BlaCkPlaGUE

Its on the throttle body, and its NOT for the fast idle cam.

Its connected to the same coolant housing, and its yellow in color. Its plastic with two vacuum nipples attached to it.

I pulled it out of my left over parts bin, and was playing around with it.

With a lighter, I was activating the thermowax to see what it was doing.

Without any heat, the nipples pass air through each other. With heat, the outside nipple passes air through the small little filter on the end and not the other nipple. The other nipple gets clogged with heat, the one towards the threads.

So this obviously activates something upon warmup, what is it?
I was checking over the haynes vac diagrams, its quite the mess, plus I don't see any lines going to the TB..

any ideas?

Just trying to understand the emissions components..

Sesshoumaru

iTrader: (1)

double throttle

NZConvertible

It's called the thermovalve and it operates the double throttle system. It basically switches the vac supply to the actuator on and off so that the #2 secondary throttles are closed when you start a cold engine and then open once it warms up. See FSM pages 4A-53 and 4A-57.

Icemark

Its a thermo valve, not a Thermo wax, and its for the second set of throttle plates. It keeps them closed or partially closed while the coolant temp is below 125F, so that there is less wear on the engine when driving after first starting.

If you have done the throttle bod mod, you have already removed the plates (and should have replaced or spaced the E-shaft thermo valve as well-so you have full oil flow when cold).

Icemark

whoops Jason beat me too it

BlaCkPlaGUE

I see. I will check the FSM when I get home NZ, thank you.

I want to learn this **** so that I can hook it all back up properly. Drivability is IMO much more important than simplicity... I learned that the hard way

NZConvertible

The thermovalve has no effect on driveability at all. It only there to stop stupid people treating their car badly. I'm sure you're smart enough to take it easy on a cold engine so I wouldn't be too concerned about it.

BlaCkPlaGUE

I understand. I want this car back to stock to tell you the truth. I have a few more questions tho..

1)The thermo valve has two nipples, the one that I have anyways. Why does the auto one not have the vent to atmosphere?

2)On the thermo valve, there are two nipples. The one CLOSEST to the threads connects to the secondary throttle plate diaphram with a check valve inbetween. Yet on page 4A-58 it clearly says that the check valve is only for the auto tranny. Yet in the first picture, its showing the MANUAL tranny thermo valve with a check valve??? So is the check valve only for auto, or manual, or both?

3)Final question on the thermo valve. The inner nipple connects to the diaphram, where does the outer nipple connect to? I checked the rats nest diagram and I cannot see it, im confused.

thanks for your time!

BlaCkPlaGUE

Bump.

Still would be nice to know Is it just any vacuum source on the intake?

NZConvertible

I have no idea about the auto versions. It confuses the hell out of me too...

Here's how the 5-spd's double throttle system works. The thermovalve is basically a 3-port valve with one port connected to the manifold (for vacuum), one port connected to the double throttle actuator and one port open-vented via a little filter. Inbetween the thermovalve and the actuator is a check valve, oriented so that air can only from from the actuator to the thermovalve. Both manual and auto TB's have this check valve.

When the coolant is below 140degF air can flow between the manifold and the actuator. When the coolant is above 140degF air can flow between the actuator and the atmosphere. So when the engine starts cold, manifold vacuum acts on the actuator, sucking the #2 secondary throttles closed. Because of the check valve, this vacuum is trapped in the actuator and the throttles are held closed regardless of changing manifold vacuum. When the engine warms up, the thermovalve changes state, the vacuum is released to atmosphere and the throttles spring open.

BlaCkPlaGUE

Well since there is a check valve, how does the vacuum become released so that the throttle plates open? does the check valve actually leak air very very slowly, so after vacuum has been rerouted, the plates slowly begin to open up?

NZConvertible

Sorry, my bad. I put you crook about the check valve.

The check valve is inbetween the manifold and the thermovalve, oriented so air can't flow back into the actuator. The check valve keeps the vacuum in the actuator, the thermovalve releases it when it opens.

This pic shows the NA TB, but it works exactly the same way as the Turbo's.



FYI, this is exactly how the twin-scroll system works too. Instead of the 3-port valve operated by coolant temp, you have a 3-port solenoid valve operated by an rpm switch (the ECU).

HAILERS

Whether it's a automatic or standard transmission car, the valve b/t the double throttle diaphram and the water thermo valve is a DELAY VALV E not a CHECK VALVE.

I'd recommend looking at page F1-35 of the 89fsm that is online. It gives a better view of where the Check Valve is in relation to the Two Delay Valves on an automatic transmission car.

EDIT: FUDGE, that NZ guy posted while I wrote. I'd still take a look at the 89fsm and the picture there.

I still think there is supposed to be a DELAY VALVE b/t the double throttle diaphram and the water thermo valve. See the parts fische. It's there.

NZConvertible

As you can see from the pic, manual TB's don't have a delay valve, just a check valve. Only auto TB's have delay valves (two). That pic is from the page mentioned.

HAILERS

As you can see from this parts fische for a SERIES FOUR car, the manual cars indeed DO have a DELAY VALVE.

It's item 20-309B, and it's for a M/T.

HAILERS

I have other sources of verification if needed. Attached is the other part of the parts fische page.

NZConvertible

Interesting. So putting a delay valve in that location would slow the opening rate of the throttles when the vac is released by a second or two. I guess this is to avoid any surprise power surges.

BlaCkPlaGUE

wow, learn something new every day huh NZ?

I noticed the delay valve as well, and was going to post about it becuase I saw it on the parts sheet that was printed for me at mazda when ordering some other ****. Obviously, I need not to, as its all been answered. Thanks guys!

Ohh oh, next question

The purge valve on the vac rack, that is used to vent positive crankcase air pressure, i've been looking at it and JUST want to confirm how it is hooked up.

The nipple on the far left of it, bigger one, runs to the oil filler neck. The other smaller one, on the bottom, runs to the rear of the plenum vacuum nipple. The valve actuator (top of purge valve) nipple runs along side the other vac tube to the plenum, and plugs in right beside it?

mazdaseenitcoming