be purchased. Does anyone know where I can get those? I suppose I could bend and weld, but I'd rather just own the tool.
Alternately, could I just use a claw-foot wrench and some universal socket drivers to accomplish the same thing?

OK - just found the info on using a distributory wrench from another thread on carb removal (https://www.rx7club.com/1st-gen-archive-71/fuel-intake-10-minute-removall-nikki-carb-448284/), however I'd almost rather use the wrenches pictured on mazdatrix.com if anyone knows where I can get them.

back in the day mazda sold those.

ive actually had pretty good luck with just normal wrenches, worst case you can undo the 2 bolts holding the vacuum rack in and remove it